Astronomy 02.2021

Amateurs at work target using high-throughput variations from different This discovery image of a stellar
Ultra-deep observations of luminance (clear) filters for sources. These artifacts com- stream in the halo of the nearby dwarf
nearby spiral galaxies and visible-light imaging. To plicate or mask the detection starburst galaxy NGC 4449, located
regions around them have capture fuzzy emission line of faint structures, and their 12 million light-years away in the
been obtained by world-class structures in galactic halos, correction adds significant constellation Canes Venatici,
American, European, and imagers use narrowband observing time overhead to was detected with deep, integrated-
Chilean amateur astroimag- Hydrogen-alpha filters. the data-gathering process. light images from a 20-inch amateur
ers. They operate privately telescope. R. JAY GABANY
owned observatories that These observations demon-
use high-quality apochro- strate in several ways the fea-
matic and Ritchey-Chrétien sibility of smaller telescopes to
telescopes with apertures detect very faint diffuse struc-
between 4 and 32 inches (0.1 tures in large fields around
and 0.8 meter). Each observ- nearby galaxies. First, small
ing location features spectac- short-focal-length telescopes
ularly dark, clear skies with combined with single-chip
typical seeing less than 1.5". cameras cover a larger field
of view. Second, the use of
These modest telescopes single-chip detectors also
— and, in some cases, makes it easier to flatten the
telephoto lenses — are coupled external regions around
with off-the-shelf CCD cam- galaxies in comparison to
eras equipped with the latest standard multi-chip detector
generation of imaging chips. arrays used with professional

THE STANDARD MODEL OF THE
UNIVERSE’S FORMATION PREDICTS
THAT THE ELEGANT GALACTIC SPIRALS
WE SEE TODAY, INCLUDING OUR OWN
MILKY WAY, AROSE HIERARCHICALLY.

They can probe vast sky areas telescopes. Finally, observa- Searching for stellar Stellar streams around M63 are
with unprecedented depth — tions with large telescopes are streams the remnants of a satellite galaxy
approximately three magni- sometimes subject to glare that was disrupted by the large
tudes fainter than either classic from nearby bright stars and Computer simulations pre- spiral. Their presence was confirmed
photographic plate surveys significant sky background dict that the stellar halos of in this image, taken with a 20-inch
like the Palomar Observatory massive galaxies contain an amateur telescope located high in
Sky Survey or more recent the Sacramento Mountains of
digital surveys like the Sloan New Mexico. R. JAY GABANY
Digital Sky Survey (SDSS).
WWW.ASTRONOMY.COM 51
Camera sensitivity, fast
operation, and lack of the
competition for observing
time typical of professional
observatories places these
low-cost robotic amateur
facilities at the front line of
ultra-deep imaging. They
allow high-impact research
of structures in nearby
low-surface-brightness galax-
ies. Doing so requires mul-
tiple seven- and eight-hour
exposures of each galactic

These clear luminance filter
images of nearby galaxies from the
Stellar Tidal Stream Survey show
large, diffuse light structures in their
outskirts. A color inset of the disk of
each galaxy has been over-plotted
for reference. D. MARTÍNEZ-DELGADO/

R.J. GABANY/K. CRAWFORD/K. TEUWEN/A. BLOCK/

J. SCHEDLER/M. HANSON

Located in the constellation
Leo, extensive debris shells from
the accretion of one or more
long-gone satellite galaxies
encompass spiral galaxy NGC 3521
like a bubble. Data for this image
were collected through a 20-inch
amateur telescope. R. JAY GABANY

assortment of tidal debris requires long-exposure, faint structures is compelling many thousands of light-years
streams that long exposures wide-field images encom- evidence that supports the into space, often on both sides
should reveal. The most spec- passing the outskirts of the hierarchical nature of galaxy of the host galaxy.
tacular examples are those host galaxies. Working with formation predicted by the
that wrap around the host amateur astroimagers over standard cosmological model. We have also found iso-
galaxy and roughly trace the the last decade, we have lated shells, giant clouds of
orbit of the progenitor satellite imaged nearby spiral galaxies In addition to circular fea- debris floating within halos,
galaxy that created them. as part of the Stellar Tidal tures similar to the Sagittarius jetlike spikes emerging from
Stream Survey. stream surrounding the galactic disks, giant plumes,
These streams cannot be Milky Way, our data have and large-scale diffuse struc-
resolved into individual stars This observational effort revealed enormous structures tures. All of these are possibly
and thus appear as elongated, has discovered almost 50 resembling open umbrellas related to the remnants of
diffuse light features with previously undetected tidal with long, narrow shafts. ancient satellites that are now
an angular extent of several streams around our targets. These terminate in a giant thoroughly disrupted.
arcminutes. Detecting them The extraordinary variety of shell of debris extending
One important highlight
of this survey was the discov-
ery of a stellar stream around
NGC 4449, an isolated irreg-
ular galaxy similar to the
Large Magellanic Cloud. This
is the lowest-mass galaxy with
a verified stellar stream. Such
a discovery suggests satellite
accretion also can play a sig-
nificant role in building up
stellar halos around low-mass
galaxies as well as possibly
triggering starbursts.

