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ISAAC NEWTON: The secretive, vindictive, paranoid genius p.28

DECEMBER 2019

The world’s best-selling astronomy magazine

EXCLUSIVE BY ALAN STERN

RETURN
TO PLUTO!

A planned orbiter could
revolutionize our knowledge
of that distant world p. 20

Memories of
the Great South
American Eclipse

p. 44

STARMUS V BINOCULAR BOB BERMAN’S www.Astronomy.com Vol. 47 • Issue 12
ROCKS IN TREATS FOR THE CANINE
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Online Content Code: ASY1912 DECEMBER 2019
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VOL. 47, NO. 12
to gain access to web-exclusive content

ON THE COVER

The proposed Pluto orbiter mission
would explore the entire Plutonian
system in detail. RON MILLER FOR

ASTRONOMY

CONTENTS 44 COLUMNS

FEATURES 36 52 Strange Universe 16

20 Sky This Month Starmus V rocks BOB BERMAN
in Zurich
Return to Pluto! Gas giants bid a fond farewell. Secret Sky 18
The fifth Starmus Festival, an
Researchers already are MARTIN RATCLIFFE AND international celebration of STEPHEN JAMES O’MEARA
planning an ambitious ALISTER LING science and music, assembled
spacecraft that will orbit an all-star cast of astronauts, Binocular Universe 62
the mysterious world. 38 Nobel Prize laureates,
musicians, and scientists. PHIL HARRINGTON
S. ALAN STERN Star Dome and
Paths of the Planets DAVID J. EICHER For Your Consideration 64
28
RICHARD TALCOTT; 68 JEFF HESTER
The oddities of ILLUSTRATIONS BY ROEN KELLY
Isaac Newton Ask Astro 9
44
Revered as a great thinker and How is Phoebe different? QUANTUM GRAVITY
scientist, he was also obsessive, Chasing a
secretive, vindictive, and Chilean eclipse Everything you need to
paranoid. RAYMOND SHUBINSKI know about the universe
Peruvian nights, Incan sites, this month: Jupiter’s
and coronal lights were all on collision history, three
full display during my recent new exoplanets, India’s
adventure through South failed lunar lander, and
America. JAKE PARKS more.

ONLINE Venus Globe Trips and Dave’s My Science IN EVERY ISSUE
FAVORITES Get the hottest Tours Universe Shop
globes around. The inside From the Editor 6
Go to www.Astronomy.com Travel the world scoop from Perfect gifts for Astro Letters 8
for info on the biggest news and with the staff of the editor. your favorite New Products 66
science geeks. Advertiser Index 73
observing events, stunning photos, Astronomy. Reader Gallery 70
Breakthrough 74
informative videos, and more.
Astronomy (ISSN 0091-6358, USPS 531-350)
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FROM THE EDITOR

Astronomy’s Editor David J. Eicher
mad genius Art Director LuAnn Williams Belter

Follow the Mention “Isaac Newton” at an astronomy gathering or a EDITORIAL
Dave’s Universe blog: star party and you’ll invariably get one response: He was Senior Editors Michael E. Bakich, Richard Talcott
www.Astronomy. a genius, but also a little bit nuts. Perhaps the two go hand Production Editor Elisa R. Neckar
com/davesuniverse in hand, as psychologists, amateur and professional, have said since Associate Editors Alison Klesman, Jake Parks
Follow Dave Eicher the dawn of time. One thing is certain: Isaac Newton was one of the Copy Editor McLean Bennett
on Twitter: most influential thinkers in world history, and we still owe much Editorial Assistant Hailey McLaughlin
@deicherstar of how we see the world and the universe at large to him.
Born on Christmas Day 1642 (new style calendar: January 4, ART
1643), Newton was premature, a small child whose mother said he Graphic Designer Kelly Katlaps
could have, at birth, fit inside a quart mug. Living with a grand- Illustrator Roen Kelly
mother and disliked grandfather during his youth, Newton com- Production Specialist Jodi Jeranek
piled a list of misbehaviors that included threatening to burn his
family and the house over them. CONTRIBUTING EDITORS
Nonetheless, he secured entrance into Trinity College, Bob Berman, Adam Block, Glenn F. Chaple, Jr., Martin George,
Cambridge, and supplemented his college teachings with additional Tony Hallas, Phil Harrington, Korey Haynes, Jeff Hester,
lessons of his own, including Descartes, Galileo, and Kepler. His Alister Ling, Stephen James O’Meara, Martin Ratcliffe,
ambitious intellect continued, and by 1669, Newton had succeeded Mike D. Reynolds, Raymond Shubinski
his Lucasian Professor of Mathematics at Cambridge, taking over
the prestigious, named chair. SCIENCE GROUP
Despite a lifetime of cranky, unpredictable actions — and avoid- Executive Editor Becky Lang
ing personal relationships with women throughout his life — he Design Director Dan Bishop
focused on nature and everything he could determine about it. His
1687 book, Philosophiae Naturalis Principia Mathematica (called EDITORIAL ADVISORY BOARD
Principia for short), still stands by most scientific analyses as the Buzz Aldrin, Marcia Bartusiak, Jim Bell, Timothy Ferris, Alex
most important book ever written. It substantiated physics and laid Filippenko, Adam Frank, John S. Gallagher lll, Daniel W. E. Green,
down the physical laws of the universe, which were only modified William K. Hartmann, Paul Hodge, Edward Kolb, Stephen P.
in sophistication by the time of Albert Einstein. Maran, Brian May, S. Alan Stern, James Trefil
In this issue, Ray Shubinski’s astronomical biography of Newton,
“The oddities of Isaac Newton,” provides plenty more stories and Kalmbach Media
anecdotes. You can read it beginning on page 28.
Speaking of mad genius, I want to tell you about a new product Chief Executive Officer Dan Hickey
Astronomy has launched, one that is grabbing people’s attention Senior Vice President, Finance Christine Metcalf
beyond our wildest dreams. “Astronomy’s Space & Beyond Box” is a Senior Vice President, Consumer Marketing Nicole McGuire
subscription box filled with cool stuff that will help you enjoy, cele- Vice President, Content Stephen C. George
brate, and admire your hobby more than ever. You sign up, and for a Vice President, Operations Brian J. Schmidt
Vice President, Human Resources Sarah A. Horner
small fee, receive a quarterly box full of astro
and space goodies — handpicked by Senior Director, Advertising Sales and Events David T. Sherman
yours truly — that will make you Advertising Sales Director Scott Redmond
smile. For complete details, Circulation Director Liz Runyon
see spaceandbeyondbox. Director of Design & Production Michael Soliday
com/genius. New Business Manager Cathy Daniels
See you in the universe! Retention Manager Kathy Steele
Single Copy Specialist Kim Redmond
Yours truly,
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6 ASTRONOMY • DECEMBER 2019

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ASTRO LETTERS

NGC 362 is just one of Globular clusters, tackled Can’t wait to see the next mystery solved. — Shoba
150 globular clusters
in the Milky Way Great article in the August issue Kaicker, Toronto, Ontario
galaxy. NASA of Astronomy magazine on globu-
lar star clusters. As a professional The coming smackdown
We welcome and amateur astronomer for
your comments over 40 years, I have viewed and On page 11 in your June issue under your Quick Takes
at Astronomy Letters, studied globular clusters exten- section, you write, “According to data from the Gaia sat-
P.O. Box 1612, sively. I recently retired from the ellite, the Milky Way will collide with the Andromeda
Waukesha, WI 53187; University of Hawai‘i but still Galaxy in some 3.9 billion years, not 4.5 billion years as
or email to letters@ maintain an observatory on Kaua‘i. I have seen all of previously thought.”
astronomy.com. the globular clusters you discussed, except 47 Tucanae,
Please include your which doesn’t come above the horizon from Hawai‘i. Well, I think you guys have that backwards from my
name, city, state, and reading of a February 2019 paper by van der Marel et al.
country. Letters may — James Dire, Peoria, IL titled “First Gaia Dynamics of the Andromeda System:
be edited for space DR2 Proper Motions, Orbits, and Rotation of M31 and
and clarity. Solving mysteries M33.” In it, they write, “The MW and M31 are still des-
tined to merge. However, both the timing and the
Astronomers have relentlessly searched the skies, and impact parameter of the first encounter have increased
the result is a multitude of surprising images that … from … ~3.9 Gyr to ~4.5 Gyr …” — Scott Harrington,
dazzle us, giving us some answers, but not all. Your
articles by renowned astronomers, astrophysicists, and Evening Shade, AR
observers are mind-blowing. The July special issue on
the Apollo 11 Moon landing was nostalgic since I saw From the editors: Scott, you’re absolutely right — we
it on TV. We’ve come a long way since then. Thank ended up saying things the wrong way around. What we
you, Astronomy magazine, for the May and July issues. should have said was, “the Milky Way will collide with
the Andromeda Galaxy in some 4.5 billion years, not
3.9 billion years, as previously thought.”

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8 ASTRONOMY • DECEMBER 2019

QG QUANTUM GRAVITYEVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH

ESA/HUBBLE & NASA, R. WADE ET AL. BOTTOM FROM LEFT: TNO/MARK CHUN; NASA; NASA/JPL-CALTECH SNAPSHOT HOT NEW TECH GALACTICA INCOGNITA ROLLING STONE
BYTES Turbulence in Earth’s From Earth, much of NASA’s InSight mission
A STAR’S atmosphere can turn the Milky Way’s far team has named a golf
DEATH crisp images of the side is obscured by ball-sized martian rock
GASPS cosmos blurry. The the crowded galactic “Rolling Stones Rock,”
University of Hawai‘i’s center. A new study of after the famous band.
This ghostly 2.2-meter telescope more than 1,000 variable The team believes
nebula previews will be first on Mauna stars in this hard-to- the rock was pushed
our Sun’s fate Kea with a bendable see region is helping about 3 feet (1 m) by the
secondary mirror to astronomers chart our spacecraft’s thrusters
The Hubble Space Telescope reduce this effect. galaxy’s structure. during landing.
has imaged the remnants of a
dying star in the constellation
Gemini the Twins several
times. Because of its unique bi-
lobed appearance, astronomers
once thought the fading system,
designated NGC 2371/2, was
two distinct objects. This is
because the planetary nebula
— an expanding shell of gas
created when a red giant star
sheds its outer layers — has
a symmetrical structure that
made it look like two dying
suns, instead of just one.

As the outer layers expand
into space, the star’s smolder-
ing core remains behind,
energizing the surrounding
gas. NGC 2371/2 is an evolving
system, with bright knots of gas
and jets of material that change
from one observation to the
next. Eventually, though, these
changes will slow as the gas
dissipates and the cooling core
forms a white dwarf, which will
grow dimmer over time. This
is the same fate astronomers
expect to befall our own Sun,
which will evolve into a similar
cosmic masterpiece in a few bil-
lion years. — HAILEY ROSE MCLAUGHLIN,

JAKE PARKS

WWW.ASTRONOMY.COM 9

QUANTUM GRAVITY

INDIA’S FIRST LUNAR LANDER CRASHES

Meant for a soft landing, Vikram slammed into
the Moon moments after going silent.

Simpelius A Manzinus E
Simpelius M Manzinus D

Manzinus C Manzinus G

Manzinus N

Simpelius N

Simpelius G

GROUND ZERO. India’s Vikram lander was

slated to touch down on a highland plain at
the lunar south pole, near the Manzinus C
and Simpelius N craters (yellow dot).
Communications cut off between the craft
and its controllers shortly before its
scheduled landing. NASA/GSFC/ARIZONA STATE UNIVERSITY

On September 6, controllers faster and harder than expected, withstand. There had been no signal
at the Indian Space Research possibly bringing its part in the from Vikram.
Organisation’s (ISRO) facility in Chandrayaan-2 mission to an end.
Bengaluru, India, watched tensely as Although the Vikram lander and
the Vikram lander approached the On September 9, ISRO reported in a its contents remain silent, the pair
Moon’s surface. The nearly 3,260- tweet that the lander had been spotted constitutes only a small part of the larger
pound (1,477 kilograms) lander was by the Chandrayaan-2 orbiter, but com- Chandrayaan-2 mission, whose orbiter
about to accomplish India’s first soft munication could not be established. will continue to study the south polar
landing on the Moon, touching down According to ISRO officials, the lander region of the Moon and will remain
closer to the lunar south pole than any was seen near the targeted landing site, operational for seven years, according
other country. apparently in one piece, albeit tilted. to an ISRO statement.
But at an altitude of about 1.3 miles The extent of the damage to the lander
(2.1 kilometers), as the craft neared and its 57-pound (26 kg) Pragyan rover, “Space is hard,” NASA tweeted to the
the end of its automated soft-landing stored inside, were not known. Indian space agency September 7. “We
sequence, communications went out. commend @ISRO’s attempt to land their
The lander could not be raised, leading ISRO attempted for 14 days to #Chandrayaan2 mission on the Moon’s
mission controllers to believe Vikram establish contact with the lander. But South Pole. You have inspired us with
had slammed into the lunar surface on September 20, Vikram’s landing site your journey and look forward to future
passed into the cold, dark lunar night, opportunities to explore our solar system
which the lander was not designed to together.” —ALISON KLESMAN, H.R.M.

10 ASTRONOMY • DECEMBER 2019

ESA/DLR/FU BERLIN QUICK
TAKES
The windswept craters of Mars
PLANET HUNTER
The European Space Agency’s Mars Express spacecraft recently revealed the bleak yet
beautiful terrain of Terra Cimmeria in Mars’ southern highlands. The stunning new views NASA’s TESS telescope completed
highlight valleys carved by liquid water that once flowed across the surface, windswept its first year of scanning the
dunes composed of sand and dust, and impact craters that run the gamut in size. Terra
Cimmeria is a particularly interesting region largely due to Eridania, a paleolake from Mars’ southern sky for exoplanets in July,
distant past, when liquid water was abundant in the southern highlands. Though the water and has since moved on to the
is now gone, its valleys and shorelines remain, as well as plenty of sediment rich in various northern sky.
clay minerals. — ERICA NAONE, J.P.
ERODING RODENTS
A COSMIC CLOCK
An international study found that
GLITCHES mice living in microgravity on the
International Space Station lost
Pulsars, the rapidly spinning cores of gas and dust left over from when X-RAY: NASA/CXC/UNIV. OF TORONTO/M. DURANT ET AL.; OPTICAL: DSS/DAVIDE DE MARTIN bone mass in their legs, while mice
of dead stars, are some of the its star went supernova more than living in hypergravity (thanks to a
universe’s most reliable rotators 10,000 years ago. Vela’s most recent centrifuge) on Earth gained both
— until they’re not. Astronomers glitch, observed in 2016, revealed a
occasionally observe “glitches” in surprise: The pulsar slowed down bone and muscle mass.
about 5 percent of pulsars, during briefly just before the faster rotation
which they speed up and briefly of the glitch kicked in. Astronomers CASTAWAY
rotate faster. They believe glitches are now on the lookout for such
occur when an inner layer of the slow-down periods preceding The crash landing of Israel’s
star suddenly sloshes outward. glitches to learn more about why Beresheet Moon probe likely left
When that layer hits the pulsar’s and how glitches happen in Vela thousands of survivors stranded on
outer crust, it causes the star to and other pulsars. — KOREY HAYNES, A.K. the Moon — specifically, tiny, hardy
spin faster before reverting to its creatures called tardigrades, which
previous spin rate within seconds. were part of an experiment the
The Vela Pulsar, which lies
1,000 light-years away, glitches as lander carried.
often as once every three years.
This composite image, which com- POSTMORTEM
bines optical and X-ray light, shows
the pulsar lurking inside the cloud University of Warwick-led
researchers have calculated that

the cores of dead planets can
survive 100 million to 1 billion years
after their stars have ballooned into

red giants, possibly providing a
glimpse into Earth’s future.

MARTIAN SCOUT

NASA’s unnamed Mars 2020 rover
will be equipped with the first

rotorcraft to fly on another planet.
However, the proof-of-concept
helicopter will not carry any
scientific instruments.

TOTAL ANNIHILATION

Astronomers have witnessed the
complete destruction of a star

that began life at some 200 solar
masses. The explosion, which
left no trace of its progenitor,
challenges theories about how
such massive stars die.

DEEP DIVE

The SETI Institute plans to
robotically explore Earth’s deep-sea

vents to practice hunting alien
life on worlds like Europa
and Enceladus. — J.P.

WWW.ASTRONOMY.COM 11

QUANTUM GRAVITY

Three Earth-sized exoplanets
discovered nearby

NEW NEIGHBORS. Three newly discovered There’s a triplet of Earth-sized instrument on the La Silla Observatory’s
exoplanetary candidates orbiting 3.6-meter telescope in Chile. Observations
planets make their home around a nearby star a star just 12 light-years away, according showed the signatures of three planetary
called GJ 1061, a cool red dwarf similar to the to a new study by a team from the Red candidates, with a possible fourth.
stars TRAPPIST-1 and Proxima Centauri. This Dots campaign, which looks for rocky, However, the scientists suspect the fourth
artist’s concept imagines a view from the Earth-like planets around nearby stars. candidate is actually stellar activity, such
surface of one of TRAPPIST-1’s multiple All three planets are about 1.4 to 1.8 as a starspot.
planets. M. KORNMESSER/ESO times the mass of Earth and orbit their
star every three to 13 days. The longest-period planet, dubbed d,
The research was published August 13 is most interesting to scientists, as it falls
on the preprint site arXiv.org, and has within the star’s habitable zone, where
been submitted to the Monthly Notices liquid water could exist on the surface.
of the Royal Astronomical Society. The But M-dwarf stars, which live longer
planets orbit GJ 1061, a low-mass, than stars like the Sun, typically are more
M-dwarf star that’s one of the 25 closest active in their early years. This means that
stars to the Sun. The star is similar to the a close-in planet like planet d may have
Sun’s nearest neighbor, Proxima Centauri, spent millions of years being blasted by
whose own planet was discovered in 2016. intense radiation, so it may not retain a
The new planets were spotted with the life-sustaining atmosphere. Nonetheless,
radial-velocity method, which measures GJ 1061 shows less violent activity than
tiny wobbles in a star’s orbit to reveal the Proxima Centauri, suggesting it might
presence of exoplanets tugging on their provide a safer environment for life.
sun. This technique typically uncovers
giant exoplanets close to their host star, “It doesn’t surprise me,” says Michael
but increasingly is used in long-term Endl at the University of Texas at Austin,
campaigns to reveal smaller planets as who was not involved with the new
well. Data were collected using the High research. “Since NASA’s Kepler mission,
Accuracy Radial velocity Planet Searcher we basically know that small planets are
abundant around those very cool and
small stars.” — MARA JOHNSON-GROH, J.P.

VENUS AT 30° 23 March 9 24 April 8
ITS BEST Feb. 8
23

25° 24

EVENING STAR. How dazzling is Altitude

ASTRONOMY: ROEN KELLY
20° Jan. 9 FAST FACT May 8

Venus? Even on a bad day, it Although Venus stands highest
shines nine times brighter than 15° 25 in the west at greatest

the night sky’s brightest star, 10° Dec. 10 elongation, it shines brightest 23
Sirius. But Venus stands out 5° 25 (magnitude –4.7) in late April.
even more when it appears far
above the horizon. Conditions 0° Nov. 10
late this winter and early spring Southwest
Azimuth West

will be ideal for Northern Hemisphere observers. This chart plots the planet’s positions for an observer

at 40° north latitude an hour after sunset. Although Venus reaches its peak altitude — 32.4° — at greatest

elongation March 24, it remains above 30° for nearly two months. — RICHARD TALCOTT

12 ASTRONOMY • DECEMBER 2019

Jupiter’s new portrait NASA, ESA, A. SIMON (GODDARD SPACE FLIGHT CENTER), AND M.H. WONG (UNIVERSITY OF CALIFORNIA, BERKELEY)

The Hubble Space Telescope’s newest image of
Jupiter, taken June 27 as part of the Outer Planet
Atmospheres Legacy program, highlights the solar
system’s largest planet in stunning color. Readily
visible is the planet’s Great Red Spot, a swirling
storm roughly the size of Earth, which has been
visible on the giant planet for at least 150 years.
Repeated observations have shown that the
tempest is shrinking slowly over time. Hubble’s
snapshot also shows other storms, including a
thin, brown, snakelike cyclone and two white oval-
shaped storms below the Great Red Spot. Driven
by high winds, Jupiter’s colorful bands of clouds
give the planet its distinct striped appearance.
These bands consist of ammonia clouds at varying
heights and thicknesses, which appear lighter or
darker depending on their properties. This latest
portrait will help astronomers better characterize
conditions on Jupiter, while also providing clues
about the environment on giant planets around
other stars. — A.K.

WWW.ASTRONOMY.COM 13

QUANTUM GRAVITY

Jupiter’s fuzzy core
hints at past collision

NASA/JPL-CALTECH

NASA’s Juno spacecraft arrived at Jupiter BANGED UP. A GALAXY
in 2016 with the goal of peering through
the giant planet’s dense clouds to reveal its A massive planet HIDES ITS
inner secrets. One of the mission’s biggest slamming into
surprises so far is that Jupiter’s core is less Jupiter during its SECRETS
compact than scientists expected. Instead infancy could have
of a sharp transition between a dense core created the ill- Galaxies come in many
of rock and ice and its more gaseous enve- defined core that shapes, sizes, and orienta-
lope, Juno’s readings imply a fuzzy bound- astronomers tions in space. Some appear
ary, with a less dense core that extends out observe in the gas face-on, while others are
to nearly half the planet’s radius. giant today. K. SUDA & tilted. From our viewpoint
on Earth, NGC 5866 is per-
Now, astronomers led by Shang-Fei Y. AKIMOTO/MABUCHI DESIGN fectly edge-on, appearing
Liu from Sun Yat-sen University in Zhuhai, OFFICE/ASTROBIOLOGY as a thin line in this image
China, have put forward an explanation CENTER, JAPAN taken by the Spitzer Space
for that fuzzy core: When forming, Jupiter Telescope. Spitzer views
suffered a head-on collision with a proto- started to develop. But this is physically objects in infrared light —
planet roughly the size of Uranus. Their unlikely. Once Jupiter started gaining an here, blue colors represent
findings were published August 14 in the atmosphere, it should have done so quickly, light at 3.6 microns,
journal Nature. and that very atmosphere would have produced largely by stars,
repelled heavier dust grains from settling which make up most of the
Leading theories state that during the onto the planet. galaxy’s bulk. Green and
planet’s formation, Jupiter collected heavy red colors correspond to
elements first, creating a compact core. At So, Liu’s team began considering how light at 4.5 and 8 microns,
that point, it was heavy enough to attract else Jupiter’s blurred core might have respectively, the latter of
huge amounts of lighter elements like formed, and after running numerous which is associated with a
hydrogen and helium, which make up most computer simulations, concluded that a flat ring, or disk, of dust.
of the planet’s bulk. collision fits the bill — specifically, a colli- Because of the galaxy’s tilt,
sion in which a massive protoplanet made it’s challenging for astrono-
That scenario would result in a distinct of dense material was perturbed from its mers to get a good look at
core; for a blurry core to occur naturally, orbit by the growing gas giant and crashed its structure. But they can
scientists say that some 10 to 20 Earth head-on into Jupiter’s core about 4.5 billion tell from the clean, straight
masses of dense material would have had years ago. shape of the galaxy’s dust
to glom onto Jupiter after its core finished that it likely has not under-
forming and its gas envelope had already “It sounded very unlikely to me, like a gone interactions with
one-in-a-trillion probability,” said Andrea other galaxies, which would
Isella of Rice University, a co-author on the warp that shape away from
paper, in a press release. “But Shang-Fei a straight line. For now, it
convinced me, by sheer calculation, that appears NGC 5866 has had
this was not so improbable.” no disruptions, though that
may change, given enough
“The only scenario that resulted in a time. — A.K.
core-density profile similar to what Juno
measures today is a head-on impact with
a planetary embryo about 10 times more
massive than Earth,” Liu said.

While there’s no way to run the clock
backward to find out for certain what hap-
pened, the theory holds for now, making it
an intriguing explanation for Jupiter’s hazy
heart. — K.H., J.P.

14 ASTRONOMY • DECEMBER 2019

WATCH FOR FAST FACT 'HGLFDWHG WR
ORBITING DEBRIS
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3,500 satellites ASTRONOMY: ROEN KELLY ZZZ DVWUR SK\VLFV FRP
0DFKHVQH\ 3DUN ,/ 86$
currently not functioning 3K
in Earth orbit
2020 TOTAL
900,000 objects SOLAR ECLIPSE TOURS

0.4–4 in 128,000,000 objects – Chile Solar Eclipse Tour
(1–10 cm) (Dec 9 -16, 2020)
0.04–0.4 in
(1 mm–1 cm) – Chile & Easter Island Eclipse
(Dec 3 -15, 2020)
NO TRASH PICKUP. Since the start of the space age in 1957, humans
have placed nearly 9,000 satellites in Earth orbit as of January 2019. Of – Brazil & Argentina Eclipse
these, more than 5,000 are still in orbit and 1,950 are still functioning. (Dec 6 -18, 2020)
The rest are considered space debris — inert artificial objects orbiting
our planet — and pose a risk for collisions with functioning satellites or – Argentina Eclipse
even crewed spacecraft. Based on these numbers and estimates for the (Dec 9 - 18, 2020)
number of events resulting in fragmentation of orbiting objects over time,
the European Space Agency estimates there are nearly 130 million pieces – Argentina & Chile Eclipse
of debris larger than 0.04 inch (1 mm) in orbit today. —A.K. (Dec 9 - 20, 2020)

600 million 2021 TOTAL
SOLAR ECLIPSE TOURS
The number of years earlier than previously
– Luxury Antarctica Eclipse
believed that Earth began experiencing plate Cruise (Nov 29-Dec 15, 2021)

tectonics, based on analysis of a drop – Private Jet Antarctica Eclipse
Expedition
of ancient seawater.
Eclipse Traveler

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WWW.ASTRONOMY.COM 15

STRANGE UNIVERSE

Two-dog night thick horizon air, the result is often a kaleidoscope of
rapidly changing color. I’ve received a half-dozen UFO

Our canine constellations have faithful companions calls over the years that proved to be the madly mutat-
ing Dog Star. Its mongrel maelstrom of color is the

of their own. result of its spectral A-type light refracted by prismlike

air layers, transmitting alternating parts of its vivid

glow. Sirius is a great target for a spectroscope.