Discovering satellite
galaxies
Searching for stellar streams
with deep amateur images
has also led to the discovery
of numerous faint dwarf sat-
ellite galaxies around a hand-
ful of nearby spirals. This is

52 ASTRONOMY • FEBRUARY 2021

intriguing because sophisti- This image presents in
cated computer simulations outstanding detail an extended stellar
predict a large number of tidal stream wrapping around the
small dark matter halos in the edge-on spiral galaxy NGC 5907,
local universe. But our theory located about 53 million light-years
of galaxy formation is still away in the constellation Draco the
unclear as to how many of Dragon. This picture shows how the
these are in the form of lumi- accretion of a low-mass satellite
nous star systems. Therefore, galaxy can produce an interwoven,
rosettelike structure of debris
dispersed in the halo of its host
galaxy. R. JAY GABANY

astronomers want to conduct

a full inventory of dwarf gal- low-cost telephoto lenses to

axies, both those orbiting as obtain deep images of the

satellites and isolated dwarfs Clouds. One panoramic view

that are in the vicinity of revealed a never-before-seen,

nearby massive galaxies. The dense, shell-like area of stars

only way to detect them is by in the outskirts of the Small

surveying vast regions with Magellanic Cloud.

deep images. Research using photomet-

Only a few organized astro- ric observations from the

imaging groups are searching Survey of the Magellanic

for low-surface-brightness Stellar History revealed the

satellite galaxies. Some mem- shell is mainly composed of

bers of the Stellar Tidal young stars. It suggests the

Stream Survey are also structure resulted from a

involved in the Dwarf Galaxy star-formation event, likely

Survey with Amateur triggered by gravitational

interaction with the Large

ISOLATED DWARF SPHEROIDAL GALAXIES ARE MADE Magellanic Cloud and/or the

EXCLUSIVELY OF OLD STARS WITH LITTLE GAS TO FUEL Milky Way about 150 million
STAR FORMATION. years ago. Recent studies
with the Hubble Space

Telescope found the two

Telescopes. Additionally, the astroimager Giuseppe the Milky Way’s two larg- Magellanic Clouds had a

Tief Belichtete (Very Long Donatiello during a visual est galactic satellites, the head-on collision about

Exposed) Galaxies project is inspection of a deep image Magellanic Clouds, through the same time.

run by German and Austrian produced with a 5-inch mapping their outskirts.

imagers. These groups look refractor. The discovery was These regions should still Can amateurs

for dwarf galaxies in subsequently confirmed with contain clues about past inter- contribute?

long-exposure images using SDSS images and follow-up actions between the Clouds Based on these results, it’s

software that searches for observations by the 3.6-meter that left visible imprints such clear that advances in our

likely candidates and then Galileo and the 10.4-meter as distortions, clumps, arcs, understanding of galaxy for-

extracts their photometric Gran TeCan telescopes, both and dense stellar areas. mation needn’t be obtained

and structural characteristics. located in the Canary Islands. With that purpose in only by large, professional

Isolated dwarf spheroidal This low-surface-brightness mind, we performed a deep, instruments. Important sci-

galaxies are made exclusively stellar system, located about wide-field imaging survey entific results that further

of old stars with little gas to 1° from Mirach (Beta [β] of the periphery of the our understanding of how

fuel star formation. These Andromedae), is suspected Magellanic Clouds. Inspired the universe formed can be

distant star systems are of to be the most isolated dwarf by the photographic plate obtained when amateurs with

huge interest because they galaxy in the Local Group. work of French astronomer modest telescopes collaborate

act as laboratories where Gérard de Vaucouleurs in the with professionals with big

astronomers can study why Magellanic Cloud ’50s, this modern project used objectives.

they stopped forming stars interactions

about 10 billion years ago. Another important approach David Martínez-Delgado is an astrophysicist at the Instituto de

For example, Donatiello I to understanding the for- Astrofisica de Andalucia in Spain who detects galactic fossils around

is a dwarf spheroidal galaxy mation and evolution of nearby galaxies. R. Jay GaBany is an award-winning California

discovered by Italian dwarf galaxies is studying astroimager.

WWW.ASTRONOMY.COM 53

We review

Celestron’s

60th

WHEN I WAS A TEENAGER, new

to observing the sky, I spent a year wan-
dering across the Milky Way armed with
nothing more than a pair of 7x50 binocu-
lars. Then a miracle happened: I received
a Celestron 8, 1976 vintage, as a birthday
present. It changed my universe forever.

From the cornfield behind our Ohio
subdivision, the telescope opened up
completely new vistas — star clusters,
nebulae, and galaxies. Not only could I
see hundreds of spectacular sky objects,
but I was seeing things like the Veil Nebula,
which the old-fashioned literature of the
time contended was beyond the reach of an
8-inch scope.

Now I feel like I have undergone another
telescope revolution. Last year Celestron
celebrated its 60th anniversary. As part of
their festivities, they produced a new 8-inch
Schmidt-Cassegrain Telescope (SCT), one
that rolls all of the company’s fanciest fea-
tures into one package.

With a built-in wide-field camera, it
aligns itself in a matter of minutes, requiring

The telescope’s carbon-fiber tube is both lightweight and
very strong, giving this model a high-tech appearance.

Celestron’s most sophisticated 8-inch SCT ever features a
revolutionary system that aligns itself so that users can simply
punch in object names and designations on a keypad and slew
to thousands of targets.

The NexStar Evolution 8HD With StarSense, a limited-edition telescope,
combines all of Celestron’s fanciest trappings to produce a superb, top-of-the-line
instrument. BY DAVID J. EICHER // IMAGES BY CELESTRON

anniversary C8

minimal knowledge on the part of the PRODUCT INFORMATION Out under the stars
user. It then slews to any of 40,000 targets The first thing you need to do with this
within its onboard computer’s database. Celestron Limited-Edition scope is set it up on level ground and run
Its multicoated optics are of the highest NexStar Evolution 8HD Telescope a program that enables the StarSense unit
caliber, and the three included eyepieces With StarSense, to calibrate itself. Included instructions
are sensational. This is the ultimate 60th Anniversary Edition and a link to an online video tutorial
8-inch SCT of its time, and I was happy make that very simple. That first night
to be able to put it through its paces over Type: Schmidt-Cassegrain reflector I was in a hurry, so I set it up on my
the past few weeks. Aperture: 8 inches (203 mm) driveway to give it a quick run-through.
Focal length: 2,032 mm Although a portion of the sky was
Setup and inspection Focal ratio: f/10 blocked by a tree and the house, I was
Assembly was relatively straightforward, Optical tube length: 17 inches (43.2 cm) curious to see what would happen.
and a helpful booklet walks owners Weight: 42 pounds (19 kg) fully
through the process. I went slowly, read So began my adventure with StarSense
everything carefully, and within an hour assembled Autoalign. The camera mounts atop the
had everything set up in my living room Price: $2,599 scope’s tube with a heavy bracket and
for inspection, charging of the onboard Contact: Celestron plugs into a port on the mount. To begin
battery, and preparation for a night of the calibration procedure, you start with
observing. 2835 Columbia St. the scope’s tube positioned horizontally.
Torrance, CA 90503 A hand controller allows you to input
With the telescope assembled, I 310.328.9560 choices and, once the scope is aligned,
couldn’t help but be struck by its quality www.celestron.com target countless objects. I uncorked the
and elegance. It features a
carbon-fiber tube; multicoated, Celestron supplies an array of accessories with scope’s mirror, the StarSense cam-
high-transmission optics (what this scope, allowing users to enjoy a luxurious era’s cover, and the diagonal’s
Celestron calls “Edge HD”); a telescopic experience. cover before plopping a very nice
sturdy single-arm mount; and, of E-lux 32mm Celestron eyepiece
course, the alt-azimuth mounting objects manually for years. Would this into the diagonal.
enabled by the computer control of computer-controlled system with its
the scope. The company seemingly database of tens of thousands of objects I powered the scope on, chose
spared no details: The machining — which it would apparently use to align “Align” on the hand controller, set
is top-notch and the hardware is itself before hopping between galaxies the time, date, and time zone,
solid, a 2" focuser and star diago- — win me over? then stepped back and watched.
nal came along with the package, Over the course of about
and the tripod is heavy duty. The 10 minutes, the scope slewed to
onboard battery holds a charge for and fro and occasionally noted on
more than 10 hours at a time. The the controller that it had imaged a
included eyepieces are very nice, with a certain number of stars. Would
2" 32mm “porthole” for deep-sky observ- this work with the handicap I gave it in
ing and higher-power 1¼" eyepieces of my rush to test the scope? After a short
15mm and 9mm focal lengths. time, “Alignment complete” came up on
the controller.
The StarSense system was really what Next, I followed the protocol by cali-
intrigued me. I am an old-school, brating on a known star. I punched in
star-hopping guy who has taken great “Vega” and the scope immediately slewed
pride in learning the sky and finding upward, capturing Vega’s position. When
I peered into the eyepiece — low power,

WWW.ASTRONOMY.COM 55

no doubt — the star was dead center. The Celestron’s StarSense system uses a remarkable makes one spoiled quickly. There was
final step is a calibration on the star itself wide-field camera to image star patterns around the the Trifid, glowing faintly; the unmis-
(Vega in my case), and this can be done sky, allowing the telescope to understand where it is takably bright Omega Nebula popped
with a high-power eyepiece to maximize and how it’s aligned before automatically slewing to fiercely, and the delicate light of the
precision. You can then realign the a target. Eagle Nebula appeared well defined.
StarSense and, in another few minutes, The computer-controlled database
the mount is ready to use all night; you makes punching in some of the
can simply punch in targets and let the lesser-known objects like clusters M23,
scope slew to them. M25, and NGC 6603 easy. I worked my
way up to M11, which was incredible,
This full calibration procedure needs and then viewed some globulars — M22
to be performed only once, when the in particular was a killer, looking quite
StarSense Autoalign is first attached to the photographic.
telescope’s tube. From there, a full calibra-
tion is not needed unless the StarSense is I turned toward some favorite plan-
bumped or the bracket removed. etary nebulae I hadn’t viewed in a while.
The Dumbbell Nebula, high in the sky,
Wow. Here is the kind of telescope knocked my socks off — it looked like a
that could revolutionize astronomy. This glowing photo in a rich starfield of col-
is a telescope that anyone can use without orful suns. What incredible beauty. But
any knowledge of old-style polar align- Cygnus and Aquila had many other
ment. It is really quite amazing to see this treasures, and I viewed NGC 6781,
work just as magically as is advertised, NGC 6894, NGC 7008, and NGC 6826
with objects showing up dead-centered, (just to name a few). They all appeared
just as requested from the database. quite well defined, with the blue-green
colors showing well, and were visible at
Computer-controlled The scope’s standard visual back employs a low powers, growing more spectacular as
heavens 2" star diagonal and can accommodate both 2" I increased magnification.
I gave this telescope a more thorough and 11/4" eyepieces.
test run from my backyard in Wisconsin, I then took a shot at some widely scat-
where I can see the Milky Way and a The Lagoon Nebula did not disap- tered objects just to see the range of
good smattering of faint stars. The tele- point, with its gauzy areas of bright views the telescope could provide. The
scope performed most impressively. I gray-green nebulosity and the sparkly, Andromeda Galaxy appeared bright and
can’t wait to get it underneath a really well-populated star cluster NGC 6530. oval, with well-defined dust lanes close
prime sky like that of southern Arizona. For a time, I walked up the line of bright to the nucleus. The Owl Cluster in
clusters and nebulae in Sagittarius and Cassiopeia, with its bright deep yellow
I commenced my journey with Jupiter Serpens. Only needing to input the chief sun, was an old friend I revisited.
and Saturn, each looking really fine, with numbers of Messier and NGC objects Double stars like Mizar and Albireo were
nice cloud details, even at low power. All simply stunning, set in black starfields,
the moons that should have been present and galaxies like M81 and M82 floated
were, and the higher-power eyepieces majestically in space.
provided a splendid view early on, even
though the seeing had not fully settled As the night went on, I found this
down for the evening. telescope to deliver on everything I had
hoped for: The optics are sharp, the
But I was eager to tour deep-sky objects accessories luxurious, the tripod over-
and so I plopped the 32mm eyepiece back built and very stable, the craftsmanship
in and went to work. Everything I looked of the optical tube and the electronics
at showcased the quality of the telescope’s first-rate. I have a soft spot for the old
optics — the views were crisp and well 1976 Celestron 8, with which I made my
defined, and I saw all the details in clus- initial thousands of observations, and
ters, nebulae, and galaxies that I would which is now in my basement. But
expect to see from a suburban site. The there’s a new Celestron in town, and this
32mm eyepiece provides a sharp, flat field, magnificent model is going to be hard
yielding crisp stars all across the view. for any such portable instrument to
overcome. This is a telescope for a new
At press time, Celestron had announced that they have sold out of this exclusive anniversary age of amateur astronomy.
model. However, almost exactly the same telescope — without the carbon-fiber tube and a few
bells and whistles — is available. The Celestron NexStar Evolution 8HD With StarSense functions David J. Eicher is editor of Astronomy
in exactly the same way as the anniversary edition. You can find out more about it here:
www.celestron.com/products/nexstar-evolution-8-hd-telescope-with-starsense. and has been using telescopes for more