Of course, viewing Sirius means seeing the combined

light of two famous stars. Circling each other every

50 years in a wildly eccentric orbit, they are finally far

apart. Now and for the next few years, you can glimpse

the dim Pup a comfortable 10" from the blazing pri-

mary, especially if you nudge the scope to keep Sirius

A’s insane dazzle out of the field.

Sirius B is a sphere only about the size of Earth, yet

its mass some 350,000 times greater means it has col-

lapsed to an interesting degree. On Earth, the densest

materials are about 20 times heavier than water. But

Sirius B is about 130,000 times denser than water.

Imagine landing on its diamond-hard surface. Even

if you could shield yourself from the heat, its merciless

gravity would freeze all your motion like a frame in a

jammed projector. Your lungs could not take one breath,

nor your muscles lift a single finger to warn others. Yet

Sirius A, the Dog Star We’ve gotten so spoiled when it comes to these fantastic stars are common. Of the 58 suns lying
(center), has a smaller strangeness that white dwarfs no longer drop within about 16 light-years of Earth, five are white dwarfs.
“pup” companion. The Sirius B takes honors as the nearest. But twice its dis-
white dwarf Sirius B

peeks out from the our jaws. Since neutron stars and black holes tance, at 16 light-years — also optimally seen this month
light of its larger are much more mind-bendingly squashed, we disregard — lies the easiest white dwarf to spot, and my favorite.
companion in the the runners-up in the crushed-fireball sweepstakes. It’s Simply follow the starry line that heads right from Rigel
lower left-hand region like ignoring a pterodactyl in your garden just because to form Eridanus the River, and you’ll quickly reach two
of this Hubble Space your girlfriend admitted she’s an alien six-dimensional matching 4th-magnitude stars. Point your trusty scope
Telescope image. J-creature.
at the bottom one. Call it 40 Eridani. Or
NASA, ESA, H. BOND (STSCI), AND

M. BARSTOW (UNIVERSITY OF

LEICESTER) Well, white dwarfs still twist my head — Omicron2 (ο2) Eridani. Or Keid. A mere 50x

especially now, when the half-century wait- Of the 58 shows the main star has a distant double-star
ing period is over and we can finally see the suns lying companion, discovered by William Herschel
most famous one. I’m talking about the Pup, two years after he found Uranus. This com-
companion to the Dog Star, Sirius. within panion pair is an easy binary separated by 8".
about 16 The brighter of these two is the white dwarf,
That alpha star of the Big Dog constella-

tion was considered bad news for a thousand light-years the first ever recognized.

years. In the Roman Empire, its presence was of Earth, And call the pound: This same patch of
so ill-omened that hit men were sometimes five are December sky has yet another dog running
employed to sacrifice dogs after Sirius rose. white loose. Between Sirius and Keid we have
Even Dante wrote of the star as “the scourge dwarfs. Procyon, sitting just 11.4 light-years away.
of days canicular.” Can it be that the brightest star of the Little

The Dog Star had better press in ancient Dog has a white dwarf companion rivaling

Egypt, where they believed July’s sky- the Big Dog’s? And that both systems have

proximity between the Sun and the brightest star orbital eccentricities of about 0.4? With both orbiting

BY BOB BERMAN caused the summer’s heat. Even today we use the at a separation of around 20 astronomical units, match-

Join me and Pulse expression “dog days” to mean sultry weather, most ing the Sun-Uranus separation?
of the Planet’s people unaware that its origins echo from those van- Yes, it’s true: All our Dog Stars have dense little pups.
Jim Metzner ished centuries.
in my podcast, It’s weird, but also kind of cute.
Astounding Universe, In real life, December’s dinnertime rising of Sirius
at www.astounding provides not warmth but a psychedelic light show. BROWSE THE “STRANGE UNIVERSE” ARCHIVE
universe.com When that dazzling starpoint shines through cold, AT www.Astronomy.com/Berman

16 ASTRONOMY • DECEMBER 2019

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P29014 WWW.ASTRONOMY.COM 17

SECRET SKY

Thoughts on a partial
lunar eclipse

A lot more was going on than you’d think.

1

2

observing behavior: During penumbral ingress, I

focused my attention only on the section of the Moon

that was to receive the shadow — just as one would

while awaiting the first nibble out of a solar eclipse.

During egress, however, my eye did not stop comparing

the shadowed region with the opposing bright lunar

limb — so I was continually evaluating the shifting

relative brightness of the two regions. Image 2 shows

how the penumbral shading was apparent in images

1. This artistic through my 3-inch refractor 50 percent into the pen-
composite image
shows the main On the night of July 16/17, 2019, I watched umbral phase, and other images show it earlier still.
phases of the
July 16/17, 2019, partial — for the first time in decades — a partial
lunar eclipse (running
right to left). Here, lunar eclipse through an 8-inch telescope. Umbral irregularities
they are being
“uplifted” by yoga Usually, I have monitored the visual phenomenon with For the first five minutes after Earth’s umbral shadow
students on the
Makgadikgadi Pans either my naked eyes or binoculars. But the change cast slipped onto the lunar disk, it appeared as a small semi-
in Botswana, Africa.
some new light onto my impressions of Earth’s shadow. circular dark path surrounded by a dark gray aureole. Five
ALL PHOTOS: STEPHEN JAMES
O’MEARA Penumbral differences minutes later, the central dark patch and aureole reversed
intensities, with the core appearing brighter
2. Three high-contrast
images show the I was particularly surprised by how difficult than its surrounding ring. Another five min-
subtle effects of the
penumbra. South it was to perceive Earth’s penumbra (its The reverse- utes into the event, and the entire umbral
is up. lighter outer shadow) during the early stages Life Saver shadow was a uniform dark gray surrounded
of this 65-percent partial eclipse. The bril- effect was by an equally uniform collar of lighter gray.
BY STEPHEN liance of the Full Moon is formidable a mystery. The reverse-Life Saver effect was a mystery,
JAMES O’MEARA through an 8-inch telescope without a filter. though I believe it to be a contrast effect
Stephen is a globe-
trotting observer who And although I knew some penumbral between the bright highlands and the dark
is always looking
for the next great phases of partial eclipses go unseen, the maria as the shadow moved over the region.
celestial event.
shadow’s smoky yellow presence made itself obvious What was most apparent as the eclipse deepened was

only about 25 minutes prior to the appearance of Earth’s that the leading edge of the umbra appeared bluer than

umbra (its darker inner shadow), or about 70 percent the deeper reddish umbral section. This is typical of an

into the penumbral phase. eclipse where the Danjon value (a scale that evaluates

While this is within the norm, I found the situation the color of total lunar eclipses) equals 4, which occurs

during the shadow’s egress different. Namely, I found when Earth’s atmosphere is clear of contaminants (such

it much easier to follow the penumbra’s departure as volcanic aerosols). The blue collar, as shown in

almost to the Moon’s edge. My guess is that it is easier Image 3, is caused by light passing through the clear

to follow something dark becoming lighter (because upper stratosphere and penetrating the ozone layer,

your eye and brain can gradually accustom to the which absorbs red light, thus making that section of the

brightening shadow) than something overpoweringly shadow appear bluer. Close inspection also revealed the

bright becoming partially dimmed. deepest penumbral shadow causing a yellow band to

However, I also noticed something different in my appear beyond the blue one.

18 ASTRONOMY • DECEMBER 2019

3

4 5 3. The blue leading
edge of Earth’s
There was also something else at play, which made of the maria), as you can see in Image 5 taken through shadow is rimmed by
it difficult to judge the overall intensity of the shadow’s a 3-inch telescope at prime focus. Through the 8-inch, a smoky yellow deep
color. In Image 3, note how the southern highlands however, the shadow’s edge remained smooth through- penumbral shadow.
(at the top) appear so much brighter than the remain- out the eclipse, as it should.
der of the disk in shadow. This is not due to irregulari- 4. As the eclipse
ties in Earth’s atmosphere, but rather due to albedo Send your thoughts on any lunar eclipse to progressed, the edge
effect. Lunar highlands reflect twice as much light as [email protected]. of Earth’s umbral
the darker maria, which dominate the shadowed shadow appeared
region. BROWSE THE “SECRET SKY” ARCHIVE AT irregular as it covered
www.Astronomy.com/OMeara the maria — to the
This same phenomenon caused the first half of the unaided eye and
umbral eclipse to appear darker than the second half. through binoculars.
As Image 4 shows, the reason for the intensity differ-
ence is largely due to the greater amount of highland 5. Two exposures of
material appearing in the deeper (redder) part of the the same length show
shadow during the second half of the eclipse. albedo differences in
Earth’s shadow. The
One other aspect of the eclipse surprised me. To my darker maria in the
naked eyes and through binoculars, the edge of the exposure dominate
Moon’s shadow appeared irregular (a contrast illusion the view in the deep
created as the shadow covers the irregular boundaries shadow during
ingress (left). Highly
reflective highland
material dominates
the deep shadow
during egress (right).

WWW.ASTRONOMY.COM 19



THE EXPLORATION OF worth it, though: When New Horizons’
PLUTO WASN’T EASY, BUT data arrived on Earth, it revealed vast
IT SURE WAS WORTH IT. As nitrogen glaciers, methane- and water-
ice mountains, a complex atmosphere,
David Grinspoon and I recount in our and a range of terrain ages that prove
book, Chasing New Horizons, it took the planet is intensely active more than
14 years (1989 to 2003), about a dozen 4 billion years after its formation. But
different mission concept proposals, there was more — including evidence
and the weight of the first National for organic compounds, liquids on
Academy Planetary Science Decadal Pluto’s surface in its past, ice volcanoes
Survey just to unleash the funding. that erupted onto the planet’s surface,
After a fierce competition among rival and an ocean of liquid water in Pluto’s
teams, NASA ultimately selected New interior.
Horizons as its Pluto flyby mission.
Pluto’s moons didn’t disappoint,
That was followed by a breakneck either. New Horizons found new evi-
four-year schedule to design, build, and dence that they formed together after an
test the spacecraft in order to meet the ancient, giant impact between Pluto and
time-critical 2006 launch window another dwarf planet. Pluto’s largest
needed to use Jupiter for a gravity assist. moon, Charon, also revealed a puz-
Once that was achieved, New Horizons zlingly reflective surface and never-
had to undertake the 9.5-year journey before-seen dark polar caps seemingly
across our solar system to reach Pluto made of methane that had escaped from
and its system of five moons. The entire Pluto’s atmosphere.
effort took 26 years and the dedication
of literally thousands of individuals, and Those are just a few of the discover-
was done entirely with no backup, no ies that New Horizons made. And I can
plan B, no Voyager 2 in case Voyager 1 tell you, now four years after that flyby,
failed. the New Horizons science team and
many other members of the planetary
SPECTACULAR RESULTS science community have concluded that
a new mission to explore Pluto in more
In a real sense, I think the solar system depth is required to unravel these
saved the best for last. The wait was puzzles.

A proposed Pluto orbiter, seen here flying above the This is needed in part because much
canyon system that dominates the planet’s large of Pluto and its moons couldn’t be
moon, Charon, could explore the Pluto system for mapped in sufficient detail with a single
at least two years. RON MILLER FOR ASTRONOMY

WWW.ASTRONOMY.COM 21

Pluto is a dynamic world, with a roiling

nitrogen glacier, avalanches, and a com-

plex and time-variable atmosphere. But

New Horizons’ flyby reconnaissance of

Pluto all took place in one roughly

24-hour period, July 14, 2015. It gave us

a wonderful snapshot first look, but no

chance to see the daily, seasonal, and

geological changes that an orbiter can

probe but a flyby cannot.

Third, we learned that new kinds of

instrumentation will be needed to

answer the many questions that the New

Horizons data sets raised. Going back

with an orbiter will allow us to use

instruments to peer through Pluto’s gla-

ciers with radar to determine how deep

they are. The spacecraft also will carry

Just 15 minutes after its closest approach to Pluto, NASA’s New Horizons spacecraft looked back toward the a mass spectrometer to sample Pluto’s
planet and captured this near-sunset view of its rugged, icy mountains and flat ice plains. The smooth atmosphere, inventory all the com-
expanse of Sputnik Planitia (right) is flanked to the west (left) by rugged mountains up to 11,000 feet pounds there, and determine the nature
(3,500 m) high. ALL IMAGES BY NASA/JHUAPL/SWRI UNLESS OTHERWISE NOTED

of Pluto’s hazes.

And there is so much more. Only by

radio tracking a vehicle, orbit after orbit,

can we probe the interior of Pluto to

determine if the suspected ocean is really

there. And we need to send a thermal

mapper to determine how Pluto’s vast

glaciers are powered and if its ancient ice

volcanoes are still active. Without flying

a magnetometer, we will never know if

the planet’s core is alive and churning or

dead and frozen solid. Finally, we want to

send lidars and other active instruments

that can make maps even in the darkness

of polar shadows. The aim is to inspect

the night sides of Pluto and its moons to

detect changes as the temperatures plum-

When New Horizons was 11,000 miles (18,000 km) past Pluto, it took this wide-angle image that shows met when the Sun goes down.
the deep haze layers of the planet’s atmosphere. The left and upper parts of the disk are dark because So, we need an orbiter to complete
Pluto is casting its shadow on its atmosphere. The backlighting highlights more than a dozen layers of
haze. The horizontal streaks in the sky beyond Pluto are stars, smeared out by the motion of the camera the job that New Horizons started so
as it tracked Pluto. well. That orbiter should be designed to

operate for years, not days, returning

fast flyby. It’s also needed because Pluto’s MORE GOALS FOR A data week in and week out as it closely

surface and atmosphere are evolving RETURN TO PLUTO inspects all of Pluto’s moons and watches

with time and beg for an orbiter to Why do we want to go back? There the planet’s surface and atmosphere

observe those processes. But the main are many reasons. First, limited by the evolve.

reason for a new mission is that many nature of its fast flyby, New Horizons

of the mysteries New Horizons found could map only 40 percent of Pluto’s DESIGNING THE MISSION

require new types of instrumentation to geology and surface composition at good With all this in mind, I led an internal

be brought to bear — instruments New resolution. The same is true for Charon. research project from mid-2017 to mid-

Horizons did not carry. And we learned even less about 2019 at the Southwest Research

Whether that orbiter mission is Pluto’s four small moons Institute (SwRI) to study

funded depends almost entirely on the because the craft didn’t We need an how to implement
findings of the next planetary decadal fly close to any of a Pluto orbiter.

survey, whose committee will begin its them. orbiter to complete The study team
work next year. The survey results will Second, we the job that New Horizons included
appear in 2022. my SwRI
learned that started so well.

22 ASTRONOMY • DECEMBER 2019

The New Horizons
spacecraft, which had
its closest encounter
with Pluto on July 14,
2015, revealed the
planet in spectacular
detail.

CHARON AND THE SMALL MOONS OF PLUTO

This composite image shows part of Pluto’s Styx Nix Hydra
largest moon, Charon, and all four small Kerberos Charon
moons, as resolved by the Long Range 10 miles
Reconnaissance Imager on the New Horizons
spacecraft. Charon has a diameter of 751 miles
(1,212 km). Nix and Hydra have comparable
sizes, approximately 25 miles (40 km) across
in their longest dimension. Kerberos and Styx
are much smaller and have comparable sizes,
roughly 6 to 7 miles (10 to 12 km) across in
their longest dimension.

10 km

This enhanced color mosaic combines some of the
sharpest views of Pluto captured by New Horizons.
They are part of a sequence taken near closest
approach and have resolutions of about 250 to
280 feet (77 to 85 m) per pixel, which reveal surface
features smaller than half a city block. Scientists
then added lower resolution color data. The images
form a strip 50 miles (80 km) wide, trending from
the northwest of Sputnik Planitia, across the Al-Idrisi
Mountains, onto the shoreline of Pluto’s “heart”
feature, and just into its icy plains.

assists. When we simulated the idea, it
worked beautifully, eliminating most of
the fuel an orbiter needs to carry.

THE TIMELINE

The mission timeline we created is as

follows: Launch in December 2028, a

This enhanced color view shows the southeastern portion of Pluto’s great ice plains. At lower right the plains Jupiter gravity-assist flyby in October
border rugged, dark highlands named Krun Macula. (Krun is the lord of the underworld in the Mandaean 2030, braking into Pluto orbit begin-
religion, and a macula is a dark feature on a planetary surface.) Researchers think the dark red color comes ning in 2046, and concluding in 2059.
from tholins, complex molecules found across Pluto. We could get there faster if high-power

nuclear systems are available to increase

colleagues Tiffany Finley, Mark Tapley, Pluto orbiter to follow up on the discov- braking thrust so the orbiter has enough

John Scherrer, and Amanda Zangari eries of New Horizons. power to slow down at Pluto, but a

(who is now at Lincoln Labs). One of the top breakthroughs was a slower trajectory is feasible with current

The mission design we created put game-changing solution to the propul- systems.

a New Horizons-scale spacecraft with sion requirements to tour the Pluto sys- The resulting two-year tour of the

new instruments into Pluto orbit. It tem, which originally added a huge Pluto system begins with a Charon grav-

requires one of the massive new, Saturn amount of mass to the spacecraft. We ity assist and a braking maneuver to

V-class launch vehicles now in develop- discovered that virtually all of the pro- complete the Pluto orbit injection. Then,

ment, a Jupiter gravity assist, and a pulsive needs to explore many aspects using orbits that are typically just a cou-

nuclear electric stage augmented by a of the planet and its satellites could be ple of weeks long, the craft will explore

chemical propulsion braking stage to eliminated using targeted close flybys of each of Pluto’s small moons half a dozen

reach Pluto orbit. Pluto’s Texas-sized moon Charon times in close flybys — and

We studied what kind of payload for repeated gravity assists. Charon itself with more

should be flown on such an orbiter, what This is analogous to The tour than 30 close flybys. It
kind of orbital tour would be possible, how the Cassini could continue also will make both
what the main orbiter spacecraft attri- orbiter toured the polar and equato-

butes need to be, and how to get such a Saturn system much longer, but after rial flybys of
spacecraft from Earth to Pluto. This using the large two years, the spacecraft will Pluto and dip
study constituted the first, and presently moon Titan have met all of the scientific into Pluto’s
the only, investigation of how to build a for gravity upper

objectives we set for it.

24 ASTRONOMY • DECEMBER 2019

atmosphere for sampling multiple times. completely untenable for an orbiter, The telescopic camera
And it will fly over Pluto’s poles many which needs to send its data to Earth on the New Horizons
times, as well as out into its distant every 15 to 30 days to be effective. That spacecraft took this
“magnetospheric tail” for specialized in turn requires a much larger dish high-resolution image
studies. The tour could continue much antenna and a transmitter nearly 10 of an intricate pattern
longer, but after two years, the spacecraft times more powerful, along with smarter of pits. Scientists
will have met all of the scientific objec- software to remove background noise believe these
tives we set for it. from images and spectra. Fortunately, indentations form
none of these changes requires new tech- through a combination
THE SPACECRAFT nology, and the mission looks entirely of ice fracturing and
feasible with existing flight systems. evaporation. The
Most of the capabilities needed for the scarcity of impact
orbiter spacecraft are similar to those for GO WIDE OR GO DEEP? craters in this area may
New Horizons. But the resulting flight mean that these pits
system, which features twice the payload Before the exploration of the Pluto sys- formed relatively
mass of New Horizons, fully redun- tem in 2015, most planetary scientists recently. By studying
dant spacecraft systems, and electric thought the natural follow-up to New them, researchers hope
and chemical propulsion systems, has a Horizons would be the flyby recon- to learn about the ice
mass of 5,156 pounds (2,339 kilograms). naissance of other dwarf planets in the flow and the exchange
That’s the current estimate. However, Kuiper Belt. This way, the diversity of of nitrogen and other
the launch vehicle we chose will be able dwarf planets could be explored in the volatile materials
to lift 30 percent more than that into between the surface
space, in case the payload changes. That and the atmosphere.
weight is nearly five times more than
New Horizons, but that’s the nature of an same way that the Mariner, Pioneer, and
orbiter mission because it must carry so Voyager missions conducted the first
much fuel to brake into Pluto orbit. reconnaissance of all the terrestrial and
giant planets decades ago.
There are three primary differences
between the proposed orbiter and New However, the spectacular complexity
Horizons. The first is the need for either found in the Pluto system created con-
more onboard fuel or spacecraft reaction tention in the Kuiper Belt, dwarf planet,
wheels to perform the thousands of and planetary origins communities.
pointing maneuvers during the two-year Many, myself included, argued that we
tour. The second is the need for larger needed instead to return to Pluto to
onboard data storage than the 16 giga- study it in depth via an orbiter mission,
bytes that New Horizons carried. But the rather than reconnoitering the diversity
biggest single change is the need for a of Kuiper Belt dwarf planets with new
more capable communications system. flyby missions to several of them.

The communications system built to But, in our second breakthrough, the
return all the data from the single flyby Pluto orbiter study that I led at SwRI also
that New Horizons performed took showed that it is possible to have both
16 months to complete its job. That’s — i.e., to combine the two missions into
one, and to do so at an affordable cost.
Because that breaks the tug of war

WWW.ASTRONOMY.COM 25

Pluto’s north polar
area shows a diversity
of geological and
compositional features
in enhanced color. Long
canyons — the largest is
about 45 miles (75 km)
wide — run vertically
across this region.
Roughly parallel
subsidiary canyons to
the east and west are
approximately 6 miles
(10 km) wide. The
degraded walls of these
canyons appear much
older than the more
sharply defined canyon
systems elsewhere on
Pluto, perhaps because
they are made of
weaker material.

between going wide in studying other
dwarf planets and going deep in Pluto
studies, we dubbed the resultant all-in-
one concept the “Gold Standard” Pluto-
Kuiper Belt exploration mission.

This is the highest-resolution color shot of Pluto’s receding crescent, taken when New Horizons was THE GOLD STANDARD
120,000 miles (200,000 km) past the planet. The image is dominated by atmospheric layers of blue haze,
which scientists believe is a photochemical smog. It may form when sunlight interacts with methane and The game-changing Gold Standard mis-
other molecules, producing a mixture of hydrocarbons. These, in turn, accumulate into small haze particles sion works like this: First, after an orbital
a fraction of a micrometer in size, which preferentially scatter blue light — the same process that can make tour of Pluto, a final pair of close gravity-
haze appear bluish on Earth. assist flybys of Charon will free the
orbiter from the Pluto system to explore
the Kuiper Belt without any need for
any propulsion from the orbiter. Next,
using only the existing capabilities of the
NASA Dawn mission electric propulsion
system, the craft will conduct a flyby
tour of up to a half-dozen small Kuiper
Belt objects and any one of a number of
dwarf planets. In fact, in some scenarios,

26 ASTRONOMY • DECEMBER 2019

A GEOLOGICAL WONDERLAND

The nitrogen-ice plain Sputnik Planitia and surrounding terrain feature in this geological map. All of the
terrain in this map has been imaged at a resolution of approximately 1,050 feet (320 m) per pixel or
better. The blue and green that fill the center of the map represent different textures, from cellular
terrain in the center and north to smooth, pitted plains in the south. The black lines represent
the troughs that are the boundaries of cellular regions in the ice. Purple represents the
mountain ranges that line Sputnik’s western border, and pink represents the scattered hills
at its eastern edge. The possible cryovolcano Wright Mons appears in red in the southern
corner of the map. Rugged highlands are dark brown along the western edge and
contain many large impact craters, mapped in yellow.

the Dawn propulsion system can even profound impact for a broad suite of closer to home, are too complex and
place the Pluto orbiter around a second planetary science studies including planet too compelling to be left to a single first
dwarf planet for another orbital mission. and planetesimal formation, ocean flyby reconnaissance. Pluto beckons, and
worlds, exotic atmospheres, the workings we must return with an orbiter. The Gold
These breakthroughs crush the debate of dwarf planets, and potentially even Standard can solve the tension between
about whether the next exploration step astrobiology. This proposal creates a pow- scientists wishing to return to Pluto and
after New Horizons should be to fly by erful mini-flagship mission for the next others who think it wiser to explore the
other Kuiper Belt objects and dwarf plan- planetary decadal survey to consider. broader Kuiper Belt.
ets or to instead orbit Pluto, because
we’ve shown that this debate is moot — CONCLUSIONS Planetary scientist S. Alan Stern is the
a single mission can do both. principal investigator of NASA’s New
A key finding from New Horizons is that Horizons mission to Pluto.
Such a mission could be launched in Pluto and its moons, like other planets
the late 2020s or late 2030s. It would have

This high-resolution swath of Pluto sweeps over the cratered plains at the west of the hemisphere A key
New Horizons encountered and across many prominent faults. It skims the eastern part of the dark finding from New
region known as Cthulhu Regio and passes over the possible cryovolcano Wright Mons. The pictures Horizons is that Pluto
in this mosaic were taken by the Long Range Reconnaissance Imager in “ride-along” mode with the and its moons are too
Linear Etalon Imaging Spectral Array, which accounts for the zigzag pattern. Taken shortly before complex and too compelling
closest approach to Pluto, details as small as 500 yards (457 m) can be seen. to be left to a single first flyby
reconnaissance.



Revered as a great thinker
and scientist, he was
also obsessive, secretive,
vindictive, and paranoid.

BY RAYMOND SHUBINSKI

the
oddities

of
Isaac Newton

BY JUNE 1665, THE PLAGUE WAS BURNING THROUGH ENGLAND. A young University of

Cambridge student, Isaac Newton, had left the school and returned to his family farm at Woolsthorpe
Manor in Lincolnshire after the university closed. Here, he lived for two years in near isolation and
produced the greatest creative output of his life.