than 40 years.

56 ASTRONOMY • FEBRUARY 2021

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Astronomy.com

SECRET SKY LEFT: On June 10, 2020, an with only a partial penum-
Earth-sized sunspot, AR bra that doesn’t completely
A sunspot bino 2765, from brewing solar surround the core; and fully
challenge cycle 25 could be seen dressed sunspots, which are
through handheld 8x42 Earth-sized and feature a
Search for small spots with both eyes. binoculars. RIGHT: Two dark core, an umbra, and a
days later, when the
spot’s umbra was smaller

and less apparent, it was penumbra.
difficult to see, even when I began systematically
the author braced the
binoculars. North is up observing the Sun on

and east to the left. SDO/HMI June 10, 2020. That day, I

used handheld 8x42 binocu-

lars to see without difficulty

a fully dressed Earth-sized

sunspot labeled AR 2765.

(AR stands for active region.)

The evolved spot was in the

Sun’s southern hemisphere

and had already sailed past

the central meridian.

Two days later, the fore-

shortened spot appeared both

For safe binocular smaller and less apparent,
solar viewing, you can
make a simple device The long-awaited next solar cycle is showing making it more difficult to detect. Only when I braced
using certified signs of awakening, and so is the time for
eclipse-viewing observers to search for naked-eye sunspots. the binoculars against a wooden post could I resolve the
glasses, scissors, and But at the beginning of a new cycle, the first spots to
glue or tape. Cut and appear are generally too small to be detected without spot, which looked more smoky gray than black.
fit the glasses into a optical aid. Using safe solar filters in front of binoculars
cardboard box large will help bring some of these devilishly delightful spots A similar situation occurred July 25, when another
enough to fit over into view. Unfortunately, the task is not easy.
the front of your Earth-sized sunspot (AR 2767) appeared in the Sun’s
binoculars. Make sure Cycle 25 brewing?
the fit is secure and southern hemisphere. As for AR 2765, handheld 8x42
that there are no light In their February 2020 article in Research Notes of the
leaks. STEPHEN JAMES American Astronomical Society, Dibyendu Nandy from binoculars easily brought it into view. It remained vis-
the Center of Excellence in Space Sciences India and his
O’MEARA colleagues argue that solar cycle 25 may be dawning. ible until July 31, when the spot’s highly foreshortened
No one knows exactly how a new solar cycle starts, but
BY STEPHEN it’s thought to be based in a complex interaction of ion- umbra diminished in apparent size enough that it
JAMES O’MEARA ized gas and the Sun’s magnetic field. We do know that
Stephen is a globe- spots in a new cycle will have their magnetic poles became a challenge to see through the binoculars. It
trotting observer who reversed from those in the last cycle — in this case, cycle
is always looking 24, which ended around December 2019. vanished from view the next day.
for the next great
celestial event. Since November 2019, solar astronomers have been By August 5, a more challenging spot (AR 2770) in
observing new sunspots with reversed polarity around
25˚ north and south latitudes. And this happens to be the Sun’s northern hemisphere had slid into binocular
exactly where they expected new spots from solar cycle
25 to appear. Seeing such spots is a positive sign that a view. That day, the foreshortened spot was difficult to
new solar cycle is in the making.
see even with braced 10x50 binoculars. I had to know
The binocular challenge
exactly where to look to pick it out. Sighting AR 2770
Before we get into viewing cycle 25 sunspots, two defi-
nitions. A sunspot’s umbra is the dark inner part. Its was similar to spotting Venus in the daytime — if you
penumbra is the lighter outer region. Currently, the
stammering start of cycle 25 has been creating three look away for an instant, it’s gone.
types of spots: Short-lived naked cores, which are state-
sized dark spots without any penumbra; partially Two days later, however, the Earth-sized spot was a
dressed proto-sunspots, which are Moon-sized marks
cinch through handheld binoculars. I finally lost sight

of it on August 11, the day after an enigmatic light

bridge had split the spot in two, and before it had

dwindled into a naked pore.