LEFT: A facsimile It’s easy to think of Newton only as a lonely understand the time and place in which he
of a letter from and antisocial genius sitting at a desk, unraveling lived. King Charles I was beheaded in 1649,
Newton to Dr. the mysteries of the universe. Yet there is so when Newton was 7 years old, and Oliver
William Briggs, much more. In his lifetime, Newton vigorously Cromwell and his son ruled England with a
written June 20, conducted experiments, constructed models, firm Puritanical hand for the next 11 years.
1682, contains conceived of the theory of gravity, and built the Newton and his family were members of the
Newton’s thoughts first usable reflecting telescope. He created a new Church of England, and young Isaac was
on Briggs’ own form of mathematics, reformed the currency of well versed in church doctrine. But his beliefs
— ultimately England while Master of the Mint, and pursued changed as he grew older, ultimately putting
inaccurate — counterfeiters to their deaths on the scaffold. him in peril of dismissal from his post at the
theories on the He also studied the forbidden art of alchemy. University of Cambridge.
optic nerve and Newton was a deeply religious man, but a secret
vision. XTRASYSTOLE/ nonconformer to the Church of England. He was Born on Christmas Day 1642 (according to the
cantankerous, paranoid, and feared that his hard old Julian calendar then in use), Newton was a
WIKIMEDIA COMMONS work would be stolen by others. sickly child and not expected to live. His father
died a few months prior to Newton’s birth, and his
RIGHT: This Early life and experiments mother, Hannah, remarried three years later.
depiction of the Newton was left in the care of his maternal grand-
great thinker is Newton was a product of mid-17th century mother. Apparently, the young Isaac felt aban-
featured on England. To understand the man, we need to doned — years later, he listed as a grievous sin an
a collectible card
packaged with
cigarettes in the
1930s. RAYMOND SHUBINSKI

WWW.ASTRONOMY.COM 29

These engravings feature an older Isaac Newton; the image at left appeared
in an 1889 book, Famous Men of Science. The work at right is based on a 1725
portrait of the scientist belonging to the Royal Society. SARAH K. BOLTON; JOHN VANDERBANK

As Lucasian Professor of Mathematics at Trinity College in Cambridge,
Isaac Newton was required to give regular mathematics lectures.

Apparently, he was so bad at this that students stopped coming to class.
At times, Newton would simply speak to an empty room.

angry outburst in which he had threatened to burn the This is when he developed the bino- Woolsthorpe Manor in
house down around his mother and stepfather. mial theorem that led to calculus, Lincolnshire, England,
completed his early work on the theory was Newton’s home.
In fact, Newton made a list of 57 such “transgres- of gravity, and conducted several opti- He was born there
sions,” including making pies on Sunday, striking cal studies, including his work with and also retreated to
many people, setting his heart on money, stealing sunlight. By sending the Sun’s light the family home while
plums and sugar from his mother, punching his sister, through a slit in a window shade and the University of
gluttony, and beating Arthur Storer, the first astrono- passing the light through a prism, he Cambridge closed
mer to move to colonial America. Newton felt he was broke the beam into a rainbow, or during the plague
a great sinner. spectrum. Then, passing the light from 1665 to 1667.
through a second prism, he realized During this time, he
Newton’s mother did her best to turn her son into carried out several of
a farmer, but Newton would have none of it. He was his famous optical
allowed to attend university because, according to his experiments. DEFACTO/
mother’s brother, William Ayscough, he was not fit to
do anything else, thanks to his poor health growing WIKIMEDIA COMMONS
up and his apparent lack of interest in anything
except making models and reading books. that the prism wasn’t creating the

Newton was a vigorous experimenter, and the sto- colors, but that they were a property
ries of his work and discoveries made while isolated at
Woolsthorpe during the plague years are well known. of the Sun’s light.

Newton also used himself as a guinea pig in what

might have been a rather ill-advised attempt to better

understand color and vision. In the first half of the

17th century, the French philosopher René Descartes

had proposed a curious idea about color. He suggested

30 ASTRONOMY • DECEMBER 2019

that color perception was caused by pressure exerted wall, he saw concentric circles of light and color he LEFT: Newton’s
on the eye by swirling vortices. Newton read about called “motion of spirits.” own first edition of
this and didn’t agree. Philosophiae Naturalis
Newton vs. Hooke Principia Mathematica
Descartes had conceived of the notion as a philo- includes his
sophical construct. Newton would only accept exper- Although Newton is given credit for the theory handwritten notes
imental proof. He was curious as to how the shape of of gravity, he wasn’t working in a vacuum. Robert for changes in a
the eye affected color perception. To deform his eye- Hooke, Edmond Halley, and others were also future publication.
ball, he placed a bodkin, a kind of blunt needle, intrigued by the problem. Also note Samuel
under his eyelid. By carefully moving the bodkin, he Pepys’ name — Pepys
pushed his eye around, producing odd circles of color Hooke was one of the most brilliant scientists was president of the
and other images. in 17th-century England. He has even been called Royal Society at the
England’s Leonardo. Yet we have no contemporary time of the book’s
But not all of his experiments were quite so dan- portrait of the man — a result of Newton’s vendetta publication. ANDREW DUNN
gerous. He watched the light of the setting Sun against him.
through the fringes of a feather. This created a dif- RIGHT: The interior
fraction effect, producing bands of light and color as Hooke came from poor circumstances. He served pages of a personal
the incoming sunlight bent around the edges of each as curator of the Royal Society, a scientific fraternity, copy of Principia also
barb. In another effort to understand vision, Newton in its early years, where he was charged with caring show annotations in
stared at an image of the Sun reflected in a mirror for for the society’s growing collection of equipment and Newton’s hand.
as long as possible. When he finally looked away at a setting up the experiments for the regular meetings
of its members. His 1665 book, Micrographia, was an CAMBRIDGE UNIVERSITY LIBRARY

The famous Flower
of Kent apple tree at
Woolsthorpe Manor
sparked Newton’s
interest in gravity.
According to
Newton himself,
when he saw an
apple fall from the
tree one day, he
wondered why the
fruit fell straight
down, rather than
sideways, upward,
or in some other
fashion. FRITZBRUNO/

WIKIMEDIA COMMONS

WWW.ASTRONOMY.COM 31

On this page from Newton’s essay on color vision, “Of Colours,” he describes an experiment in which instant hit. On January 20, 1665,
he deformed the shape of his own eye using a blunt needle, to observe the effects on his sight. Samuel Pepys, clerk of the Royal Navy
and future president of the Royal
CAMBRIDGE UNIVERSITY LIBRARY Society, sat up reading his new copy
until 2 A.M. Pepys declared Hooke’s
32 ASTRONOMY • DECEMBER 2019 work “the most ingenious book that
ever I read in my life.”

But Hooke also tried to take on the
great Newton. In the early 1670s, Hooke
proposed the idea that the planets were
held in place by a force inversely propor-
tional to their distance from the Sun.
Newton apparently had the same idea as
early as 1666, but hadn’t published his
work. In the summer of 1684, Hooke,
Halley, and the English architect and
astronomer Christopher Wren discussed
the inverse square law over strong coffee
without satisfactory results. Halley went
up to Cambridge to see if Newton had
any ideas. The resulting meeting lit a fire
under Newton, culminating in the publi-
cation of Philosophiae Naturalis Principia
Mathematica in 1687.

Hooke was every bit as obstinate
as Newton. When the manuscript of
Principia made its appearance at a meet-
ing of the Royal Society on April 28,
1686, Hooke had a lot to say. After a con-
tentious meeting, the members removed
to a local coffee house. There Hooke
stated that he had discovered the inverse
square law and had hinted at this discov-
ery in a letter to Newton. Hooke wanted
credit for the idea. Halley wrote to
Newton to find out the truth. In his
reply, Newton claimed that Hooke had
stolen this idea by way of letters sent
from Newton to the Dutch scientist
Christiaan Huygens.

The war of words became increas-
ingly bitter when they argued over color
and the nature of light. Newton, how-
ever, struck the final blow. Hooke died
in 1703. Later that same year, Newton
became president of the Royal Society.
One of his first acts was having the only
portrait of Hooke destroyed. He also had
a great deal of Hooke’s archived papers
and research removed from the society.
Fortunately, much of Hooke’s work was
eventually recovered.

Newton turned on or argued with
nearly everyone in the scientific commu-
nity of the time. Most famous were his
efforts to prove his discovery of calculus.
The German mathematician Gottfried
Leibniz published his work on calculus

In part because of
Newton’s vendetta
against him, no
paintings of Robert
Hooke survive. This
painting of Hooke
(left), completed in
2004, is based on
the descriptions of
two contemporaries:
John Aubrey and
Richard Waller.
Samuel Pepys (right)
spent most of his life
on better terms with
Newton. Here, he
appears on a
collectible card sold
with cigarettes in
the late 1930s. RITA

GREER; RAYMOND SHUBINSKI

One of Newton’s most famous quotes, “If I have seen further it is by
standing on the shoulders of giants,” may, in fact, have been a jab at

Robert Hooke, who is said to have been hunchbacked and rather short.

in 1684. Newton immediately tried to prove his prece- Following his
dence and started an acrimonious debate that lasted death in 1726
for years. He also turned on Huygens, as well as the (or 1727,
first Astronomer Royal, John Flamsteed, and many depending on
others. He even accused Pepys, his friend, of speaking the calendar in
ill of him. It seems Newton could not stand to be use), Newton
upstaged or criticized by anyone, friend or foe. was buried in
Westminster
Clash with the church Abbey in
London. This
Genius is obsessive, and Newton was no exception. monument
Two of his greatest interests were religion and the sits above
dark art of alchemy. His early list of “sins” clearly his tomb.
shows the depths of his religious convictions. One
of the Church of England’s core beliefs is the doc- KLAUS-DIETER KELLER/
trine of the Holy Trinity, which describes God as WIKIMEDIA COMMONS
three separate entities. This doctrine almost spelled
disaster for Newton and his career. WWW.ASTRONOMY.COM 33

The young Newton began his studies at Trinity
College in Cambridge in 1661. To earn his keep, he
waited tables and cleaned rooms. Newton was
awarded his bachelor’s degree in 1665, and although
he briefly went home when the school closed due to
plague, he was back at Cambridge by 1667 as a newly
appointed fellow on the faculty. By 1669, Newton had
been appointed Lucasian Professor of Mathematics. To
remain in this post, he was required to take an oath
stating that he believed and accepted the Thirty-nine
Articles of the Anglican Church.

One of the articles to which Newton would need
to swear was a belief in the Holy Trinity. This repre-
sented a major stumbling block for the young profes-
sor. In his early years at Cambridge, Newton had
plunged into personal religious studies. With typical
Newtonian intensity, he studied the history of the
Christian church from its earliest days. He carefully
analyzed the prophesies in the Bible and calculated
the date of the crucifixion. He even tried to deter-
mine the date of the Apocalypse: Newton thought
this would take place in the year 2060.

What disturbed him most was the concept of the
three-in-one nature of God. Newton found the Holy
Trinity not only illogical, but abhorrent. He had read
the works of an early Christian named Arius. This
writer denied the divinity of Jesus, and Newton fully
embraced the idea. He could not, therefore, swear to
believe in the Holy Trinity when, in fact, he did not.

Newton was ready to resign his chair rather than
swear a false oath. Isaac Barrow, Newton’s mentor and
first Lucasian Professor at Cambridge, appears to have
sent letters on his behalf to King Charles II, who at the
last minute provided a dispensation for Newton. If the
truth of Newton’s beliefs had been made public, he
would have been branded a heretic and could have
been locked away in the Tower of London.

Newton the alchemist

Newton was so obsessed with religion and alchemy
that he wrote far more words on them than he ever
did about gravity or optics. As a young boy, Newton
spent time as an apothecary’s apprentice. He learned
to make medicines and potions that he used the rest
of his life. This may have been when he first devel-
oped an interest in alchemy. During the 17th century,
philosophers and scientists still believed that they

In 1815, a tooth from Sir Isaac Newton sold for a sum of £750 — that’s
about £66,225 or $82,935 today. The new owner had it set in a ring!

ABOVE: Newton, lost should be able to transmute one element into another.
in thought as he Such a process could bring great wealth to an indi-
contemplates the vidual who could, for example, change lead into gold.
apple at his feet, is They thought this secret knowledge had simply been
one of 28 statues in lost — and Newton believed he was just the man to
the main court of the rediscover it. He started experiments as an under-
Oxford University graduate and continued until at least 1693.
Museum of Natural
History. ANDREW GRAY/ Newton had always been secretive and mildly par-
anoid. In 1693 he wrote to Pepys complaining of feel-
WIKIMEDIA COMMONS ings of persecution, insomnia, memory loss, and loss
of appetite. He even accused his longtime friend of
RIGHT: One of spreading rumors about him and broke off their cor-
Newton’s more respondence, though he later apologized.
famous optical
experiments involved But according to two papers published in 1979 in
using a prism to split the Notes and Records of the Royal Society of London,
the Sun’s white light
into its component
colors. KELVINSONG/

WIKIMEDIA COMMONS

34 ASTRONOMY • DECEMBER 2019

These stamps were issued by the
U.K.’s Royal Mail service in March 1987
to celebrate the 300th anniversary of
Principia’s publication. They depict
Newton’s work with light and color, as
well as his characterization of gravity
and its description of the orbital
motion of bodies, which applies to
modern satellites and planets alike.