Observe in sunlight

By the time you read this, other Earth-sized spots may
be moving across the Sun. Each offers you a chance to
test your direct vision through filtered binoculars. I
want to learn how small of a sunspot you can see, espe-
cially if you use tripod-mounted binoculars or those
larger than 10x50. Good luck, and, as always, send what
you see and don’t see to [email protected].

BROWSE THE “SECRET SKY” ARCHIVE AT
www.Astronomy.com/OMeara

58 ASTRONOMY • FEBRUARY 2021

BINOCULAR UNIVERSE

Bound across is an F-type supergiant 1,300 light-years away. It makes
the perfect jumping-off point to find an object in

the sky celestial limbo.
Glance 1.5° due east of Arneb. Can you make out a

misty knot of four faint stars? That’s NGC 2017.

Lepus the Hare offers some less-explored celestial sights. Originally classified as an open cluster, we now know
that NGC 2017 is an asterism that happens to also

include the multiple-star system h3780. With most

At this time of binoculars, we can see that the system’s brightest star,

year, all eyes are at 6th magnitude, is framed by a tight triad of

on Orion, Taurus, 8th-magnitude attendants.

Canis Major, Gemini, and Lepus contains a single entry in Charles Messier’s

Auriga, with their bevy of famous catalog: M79, an out-of-the-way globular clus-

stellar and deep-sky trea- ter. To find it, bunny-hop 3° from Arneb southwestward

sures. But that leaves other to Beta Leporis (also known by the proper name Nihal),

constellations to pass by and then repeat the leap, continuing in the same direc-

unnoticed and underap- tion. Most globular clusters swarm around the center

preciated. This month and of our galaxy, placing them in our summer sky. But a

next, let’s explore the rest of few, like M79, lie in the opposite direction. M79 sits

the winter sky. 60,000 light-years from the galactic center, about 10,000

South of Orion’s knees, light-years farther than our solar system. Some believe

marked by Rigel (Beta [β] that this points to an extragalactic origin — that M79

Through binoculars, Orionis) and Saiph (Kappa was once affiliated with a tidally disrupted dwarf galaxy

M79 (NGC 1904), a [κ] Orionis), are a half-dozen or so fainter stars that known as the Canis Major Dwarf.
collection of 100,000 form the constellation Lepus the Hare. Through binoculars, M79 appears much like Messier
stars, appears as a
single, fuzzy star. Even though its brightest star shines no better than himself described it in December 1780, two months

ADAM BLOCK/NOAO/AURA/NSF magnitude 2.6, Lepus is apparent in suburban backyards after his contemporary, Pierre Méchain, discovered it:

if there is a good view to the south. Directly below the “Nebula without a star; the center bright; the nebulosity

imaginary line connecting Rigel and Saiph lie four of a little diffuse.” In reality, of course, M79 is a spherical

the Hare’s brightest stars, set in a distinctive trapezoid. collection of about 100,000 stars. You will find this

Beginning at the northernmost of the four and moving fuzzy little patch of light just northeast of a

clockwise, there’s Alpha (α), Beta (β), Gamma 5.5-magnitude star, SAO 170351.

(γ), and Delta (δ) Leporis. All fit comfortably Lastly, we come to a challenging treasure,

into a 7° field of view through binoculars. the tiny but colorful planetary nebula IC 418,
Of the four, Gamma will immediately This month better known as the Spirograph Nebula

catch your eye. That’s because it has a friend, and next, (thanks to a famous image from the Hubble
a 6th-magnitude star 97" to its north. The Space Telescope). I received a note last winter
4th-magnitude star you see by eye alone is let’s explore from reader Scott Harrington (no relation)
known as Gamma A, while its fainter com- the rest reminding me just how bright this planetary
panion is Gamma B. The Gamma system lies of the nebula is, and yet how few of us have ever

29 light-years away, with the stars separated winter sky. seen it. Although many sources list it as

from each other by an estimated 870 astro- photographic magnitude 10.7, it appears

nomical units — where 1 astronomical unit, much brighter by eye, bringing it well within

or AU, is the average distance between Earth the limits of most binoculars. IC 418 is some-

and the Sun. Together, they create one of the most strik- times called the Raspberry Nebula, for its prominent

ing binocular binaries in the entire sky. Each is bright pinkish color through giant backyard telescopes. With

enough and separated far enough from the other that most binoculars, however, it appears grayish, with pos-

any binocular can resolve them. When I study them sibly a blue or green tinge. Try it for yourself and let me

closely, Gamma A impresses me as yellow-white, know what you see.