RAYMOND SHUBINSKI

these symptoms could have all been the result of included overseeing the industrialization and stan- ABOVE: Newton and his
mercury poisoning. Alchemists thought mercury dardization of the nation’s coinage. apple tree feature on
played a major role in the transmutation process, this 1930s collectable
and Newton used a lot of it. Heavy metal vapor must He was also charged with finding and prosecut- card, which was
have filled his rooms. He even drank the stuff and ing counterfeiters. This was not to Newton’s liking. packaged with Sunblest
complained of the aftertaste. It’s a miracle he lived. He protested the “vexatious and dangerous” duties Tea. RAYMOND SHUBINSKI
but was told they were part of the job description.
In 1979, scientists subjected strands of Newton’s So, as in everything else, Newton plunged into this LEFT: Queen Anne was
hair to neutron activation and atomic absorption work. He began to pursue these malefactors and see crowned in 1702, while
analysis. The results may explain the near mental that they were sent to the gallows. In his book Newton was Master of
breakdown the great scientist experienced in 1693. Newton and the Counterfeiter, Thomas Levenson the Mint. Coins such as
His hair, which the Earl of Portsmouth’s family had describes in detail Newton’s efforts to see such crim- this silver half crown
preserved for generations — the thinker’s niece had inals hanged. His words and actions indicate he may featuring Anne are
married into the family, and his relics had passed to have enjoyed seeing such rough justice done. It was renowned for their
her upon his death — showed elevated levels adherence to his
of mercury, up to 40 times higher than not uncommon for Newton to personally go stringent standards,
normal. High levels of lead and arsenic undercover in seedy bars and other areas enacted to reduce
were also present. of London in pursuit of his quarry. counterfeiting.
Newton was a complex man living
Capturing counterfeiters in a complicated age. It was a time ADAM CARR/ENGLISH WIKIPEDIA
when magic and science still inter-
When the post for Warden of the mingled, an age of tremendous intel-
Royal Mint opened in 1696, Newton lectual advancement and lingering
was offered the job; he was later ignorance. When Newton died, his
appointed to Master of the Mint in 1699. estate was worth more than $4 million in
He left the University of Cambridge for the
mint, which would be the final position he held today’s currency. Even with all this wealth,
during his life. Newton wore a gold ring set with a small but power-
ful magnetic lodestone, rather than some other
At the time, England’s currency was on the verge valuable gem. The ancient word lode means path or
of collapse due to rampant counterfeiting. For cen- journey, and Isaac Newton surely opened new paths
turies, coins had been struck by hand, leaving them along a complex and at times difficult journey.
with uneven edges. People would “clip” the edges
and keep the excess, thus devaluing the coin. It was Raymond Shubinski is a frequent contributing editor
also easy to counterfeit these coins. Newton’s duties to Astronomy with an interest in science history.

WWW.ASTRONOMY.COM 35

SKY THIS MONTH Visible to the naked eye
Visible with binoculars
THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY. Visible with a telescope
BY MARTIN RATCLIFFE AND ALISTER LING

A Geminid fireball
blazes through an
aurora’s glow above
Alaska’s Knik River
Area in 2017. This year,
the Geminid shower
peaks under a moonlit
sky. MATT SKINNER

December 2019

Gas giants bid a fond farewell

December brings the views of Mercury and Mars reveals Jupiter, Venus, and It still appears prominent
longest nights of the before dawn. Saturn strung out across nearly because it shines brightly at
year to people in the Northern 20° of sky. Jupiter hangs lowest, magnitude –1.8. The giant
Hemisphere. Normally, that Let’s start our tour soon standing just 7° above the hori- world sinks lower with each
would signal favorable condi- after the Sun sets December 1. zon 30 minutes after sundown. passing day, however, and
tions for backyard observers. A quick look to the southwest disappears into the Sun’s glare
But this year, all of the naked- during December’s second
eye planets cluster near the A delightful planetary alignment week on its way to solar con-
Sun in our sky, leaving a long junction on the 27th.
stretch of the night without any Saturn
bright solar system targets. Venus fares far better. On
December’s highlight has to SAGIT TARIUS Venus December 1, it shines at mag-
be the dramatic lineup of plan- Jupiter nitude –3.9 — seven times
ets in the early evening sky. brighter than Jupiter — from
While Venus dominates the 5° a perch 8° to the giant planet’s
view toward the southwest after upper left. You’ll have to wait
sunset, Saturn and Jupiter add December 1, 1 hour after sunset for the sky to darken some
a lovely flair to the scene early Looking southwest before you’ll be able to see
this month. Uranus and magnitude 0.6 Saturn, which
Neptune, which appear much Saturn, Venus, and Jupiter put on a stunning show in early December, though lies 11° to Venus’ upper left.
fainter than their closer cous- the gas giants disappear within a few weeks. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY
ins, appear higher in the sky Target Venus with binocu-
and remain visible through the lars December 2 and you’ll see
late evening hours. Eventually, one of the sky’s finest globu-
the long nights end with fine lar clusters, 5th-magnitude
M22 in Sagittarius, less than
1° to the north. A telescope

36 ASTRONOMY • DECEMBER 2019

RISING MOON I The young Moon’s lonesome sea

OBSERVING ON DECEMBER’S FIRST EVENING, Mare Mare Crisium and Cleomedes
HIGHLIGHT Crisium (Sea of Crises) dominates our view of the
waxing crescent Moon. The oval sea lies slightly Cleomedes
VENUS slides 1.8° due south north of the lunar equator and is the only fully
of SATURN during the early illuminated mare at this phase. Mare N
Crisium E
evening hours December 10. Just “inland” from Crisium’s northern shore
lies the 81-mile-wide crater Cleomedes. Named This month offers observers two
shows the planet’s 12"-diameter after a Greek astronomer who historians believe chances to view fine features on a
disk and 88-percent-lit phase. lived in the first century B.C., Cleomedes’ lava- waxing crescent Moon. CONSOLIDATED LUNAR
covered floor sports the hint of an off-center
Each night, Venus climbs a central peak and two craters between 6 and ATLAS/UA/LPL. INSET: NASA/GSFC/ASU
bit higher while Saturn sinks a 7 miles in diameter. Increase the magnifica-
little lower. The two are des- tion to see Rima Cleomedes, a long, thin appears 2° below brilliant Venus, both Mare
tined for a close encounter rille (channel) that cuts across the main Crisium and Cleomedes are half-lit.
December 10, when Venus crater’s northern half. Be patient for
passes 1.8° south of its moments of good seeing, when Earth’s When the Moon appears as a slender crescent,
companion. atmosphere steadies. These smaller fea- earthshine illuminates its “dark side.” It’s a good
tures disappear under the higher Sun that time to pick out features normally associated with
Saturn continues to lose comes the following few evenings. the Full Moon. Look for Tycho’s rays, the bright
altitude after this conjunction crater Aristarchus, the debris aprons surrounding
and becomes lost in the Sun’s You might be just as captivated watching the Copernicus and Kepler, and the darker seas.
glow before Christmas. Plan Sun set over this terrain in the evenings after
to catch your final telescopic December 12’s Full Moon. The reversed lighting
views of the ringed world in practically turns this into undiscovered country.
early December. On the 1st,
the planet’s disk measures 15" The Moon cycles through a complete set of
across while the rings span 35" phases every 29.5 days, so it returns to a waxing
and tilt 24° to our line of sight. crescent in the evenings leading up to New
Year’s. On December 28, the same evening Luna
Once Jupiter and Saturn
succumb to bright twilight, METEOR WATCH I Will the Bear steal the Twins’ show?
Venus rules the evening sky. On
December 18 and 19, it passes Ursid meteor shower DECEMBER BRINGS two notable
within 1° of the 9th-magnitude meteor showers. The Geminids —
globular cluster M75 on CASSIOPEIA Polaris URSA the best annual shower — peak
Sagittarius’ eastern edge. Venus MAJOR the morning of December 14.
crosses into Capricornus on the Unfortunately, the Full Moon arrives
latter date and spends the rest Radiant just two days earlier. The waning
of the month among the Sea gibbous Moon on the 14th lies in
Goat’s stars. A slim crescent CEPHEUS URSA Kochab Gemini, the constellation from which
Moon slides 2° below the planet MINOR the meteors radiate. Bright moon-
on the 28th, when the pair light will drastically cut the number
remain visible for more than DRACO of meteors, though observers with
two hours after sundown. a good sky who shield themselves
10° from the Moon might still see up to
Once Venus sets, turn your 20 meteors per hour before dawn.
attention to Neptune. The out- December 23, 1 A.M.
ermost major planet glows at Looking north By the time the Ursids peak the
magnitude 7.9 among the back- night of December 22/23, the Moon
ground stars of Aquarius the URSID METEORS A surge of up to 30 meteors has waned to a thin crescent and no
Water-bearer. That’s dim per hour could light up longer interferes. Although the
enough that you’ll need bin- Active dates: Dec. 17–26 the sky when this often- shower typically produces only
oculars or a telescope to spot it. Peak: December 22/23 overlooked shower peaks about 10 meteors per hour, major
Moon at peak: Waning crescent the night of December 22/23. outbursts occurred in 1945 and
— Continued on page 42 Maximum rate at peak: 1986 with smaller enhancements
reported as recently as 2011 and
10 meteors/hour 2014. Meteor experts predict a surge
of up to 30 meteors per hour could
happen this year, so it might be
worth braving the cold for a look.

WWW.ASTRONOMY.COM 37

STAR DOME N

HOW TO USE THIS MAP f

This map portrays the sky as seen URSA MAJOR ` _
near 35° north latitude. Located
inside the border are the cardinal d_
directions and their intermediate
points. To find stars, hold the map NE a`
overhead and orient it so one of
the labels matches the direction e
you’re facing. The stars above
the map’s horizon now match M81 M82 URSA
what’s in the sky. MINOR

The all-sky map shows LYNX _ Polaris
how the sky looks at: b
9 P.M. December 1
8 P.M. December 15 NCP k
7 P.M. December 31
Planets are shown C ` H b E C
at midmonth
Castor E _ SE _ NGC f EU P
MAP SYMBOLS Pollux C d
` L US S
Open cluster `ab
Globular cluster DA R O PA _
Diffuse nebula SIOPEIA
Planetary nebula g GEMINI S I L AM c
Galaxy a
_ A Cap_ella ¡ c 884 869 S A
STAR ` d PE NGC
MAGNITUDES U _`
` M38 R ¡
Sirius R
0.0 3.0 b
1.0 4.0 e
2.0 5.0
IG
STAR COLORS
A a
A star’s color depends
on its surface temperature.hc ¡+ M37 b
j
The hottest stars shine blue M35 A
d
•• Slightly cooler stars appear white N
• Intermediate stars (like the Sun) glow yellow
• Lower-temperature stars appear orangeCANIS MINOR M36 D M31
• The coolest stars glow red k
• Fainter stars can’t excite our eyes’ color` Algol l R

receptors, so they appear white unless you O
use optical aid to gather more light
` f ` M
BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT M1
www.Astronomy.com/starchart. a TAU R U S a

EDA

E c c Pleidades `

T

R `
b
I
_
A

N

ORION G M33

h ¡ U
_
_ A L
Betelgeuse
MONOCEROS HyaAdledsebaran R _ U

I E S M

` a

d PISCES a

/ h Uranus

` i _a
bd
¡ M42

c

_

g Rigel Mira
a `+
_` b A
a ERIDANUS
LEPUS CETUS

¡ o
`

_ FORNAX NGC 253
SGP
SCULP
_

SE

e

a _

PHOENIX

`

S

DECEMBER 2019 SAT.

SUN. MON. TUES. WED. THURS. FRI.

i DRACO a NW 1 234567
`
8 9 10 11 12 13 14

¡ `
_
LYRA 15 16 17 18 19 20 21 ILLUSTRATIONS BY ASTRONOMY: ROEN KELLY
Vega

a 22 23 24 25 26 27 28
M57

bd CYGNUS VULPECULA

_ Deneb ` 29 30 31
_
Note: Moon phases in the calendar vary in size due to the distance
d br from Earth and are shown at 0h Universal Time.

a

L A C E RTA ¡ M27
a
SAGIT TA
c Altair CALENDAR OF EVENTS

` _ DELPHINUS ` _a 2 Asteroid Pallas is in conjunction with the Sun, 9 P.M. EST
+d ` 4 First Quarter Moon occurs at 1:58 A.M. EST
AQUILA
The Moon passes 4° south of Neptune, 7 A.M. EST
W The Moon is at apogee (251,311 miles from Earth), 11:08 P.M. EST
8 The Moon passes 5° south of Uranus, 6 A.M. EST
c PEGASUS Enif M15 S 10 Venus passes 1.8° south of Saturn, midnight EST
12 Full Moon occurs at 12:12 A.M. EST
U 14 Geminid meteor shower peaks
15 Mercury passes 5° north of Antares, 11 A.M. EST
E 18 The Moon is at perigee (230,072 miles from Earth), 3:25 P.M. EST

L Last Quarter Moon occurs at 11:57 P.M. EST
21 Winter solstice occurs at 11:19 P.M. EST
a_ _ 22 The Moon passes 4° north of Mars, 9 P.M. EST

UU Ursid meteor shower peaks
26 New Moon occurs at 12:13 A.M. EST; annular solar eclipse
Q 27 The Moon passes 1.2° south of Saturn, 7 A.M. EST

E The Moon passes 0.6° south of Pluto, 10 A.M. EST
Jupiter is in conjunction with the Sun, 1 P.M. EST
e CAPRICORNUS 28 The Moon passes 1.0° south of Venus, 9 P.M. EST
_ 31 The Moon passes 4° south of Neptune, 4 P.M. EST

` WWW.ASTRONOMY.COM 39

AQUARIUS Path of the Sun (ecliptic)
PTOR
a

b

IS U S
ST
ISC R I N
AU
Fomal_haut P

SW Title Astronomy
Issue December 2019
Job # MAG-ASY-DEC19
Code PC
Proof 1
Date 8-15-19
Return 8-22-19

Illustrator erkelly
Designer
Art Dir.
Story Ed.