BY PHIL although some report it as greenish. Gamma B is a Questions, comments, suggestions? Contact me
HARRINGTON subtle orange. Defocusing your binoculars slightly will through my website, philharrington.net. Until next
Phil is a longtime help enhance the delicate colors. month, remember that two eyes are better than one.
contributor to
Astronomy and the Next, shift your attention diagonally across the BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT
author of many books. Lepus trapezoid to Alpha Leporis, also known by the www.Astronomy.com/Harrington
proper name Arneb. The Hare’s brightest star, Arneb

WWW.ASTRONOMY.COM 59

[δ] Orionis), the most westerly of Orion’s Belt stars. This

OBSERVING BASICS 2nd-magnitude blue giant is accompanied by a much

fainter partner (magnitude 6.8, to be exact). Fortunately,

the lesser star is 56" away. Both were well seen at 70x.

Observe Orion A degree southwest of Alnitak (Zeta [ζ] Orionis), the
easternmost Belt star, is the multiple star Sigma (σ)
Orionis. In the 60mm refractor at 117x, Sigma was a

with ease triple: the 4th magnitude primary accompanied by two
6th-magnitude stars on one side separated from the main
star by 13" and 42". I then pointed my scope north to

Lambda (λ) Orionis, brightest of the triangle of stars that

Even a small scope reveals this timeless winter treat. forms Orion’s head. This eye-pleasing duo (magnitudes

3.5 and 5.5, separation 4.3") was split with 117x.

A year ago, I Turning to deep-sky objects, I made my way north-

N received an east towards Xi (ξ) and Nu (ν) Orionis, and the nearby
email from open cluster NGC 2169, sometimes called the 37 Cluster.
ξν

NGC 2169 ORION Joe McCoubrey, a NGC 2169 is comprised of two stellar groups — each
13-year-old astronomy forming one of the numbers. Just 7' in apparent diam-

λ π1 e n t h u s i a s t f r o m eter and comprised of a little more than a dozen stars,

π2 Bennett, Colorado, the 37 Cluster was best seen at 117x. Unfortunately, my
π3
α Betelgeuse γ π4 who asked me for a list scope was equipped with a standard star diagonal,
ω of the best winter sky which produced a mirror image of the 37.
targets for small tele-
From NGC 2169, I moved past Betelgeuse and trav-

scopes. The request eled an equal distance beyond to the reflection nebula,

E π5 reminded me that I M78. Similar in size to NGC 2169 and just 8th magni-
π6
hadn’t made a small- tude, it required a patient, minutes-long search with low
M78 Mintaka
scope voyage into the magnification (23x) before a rather faint puff ball
δ
ζε winter skies for years. appeared in the field. I tried higher magnifications, but
Alnitak σ
To remedy this over- 70x seemed to offer the best view.

θι¹ NGC 1981 sight, I decided to take I completed my journey at Orion’s Sword and the
M43 out my small scope constellation’s pièce de résistance: the Orion Nebula
(a 60mm refractor) and (M42/43). A magnification of 23x brought the entire
M42 τ β explore a classic winter Sword into view, from the loose open star cluster NGC
constellation: Orion. 1981 near the north end down to Iota (ι) Orionis and the
κ Rigel 5°

I began with Rigel. wide double star Struve 747 near the south. Since Iota is

Orion holds a plethora This 0.1 magnitude double and too close for a low-power split (the magni-
of beautiful celestial blue giant was a dazzling sight in the little scope. That’s tude 7.7 companion is 12.5" from the magnitude 2.8
sights you can explore, especially true at a magnification of 117x, where it flick- main star), I quickly switched to 117x for a clean split.
and many of them are

accessible using a ered like a diamond under somewhat turbulent skies. I The Orion Nebula was a magnificent sight in the little
small telescope.
used this high magnification (around the refractor, especially at 70x — a magnifica-
ASTRONOMY: ROEN KELLY

upper limit for a 60mm scope) in a vain If Rigel was tion that captured the expanse of the nebula
attempt to see Rigel’s 7th-magnitude while still resolving the four brightest mem-

companion, located about 10" away. a diamond, bers of its embedded multiple star Theta1
Theoretically, a 60mm refractor should be (θ¹), the Trapezium. It would take an entire
able to split double stars as close as 1.9", but Betelgeuse column to do justice to this region, as it’s one
that’s only if the component stars are rela- was sparkling of the finest deep-sky targets in the entire
tively bright and similar in magnitude. like a yellow- sky. (In fact, I did that in my February 2019

Rigel’s companion is 400 times fainter, so orange topaz. column, “Experience the Orion Nebula.”)

it’s easily lost in the bright star’s glare. I And although everything described in

chose to save Rigel and its partner for a night this article can be viewed through large-

with a steadier atmosphere. aperture instruments, there’s a sense of accomplishment

Next up was the red supergiant Betelgeuse. The color that comes with snagging a good look through a modest

contrast between ruddy Betelgeuse and blue-white Rigel instrument like a 60mm refractor. So, if you own one,

was striking. If Rigel was a diamond, Betelgeuse was take it out for a night under the Orion sky.

BY GLENN CHAPLE sparkling like a yellow-orange topaz. Betelgeuse wasn’t Questions, comments, or suggestions? Email me at
Glenn has been an alone, either. Just 20' to its south stood the pretty double [email protected]. Next month: more observer’s
avid observer since star Struve 817 (magnitudes 8.7 and 8.9, separation lists. Clear skies!
a friend showed 18.6"). This delicate little duo humbly shining next to
him Saturn through brash Betelgeuse was a captivating sight! BROWSE THE “OBSERVING BASICS” ARCHIVE
a small backyard AT www.Astronomy.com/Chaple
scope in 1963. Looking for more doubles, I moved to Mintaka (Delta

60 ASTRONOMY • FEBRUARY 2021

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WWW.ASTRONOMY.COM 61

A S K A S T R O Astronomy’s experts from around the globe answer your cosmic questions.