PATHS OF THE PLANETS

HER C Vn UMa LYN Comet
COM LMi GEM PanSTARRS
TRI
BOÖ AUR PER
CrB
LYR

LEO Path of the Moon Path of the Sun (ecliptic) ARI

Uranus

SER Astraea TAU
CNC
OPH
SER VIR CMi Vesta

Celestial equator

ORI

LIB MON
Mars
SCT CRT H YA ERI
ANT FOR
Sun CRV CMa LEP
Mercury CEN COL
PYX

SCO LUP PUP CAE
Dawn Midnight
TEL VEL

Moon phases

26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9

To locate the Moon in the sky, draw a line from the phase shown for the day straight up to the curved blue line.

THE PLANETS Uranus THE PLANETS IN THE SKY
Neptune
IN THEIR ORBITS These illustrations show the size, phase,
and orientation of each planet and the two
Arrows show the brightest dwarf panets at 0h UT for the dates
in the data table at bottom. South is at the top
inner planets’ to match the view through a telescope.

monthly motions and Jupiter
dots depict the outer Solar conjunction

planets’ positions at is December 27 Saturn

midmonth from high

above their orbits.

Venus

Mercury Mars Ceres

Earth Pluto
Winter solstice
is December 21

Mercury Venus PLANETS MERCURY VENUS
Mars
Date Dec. 1 Dec. 15
Ceres Magnitude –0.6 –3.9
Angular size 6.3" 12.2"
Jupiter Illumination 69% 86%
Distance (AU) from Earth 1.066 1.369
40 ASTRONOMY • DECEMBER 2019 Distance (AU) from Sun 0.362 0.728
Right ascension (2000.0) 15h06.7m
Declination (2000.0) –15°13' 19h41.5m
–23°12'

This map unfolds the entire night sky from sunset (at right) until sunrise (at left). Arrows DECEMBER 2019

JULYand colored dots show motions and locations of solar system objects during the month.

AND LAC Callisto 1
2
CYG HER Europa 3
4
LYR Io 5
6
PEG VUL Ganymede 7
8
SGE JUPITER’S 9
MOONS 10
Metis Amphitrite EQU OPH
PSC Eunomia Dots display 11 Callisto
AQL positions of
Neptune Galilean satellites 12
at 7 P.M. EST on
Venus passes 1.8° south the date shown. 13 Europa
South is at the
CET of Saturn on December 10 top to match the 14
view through a
SCL Saturn Jupiter telescope. 15 Ganymede Jupiter
PHE PsA CAP Venus Sun Io
16
SGR Pluto 17
Ceres 18
MIC 19
An annular solar 20
GRU DecTelciEpeLmseboecr c2Su6CrasOcross 21
22
Early parts of southern Asia, 23
evening Indonesia, Singapore, 24
25
and the Philippines 26
27
87654 3 2 1 28
29
31 30 29 28 27 26 25 24 30
31
Jupiter S
WE
Saturn
N

10"

Uranus Neptune Pluto

MARS CERES JUPITER SATURN URANUS NEPTUNE PLUTO

Dec. 15 Dec. 15 Dec. 1 Dec. 1 Dec. 15 Dec. 15 Dec. 15
1.7 9.1 –1.8 0.6 5.7 7.9 14.4
4.1" 0.4" 32.1" 15.4" 3.7" 2.3" 0.1"
97% 100% 100% 100%
100% 6.147 100% 100%
2.301 3.821 5.239 10.779 19.170 30.032 34.795
1.608 2.906 17h57.1m 10.037 19.821 29.933 33.939
14h57.7m 18h48.7m –23°18' 19h16.7m 2h02.6m 23h09.1m 19h33.7m
–16°20' –26°38' –22°10' 11°56' –6°34' –22°20'

WHEN TO

SKY THIS MONTH — Continued from page 37 VIEW THE

The Moon’s dramatic meeting with Venus of nearby guide stars makes it PLANETS

tricky to pinpoint. EVENING SKY

CAPRICORNUS Start with the Ram’s bright- Venus (southwest)
Venus est star: magnitude 2.0 Hamal Jupiter (southwest)
(Alpha [α] Arietis). Then locate Saturn (southwest)
magnitude 3.8 Alrescha (Alpha Uranus (southeast)
Piscium) 21° due south of
Hamal. If you draw an imagi- Neptune (south)
nary line between these two
MIDNIGHT
Uranus (west)

Moon stars, you’ll find Uranus about MORNING SKY

December 28, 1 hour after sunset 1° from the midpoint in the Mercury (southeast)
Looking southwest 5° direction of Alrescha. Mars (southeast)

Although Uranus has about

the same physical size as

Neptune, it lies 1 billion miles

A slender crescent Moon bathed in earthshine rises up to greet the sky’s closer to Earth, or a bit less than month, and its disk sports a
brightest planet during 2019’s final week. two-thirds as far away. Do the delightful blue-green color.

math, and you’ll find Uranus The night sky’s final two

Fortunately, Neptune rides 45° the Ram’s border with Pisces should appear slightly more planets don’t emerge until the

above the southern horizon as the Fish. Although it’s bright than 50 percent larger when approach of dawn. Mars appears

twilight fades to darkness and enough to be an easy target viewed through a telescope. It first, rising around 4:30 a.m.

doesn’t set until near midnight through binoculars, the lack does — Uranus spans 3.7" this local time December 1. The Red

local time. 94  The peak percentage of the Sun’s area the Planet shines at magnitude 1.7
The planet resides in the Moon hides during the December 26 eclipse. near the western edge of the
constellation Libra. About an
same binocular field as 4th- hour later, Mercury rises against
magnitude Phi (ϕ) Aquarii. On

December 1, Neptune lies 1.5°

west-southwest of this star. COMET SEARCH I A visitor receives a Hero’s welcome
Look for a 7th-magnitude field

star 0.9° due west of Phi. The

planet forms an isosceles tri- COMET PANSTARRS Comet PanSTARRS (C/2017 T2)
angle with these two stars. (C/2017 T2) strikes two notable

Neptune moves slowly east- poses in December as it continues N
ward relative to the starry back- its nine-month tour of the polar
ground during December. By sky. Researchers discovered this Path of 31
the 31st, it has closed to within comet as a 20th-magnitude fuzz- Comet PanSTARRS
1.1° of Phi. If you have a hard ball in October 2017 while survey-
time identifying the planet, CA ME LOPA RDA LIS
target your suspect with a tele-
scope. Only Neptune shows a 26
disk, which appears 2.3" across
and blue-gray in color. ing the sky with the Pan-STARRS1 21 Sharpless 2–205
Telescope on Haleakala in Hawaii.
Uranus proves to be an eas-
ier target. Not only does this Astronomers expect it to glow at E 16 _
planet shine brighter than 9th or 10th magnitude this month. h
Neptune, at magnitude 5.7, but 6
it also appears higher in the PanSTARRS spends most of Dec 1 11 NGC 1528 PERSEUS
sky. Uranus lies in the south- December among the background
east after darkness falls and stars of Perseus the Hero, a region +
climbs 60° above the southern that passes nearly overhead during b
horizon around 9:30 p.m. local the evening hours. If you have clear
time in early December. It
reaches the same position two skies, haul out a 4-inch or larger tele- 1°
hours earlier by month’s end. scope on the 14th or 15th and target

the star cluster NGC 1528. C/2017 T2 This cosmic interloper could reach 9th magnitude as it skirts the

shares a low-power field of view boundary between Perseus the Hero and Camelopardalis the Giraffe.

with the cluster both evenings. You’ll

need to boost the magnification quite a bit to see detail in the compact but high-surface-brightness comet.

The second photo opportunity comes the weekend of December 21 and 22. The comet then appears to

drift across the face of the sprawling emission nebula Sharpless 2–205. Think of the nebula as a fainter sibling

to the more famous Heart and Soul nebulae in Cassiopeia. PanSTARRS will pass near that pair in January.

The planet lies in a sparse The comet remains on the inbound leg of its elongated orbit around the Sun. Astronomers expect it to

region of southern Aries, near reach 7th or 8th magnitude at its closest approach in May 2020.

42 ASTRONOMY • DECEMBER

Burning ring of fire LOCATING ASTEROIDS I

Pursue a pebble in a pitcher

ASTEROID 15 EUNOMIA SPLASHES across the starry back-
drop of Aquarius the Water-bearer in December. Eunomia spends
the month within a binocular field of Alpha (α) Aquarii, a magni-
tude 2.9 star that lies about 20° southwest of the southwestern
corner of the Great Square of Pegasus. The asteroid glows at 10th
magnitude, however, so you’ll need a small telescope to pick it up.

Eunomia slides 0.8° south of Alpha on the 17th. But the aster-
oid saves its best encounters for 2019’s final week. It then passes
through the Water Jar asterism, a group of 4th- and 5th-magnitude
stars comprising Gamma (γ), Pi (π), Zeta (ζ), and Eta (η) Aqr.

To find Eunomia, use the finder chart below to zero in on its
approximate location and then sketch the half-dozen or so bright-
est stars you see through your telescope. Come back a night or
two later, and the “star” that has shifted position is the asteroid.

Italian astronomer Annibale de Gasparis discovered Eunomia
in 1851. With an average diameter of about 165 miles, it ranks
among the dozen biggest objects in the asteroid belt. Scientists
suspect it is the remnant of a larger body destroyed in a collision.

Eunomia grabs a drink of water

An annular solar eclipse December 26 should deliver superb views for those N
in parts of southern Asia and Indonesia as well as all of Guam. JATIN RATHOD PEGASUS

the backdrop of central Libra, As Mars moves eastward /
some 11° east of Mars. At mag- across Libra, it sets dead aim Path of Eunomia
nitude –0.6, the innermost on the 3rd-magnitude double
planet shines nearly 10 times star Zubenelgenubi (Alpha 31
brighter than its neighbor. Libra). On the morning of
December 12, the planet d 26 _
The gap between these two stands just 13' north of this c
worlds grows as the month star. View the pair with bin-
progresses because Mars is oculars or a telescope to see E 21 6
pulling away from the Sun a nice color contrast between a 16 k 11 Dec 1
while Mercury is drawing Zubenelgenubi’s whitish glow
closer. You can follow Mercury and Mars’ ruddy hue. A Q UA R I U S
throughout December’s first
half. It rises an hour before the You’ll also want to check 1°
Sun on the 15th, though it out the attractive pairing of a
stands only 6° high a half-hour waning crescent Moon with The Water Jar asterism in Aquarius forms a magnificent backdrop for
later. If you have an exception- Mars on December 22 and 23. this 10th-magnitude asteroid during the latter part of December.
ally clear sky and an unob- The Moon stands 9° above
structed horizon toward the Mars on the 22nd and 6° to the The Moon has three promi- Guam about an hour before
southeast, you might spot the planet’s lower left on the 23rd. nent encounters with solar sys- sunset. During an annular
1st-magnitude star Antares 5° tem objects in December: a eclipse, the Moon appears
to its lower right. Although Mars offers a conjunction with Mars on the slightly smaller than the Sun
visual treat on December 22nd and 23rd, an even closer and thus leaves a ring of sun-
The best views of Mercury mornings, it doesn’t look like pass by Venus on the 28th, and light visible. Viewers need to
through a telescope come on much through a telescope. The a spectacular meeting with the practice safe solar-viewing
December’s first few mornings. planet’s 4"-diameter disk shows Sun on the 26th. The final one techniques to avoid serious
It then shows a 6"-diameter no detail, and likely won’t for brings an annular solar eclipse eye damage.
disk with a gibbous phase. several more months. But to people along a narrow path
The planet moves away from things will improve next spring that touches parts of Saudi Martin Ratcliffe provides
Earth in the following weeks, as Mars heads toward an Arabia, Qatar, the United Arab planetarium development for
shrinking slightly as it waxes exceptionally good opposition Emirates, and Oman just after Sky-Skan, Inc., from his home
toward full. in October 2020. sunrise. The track then crosses in Wichita, Kansas. Alister
southern India and northern Ling, who lives in Edmonton,
GET DAILY UPDATES ON YOUR NIGHT SKY AT Sri Lanka in late morning; Alberta, has watched the skies
www.Astronomy.com/skythisweek. Sumatra, Singapore, and since 1975.
Borneo near midday; and

WWW.ASTRONOMY.COM 43

Cowboy Nicolas Silva
enjoys the total solar
eclipse on July 2 atop a
mountain ridge near
Cabalgatas Altos de
Cochiguaz, a ranch in
Chile’s Elqui Valley.

RICK ARMSTRONG

Chasing a

Peruvian nights, Incan sites,
and coronal lights were all
on full display during my
recent adventure through
South America. BY JAKE PARKS

or the better part of a year, I had been
eagerly counting down the days until I
would embark on my eclipse trip through
Peru and Chile. The adventure, sponsored by
Astronomy magazine in partnership with our tour company,
TravelQuest, provided an opportunity for nearly 300 partici-
pants to experience what many never get to witness with
their own eyes: a total solar eclipse.
The journey — which involved spending nights gazing
at the southern sky, tours of historic Incan sites like Machu
Picchu, and a trip to Cerro Tololo Inter-American Observatory
— culminated with my second-ever glimpse of the Moon
blotting out the Sun. And though the main event was unbeat-
able, the road there was nearly as brilliant.

Down through Peru

Following some initial travel troubles after my departure the

morning of June 23, including a missed connecting flight and

a checked bag orphaned in Miami, I ultimately made it to

Lima, Peru, by the wee hours of June 25.

With no fresh clothing and just a couple of hours before

our next departure, I immediately attempted to wash my

essentials in the sink. Surely, the hair dryer will help me dry my

damp clothing, I thought. And it did. But what I didn’t count

on was the resulting steam bath that

left me sweating ferociously as I intro- A staple of eclipse photog-
duced myself to my new TravelQuest raphy, this series shows the
International colleagues and clients. Sun’s shrinking crescent
(top right) morph into a
total eclipse (center) before
creeping back out again
(bottom left). MICHEL TOURNAY

WWW.ASTRONOMY.COM 45

After my soggy introductions, we northeast, providing us with a 1
set off for our flight from Lima to glimpse of two of the three bright 3
Cusco, Peru. Upon our arrival, we stars that make up the easy-to-spot
quickly hopped onto buses and asterism known (at least to us
headed north. On the way, we took northerners) as the Summer
a detour to visit a small, rustic vil- Triangle. We also spent a good deal
lage named Chinchero. Here, locals of time poking around the constel-
have perfected the art of weaving lation Scorpius, stopping to admire
Peruvian clothing, which is often the Scorpion’s glowing heart, the
made using alpaca, llama, or ruby-red star Antares.
sheep’s wool stained with naturally
colorful dyes. 1. Machu Picchu is hidden high in the
Peruvian mountains. The ancient Incan site
Next, we ventured onward to is thought to have been built in the 15th
our hotel in Peru’s Yucay District, a century as the summer home for Pachacuti
fertile farming region tucked away Inca Yupanqui, the ninth ruler of the
in the Andean highlands in an area Kingdom of Cusco. JAKE PARKS
also known as the Sacred Valley of
the Incas. Not only was the hotel 2. Two children in Peruvian clothing pose
there beautiful and packed with with their baby llamas on the narrow,
interesting native vegetation — cobblestone streets of Cusco, Peru. JAKE PARKS
such as the tamarillo, an egg-
shaped tree tomato — but the hotel
staff was also incredibly accommo-
dating. At night, they even shut off
many of the hotel’s lights so we
could carry out some southern
stargazing under Sacred Valley’s
extremely dark skies.

Exploring the 2 4
southern sky
Then there was the Milky Way
Because this was my first time in itself. Flanked above by a brilliant
the Southern Hemisphere, I initially Jupiter and below by an easily vis-
struggled to orient myself under ible Saturn, the cosmic river flowed
the new celestial tapestry — and across the dark sky with striking
the sheer number of stars visible clarity. We paid particular atten-
without significant light pollution tion to the Milky Way’s shadowy
didn’t help me get my bearings. voids, caused by light-blocking gas
Fortunately, the stars Alpha and and dust between us and the bil-
Beta Centauri are fantastically easy lions of stars in our galaxy’s disk.
to spot. Aptly nicknamed “The For the ancient Incas, these dark
Southern Pointers,” these bright clouds, rather than outlines traced
stars served as a guide to the go-to by bright stars, formed their
target for most first-time southern constellations.
observers: the constellation Crux
the Southern Cross. Specifically, we had a great view
of the Incan constellation Yacana
After briefly dissecting the
Southern Cross, we targeted the
nearby globular cluster Omega
Centauri (NGC 5139) through one
of the many telescopes brought by
the tour participants. From there,
we hopped around the sky tracking
down some of the brightest stars,
such as Spica in Virgo. A short
time later, we were treated to views
of Vega and Altair as they rose
above the mountains to the

46 ASTRONOMY • DECEMBER 2019

the Llama, whose two glowing eyes reclining back on a bench to take
are marked by Alpha and Beta everything in when a friendly
Centauri. This massive dark con- hotel employee wandered up and
stellation spans some 40° from tip asked, “¿Tranquila, sí?” And it
to tail and was thought to be a truly was. There are only a hand-
shadow cast by a great llama drink- ful of times in my entire life that I
ing from the cosmic river that is remember being in such a relaxed
the Milky Way. Upside down and and peaceful place.
below the Llama is its nursing cria,
the Baby Llama. Ancient Incan ruins

Perched between the Llama and The next day, June 26, we packed
the Southern Cross is Yutu the our bags and boarded a train to
Tinamou (a ground bird similar to the town of Aguas Calientes, unof-
the partridge), which is also known ficially known as Machu Picchu
as the Coalsack. To the lower right Pueblo. This small but bustling
of Yutu sits Hanp’atu the Toad, so village is located in a valley below
named because its arrival in the the famous Incan ruins of Machu
morning sky near the end of Picchu, which were built around
October corresponds with an the 15th century.
increase in the croaking of toads,
which the Incas thought signaled After a quick lunch, we boarded
coming rain. a bus that took us up the narrow
and winding road to Machu
Beneath this incredibly dark Picchu. Upon arriving at the
southern sky, accompanied by the entrance of the ruins, I was ini-
sounds of countless stray dogs tially taken aback by the swarms of
arguing in the distance, I felt a visitors clamoring to both enter
sense of serenity wash over me as and leave the site. Fortunately,
I gazed upward. In fact, after our within just minutes of entering,
impromptu star party, I recall the scores of tourists thinned out

3. Incan stonework, like that on display at Machu Picchu I felt a sense of serenity wash over me
and the fortress of Sacsayhuaman (pictured here), often has as I gazed upward.
interlocking joints that help prevent the walls from
collapsing during the many earthquakes that frequent the as we explored the roughly 200
region. JAKE PARKS buildings spread over some
20 acres of concentrated ruins.
4. Local weavers assemble handmade clothing using dyed When examining the buildings up
alpaca, llama, and sheep’s wool in the small village of close, you could see that many of
Chinchero. JAKE PARKS the huge stone blocks interlocked,
like simple puzzle pieces. Our tour
5. Machu Picchu’s Temple of the Sun (bottom left) has two guide explained that this technique
trapezoidal windows that each align with the Sun at first helped prevent the buildings and
light during either the summer or winter solstice. JAKE PARKS walls from collapsing during the
region’s many earthquakes.

Also within these ruins was a
particularly notable structure: the
famed Temple of the Sun. While
most of Machu Picchu’s buildings
have rectangular foundations, the
Temple of the Sun has a semicircu-
lar design that includes two small
trapezoidal windows. These are
precisely oriented so that sunlight
passes perfectly through one win-
5 dow during winter solstice and the
other during summer solstice.

WWW.ASTRONOMY.COM 47

Surprisingly, the town below makeshift car show exemplified 2
Machu Picchu was almost as the Peruvian spirit and energy that
fascinating as the ancient ruins. permeates the entire city. 1. At the end of totality, Baily’s beads, which
Although its primary purpose occur when sunlight squeaks through
clearly was to tend to Machu Onward to Chile valleys on the limb of the Moon, popped
Picchu’s roughly 1.3 million annual into a brief existence. STEPHEN MOORE
tourists, this did not diminish the Of course, as soon as I started
town’s appeal. In addition to getting used to Cusco’s altitude, 2. Over the course of just a few hours, the
countless shops, there were many it was time to press on to Chile. Sun transformed from a full disk to a thin
restaurants with delicious food, as Specifically, we flew to the twin crescent to a glowing corona before finally
well as a town square centered cities of La Serena and Coquimbo, setting behind a mountaintop with a chunk
around a statue of Pachacuti Inca located on the coast of the South of its disk still missing. STEPHEN MOORE
Yupanqui. This ninth ruler of the Pacific. These two cities, each with
Kingdom of Cusco, whose name a population over 200,000 and 3. Avid eclipse chaser and photographer
roughly translates to “Earth- separated by only about 8 miles Michel Tournay playfully dons a mask while
shaker,” is often credited with (13 km), would serve as our home standing in front of his equipment in the
establishing the Incan Empire base for the eclipse. hours before totality on July 2. SUSAN PETRY
through conquests of the Cusco
Valley and beyond, eventually The day after our arrival, 4. By placing a black, rubberized mosquito
expanding the Incan reach in June 30, we were largely left to our net in front of his lens, the photographer
western South America. According own devices. This allowed me to captured this image of the first diamond
to many archeologists, Machu explore the local markets, as well ring with a beautiful diffraction pattern.
Picchu itself was built as a summer as casually stroll along the nearby
home for Pachacuti. beaches, where I unexpectedly MICHEL TOURNAY
found myself within just a few feet
After spending the night in of a pair of resting sea lions. 5. Local schoolchildren joined our
Aguas Calientes, we returned to TravelQuest group at a soccer field in
our previous hotel in Sacred Valley By July 1, our anticipation of the Vicuña to share the experience of
on June 27, where we took advan- eclipse had reached a fever pitch. In witnessing a total solar eclipse firsthand.
tage of another beautiful night to the morning, we distracted our-
again dissect the southern sky. The selves by going on a walking tour JAKE PARKS
next day, we made a quick stop at through La Serena. And that night,
the ancient hilltop fortress the nearly 300 people in our group
Sacsayhuaman, which means “the
place where the hawk is situated,” 1
before venturing to the bustling city
of Cusco below, located just over a met for a fantastic dinner supple-
mile (2 kilometers) to the south. mented by pre-eclipse talks by Paul
Deans, a freelance astronomy
Situated at an elevation of about writer and editor with more than
11,200 feet (3,400 meters), Cusco is four decades of experience; Jay
more than 3,000 feet (915 m) Anderson, a meteorologist who
higher than the ruins of Machu specializes in predicting weather
Picchu. Though this may not seem for eclipses; and me.
like much, I and many others
noticed the difference. Because Eclipse day
many of our group had already
passed around a communal cold, Then came July 2, 2019: The day of
the altitude was the final straw that the Great South American Eclipse.
put some of us on our backs. But
while I was acclimating, many
embarked on a walking tour of the
historic city, which has steep and
narrow cobblestone roads that vein
through beautiful colonial-era
buildings often built atop ancient
Incan foundations. By nightfall, I
willed myself to explore the city
and ventured to the nearby town
square, Plaza de Armas, where a

48 ASTRONOMY • DECEMBER 2019 5

To avoid all the visitors flock- blocking our view from La Serena, dozens of eclipse chasers and pho-

ing to Chile (the population of La most of us opted to travel to our tographers ample time to set up

Serena more than doubled in the preplanned eclipse-viewing site their equipment. And boy, did they

days leading up to the total solar about 40 miles (65 km) east of La bring equipment.

eclipse), we got off to an early Serena, near a city called Vicuña. Scattered across the soccer field

start. Due to the possibility of sea- Here, the local climate tends to were more than 100 telescopes and

sonal coastal clouds rolling in and produce fewer late-afternoon tripod-mounted cameras, and even

clouds, which is why we had one handmade and self-designed

secured a soccer field that would spectroscope. The atmosphere at

provide a primo view of the eclipse. the site was electric. As we all

Although we had exclusive access patiently — albeit anxiously —

to the site, TravelQuest made sure awaited totality, some spectators

to invite local schoolchildren, as casually tossed frisbees, while oth-

well as some local vendors, to join ers enjoyed impromptu dance ses-

us for what is usually a once-in-a- sions. Many others, however, were

lifetime experience. entirely focused on ensuring their

To ensure we would beat equipment was ready to go. But this

eclipse-related traffic, we left La didn’t stop them from inviting

Serena for the soccer field first those without equipment to sneak

thing in the morning, even though peeks at the increasingly crescent-

the main event wouldn’t occur shaped Sun (while using solar fil-

3 until about 4:38 P.M. local time. ters, of course).

Fortunately, the traffic was rela- The closer we got to totality, the

tively mild, which meant we quieter everyone seemed to get.

arrived with about seven hours to Then, just a few minutes before the

spare before first contact — when Moon completely obscured the

the Moon first starts its slow trek Sun’s disk, the chatter picked back

across the Sun. This gave the many up with a vengeance.

Scattered across the soccer field were
more than 100 telescopes and tripod-
mounted cameras, and even one handmade
and self-designed spectroscope.

4