Some 520 light-years Galactic Spiral arms show the same structure
away lies AB Aurigae, traffic jam whether composed of billion-year-old
which has a twisted stars or million-year-old stars. This
planetary disk. The Q I WHAT CAUSES THE FORMATION indicates that the arms are the result of
spirals around AB OF SPIRAL ARMS IN GALAXIES? a persistent pattern of stars rather than
Aurigae are likely DO SPIRAL ARMS FORM IN OTHER particular stars causing the structures.
caused by baby FLATTENED GROUPS OF ORBITING
planets coalescing in OBJECTS, LIKE PLANETARY RINGS AND That pattern is caused by a density
the dust surrounding PROTOSTELLAR DISKS? (pressure) wave that spirals from the
the young star. ESO/ edge of the disk to the center and back
Robert Harrison out again, creating the visible spiral
BOCCALETTI ET AL. Albuquerque, New Mexico arms of the galaxy. Essentially, as stars
and gas move through the pattern, they
A I Spiral arms in galaxies can form by a combina- bunch up in the wave crests, like a
tion of processes. In a spiral galaxy, everything stellar traffic jam, and then eventually
orbits at the same speed, meaning stars and gas near break past the crest and continue on
the center of the galaxy complete an orbit in less time their orbit.
than objects farther out. This effect is referred to as
differential rotation. So, in the time it takes an inner Both planetary rings and protoplan-
star to complete one revolution around its galaxy, an etary disks can have density waves and
outer star might have only finished half a revolution. spiral structure. Planetary rings are
made of small amounts of debris
Differential rotation naturally generates spirals as the trapped in a particular orbit. Sometimes
galaxy rotates. Galaxies like the Milky Way have rotated they are perturbed by moons that cause waves.
a few dozen times — it typically takes 200 million years According to computer simulations, observed spirals
for the entire galaxy to complete a revolution. If in protostellar disks are from density waves driven by
differential rotation were the only process involved in planets forming in the disk.
generating spirals, we would expect to see many tightly
wrapped spiral arms, like a wound coil. But most spiral Debra Elmegreen
galaxies have only two to four main arms. Professor of Astronomy on the Maria Mitchell Chair, Vassar College,

Poughkeepsie, New York

Q I SINCE NEW HORIZONS’ FLYBY OF
ARROKOTH IN JANUARY 2019, IS
THE SPACECRAFT ZOOMING TOWARD A
NEW TARGET? IS NEW HORIZONS ABLE
TO SEARCH FOR PLANET NINE?

Douglas Kaupa
Council Bluffs, Iowa

A I New Horizons is healthy and routinely study-
ing the Kuiper Belt environment and Kuiper
Belt objects (KBOs) it passes in the distance. For the
next year or so, the New Horizons team is using the
largest telescopes on Earth — such as the Subaru
telescope in Hawaii — to find more KBO targets. From
there, we can determine if New Horizons has the fuel
to perform a flyby.

We should know the results of our first search by fall
or early winter 2020, and we will observe again using
ground-based telescopes between April and September
2021. If either search succeeds in finding a potential
target, we would seek NASA’s permission to burn our
engines to conduct another flyby.

I personally consider Pluto to be the solar system’s
ninth planet to honor its discoverer Clyde Tombaugh
and his contributions to planetary science. So, I call

62 ASTRONOMY • FEBRUARY 2021

from the center of the galaxy, suggesting it was kicked

WHERE NEW HORIZONS IS NOW out of the galactic center. SEND US YOUR
QUESTIONS
As to what happens to the rest of 3C186, the short
Send your
answer is that the galaxy will remain as it is. A galaxy astronomy questions
via email to askastro@
is held together by the collective mass of its stars, gas, astronomy.com, or
write to Ask Astro, P.O.
Uranus Neptune and dark matter, and any gravitational effects of the Box 1612, Waukesha,
WI 53187. Be sure
central SMBH are negligible with respect to that of the to tell us your
full name and where
whole galaxy. For example, the SMBH at the center of you live. Unfortunately,
we cannot answer all
Jupiter our own Milky Way — Sagittarius A* (Sgr A*) — has a questions submitted.
Saturn
Pluto mass only one-millionth the total mass of the galaxy. The galaxy 3C186 —
itself the likely result
Arrokoth So, Sgr A* only dominates the motions of the stars and of a previous galaxy
merger — hosted the
gas in a very small central volume and not of the galaxy merger of two super-
massive black holes.
as a whole. The resulting gravita-
tional waves are
When two galaxies merge, their SMBHs will eventually believed to have
“kicked out” the newly
KUIPER BE LT coalesce into a new SMBH. In the case of 3C186, this new created supermassive
black hole from the
New Horizons black hole likely received a “kick” from the gravitational center of the galaxy.

New Horizons is currently deep within the Kuiper Belt, about waves emitted during the SMBH merger, acquiring NASA, ESA, AND M. CHIABERGE
48 astronomical units (AU) from the Sun, where 1 AU is the (STSCI/ESA)
average Earth-Sun distance. After passing Arrokoth, New velocities up to several thousand miles per second.
Horizons is on the hunt for a new Kuiper Belt object to fly by.
As a result of this kick, 3C186’s SMBH’s orbit began
ASTRONOMY: ROEN KELLY
to oscillate around the galaxy’s core. Nearby stars and
Pluto planet nine. With regard to the hypothetical
object Konstantin Batygin and Michael E. Brown gas were pulled along with it, in principle creating
believe causes the perturbations of KBOs’ orbits, the
jury is still out on whether it is real. Scientists have observable effects such as distortions in the morphology
looked for such a planet for many years and have not
been able to find it. and dynamics of the galaxy. However, since the SMBH’s

While it would be fun to look for new planets with sphere of influence is very limited, the entire galaxy will
New Horizons, large telescopes on Earth do a much
better job than the smaller telescopes New Horizons is not suffer major disruptions, even if the black hole is
equipped with. New Horizons also has no internal
reaction wheels and relies on its thrusters to orient completely ejected.
itself, so slewing the spacecraft around to search for
planets would waste precious fuel we could use for But this does not mean that the overall influence of
another flyby farther out in the Kuiper Belt.
the central SMBH on the host galaxy is negligible! There
S. Alan Stern
are a number of extremely close relations between the
Principal Investigator for New Horizons,
Southwest Research Institute, Boulder, Colorado mass of the SMBH and the properties of its host galaxy,

known as scaling relations. These mean the host galaxy

and its SMBH essentially grow together. But, as we have

seen, this cannot be due to the gravitational influence

of the SMBH. There must be something else causing

this relationship.

Stefano Bianchi

Associate Professor, Università degli Studi Roma Tre, Rome, Italy

Q I WHAT WILL HAPPEN TO THE
STARS IN THE GALAXY 3C186,
NOW THAT THE CENTRAL SUPERMASSIVE
BLACK HOLE HAS BEEN EJECTED
FROM THE GALACTIC CENTER? WILL
THEY SLOWLY DRIFT APART, OR WILL
THEIR COLLECTIVE MASS HOLD THEM
TOGETHER FOR A WHILE?

Dennis Moore
Houston, Texas

A I Located 8 billion light-years away, the galaxy
3C186 is home to an extremely bright galactic
nucleus — the signature of an active supermassive black
hole (SMBH). But this SMBH is about 35,000 light-years

WWW.ASTRONOMY.COM 63

READER GALLERY

Cosmic portraits

1. HAWTHORNE’S A

The Scarlet Letter
(Sharpless 2–96) is an
emission nebula in the
constellation Cygnus the
Swan. Astronomers
suspect that it is part
of supernova remnant
SNR 65.2+05.7.
• Jerry Yesavage

2. AWAY IT GOES

An occultation is
the temporary
disappearance of a
celestial body due to the
passage of another in
front of it, from a certain
point of view. The Moon
occulted Mars on
August 9, 2020.
• Ricardo José Vas
Tolentino

3. BLUE BEAUTY

Abell 72 is a planetary
nebula in the
constellation Delphinus
the Dolphin. This
glowing shell of gas
expanding outward from
a dying Sun-like star
spans 2 light-years.
This image combines
18.6 hours of exposures.
• Douglas J. Struble

1

2 3

64 ASTRONOMY • FEBRUARY 2021

4. FULL CIRCLE
This 360° panorama shows the
entire sky above Black Canyon
of the Gunnison National Park
in Colorado. The two-row
composite has one row for the
sky and one for the landscape,
which was shot without tracking
before it was completely dark,
in order to retain detail. The
image includes the Milky Way
and lots of colorful airglow.
• Vince Farnsworth

5. WAGGING ITS TAIL
The tail of Comet C/2019 U6
(Lemmon) appears to touch
open cluster M41 in Canis Major
on May 27, 2020, from Tivoli —
Southern Sky Guest Farm in
Namibia. At the time, the comet
stood a mere 20° above the
horizon. • Gerald Rhemann

6. SOUTHERN BRILLIANCE
The Southern Pleiades goes by
several other names, including
Caldwell 102, IC 2602, Collinder
229, and the Theta Carinae

4 Cluster. But its resemblance to
the Pleiades (M45) makes “the
Southern Pleiades” the name
that resonates most with
observers. Because it glows
at magnitude 1.9, this cluster
is easy to spot without
optics. • Nicholas Clarke

7. FLASH FORWARD
The green flash happens when
long-wavelength light (red,
orange, yellow) from the setting
Sun is bent away from our eyes.
These three exposures were
captured a few seconds apart
March 29, 2020, from Siesta Key,
Florida. • Tom Fazekas

SEND YOUR IMAGES TO:
Astronomy Reader Gallery,
P.O. Box 1612, Waukesha,
WI 53187. Please include the
date and location of the
image and complete photo
data: telescope, camera,
filters, and exposures.

5 6 Submit images by email to
readergallery@
astronomy.com.

7

WWW.ASTRONOMY.COM 65

BREAKTHROUGH

HEAVY METAL STAR ATTRACTION

Globular cluster NGC 6441 doesn’t get a lot of respect from amateur astronomers. Maybe its location in southern Scorpius,
which keeps it low in the sky from midnorthern latitudes, tips the scales against it. And its great distance of roughly
40,000 light-years doesn’t help. Yet NGC 6441 stands out among the Milky Way’s approximately 150 globular clusters. It ranks
among our galaxy’s most massive and most luminous globulars, weighing some 1.6 million solar masses and shining with the
light of 600,000 Suns. It also contains more metals — astro-speak for elements heavier than helium — than most globulars.
Perhaps this stunning Hubble Space Telescope portrait will help NGC 6441 gain the respect it deserves. ESA/HUBBLE AND NASA/G. PIOTTO
66 ASTRONOMY • FEBRUARY 2021



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