BBC Sky at Night - September 2021

NORTH

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highlights
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sky guide

September 2021 BBC Sky at Night Magazine 51

SOUTH

MOONWATCH September’s top lunar feature to observe

Billy N ZD[LQJ JLEERXV SKDVH \RXŝOO KDYH WR ZDLW DERXW IRXU
hours for the Moon’s terminator to creep from Billy,
Type: Crater IDU HQRXJK ZHVW WR EHJLQ UHYHDOLQJ +DQVWHHQ 8QGHU
Size: 46km VXFK LOOXPLQDWLRQ WKH FUDWHUV ƅQG DQ HTXLYDOHQFH
Longitude/Latitude: Ō: Ō6 Hansteen’s intricate inner structures creating a
Age: Ś ELOOLRQ \HDUV FRPSOH[LW\ RI VKDGRZ ZKLFK LV D GHOLJKW WR REVHUYH
Best time to see: )RXU GD\V DIWHU ƅUVW
TXDUWHU 6HSWHPEHU RU WKUHH GD\V +RZHYHU DV WKH 6XQ EHJLQV WR FOLPE LQ WKH VN\ DV
DIWHU ODVW TXDUWHU 6HSWHPEHU seen from the location of this pair, sunlight falls more
Minimum equipment: PP WHOHVFRSH squarely onto the lunar surface and the lengths of
the shadows decrease. With fuller, high-angle
LOOXPLQDWLRQ +DQVWHHQ EHJLQV WR FDPRXƆDJH LWVHOI

ZHOO LQWR LWV KLJKODQG VXUURXQGLQJV +RZHYHU %LOO\ŝV

Located on the southern shore of 2FHDQXV GDUN ƆRRU Ś RQH RI WKH GDUNHVW UHJLRQV RQ WKH 0RRQŝV

3URFHOODUXP, crater %LOO\ may be only 46km in Earth-facing side

diameter but it has presence due to its dark, Billy’s dark floor is Ś FRPHV LQWR LWV
ODYD ƅOOHG ƆRRU 7R WKH QRUWK DQG VOLJKWO\ ZHVW RI own, remaining

Billy is 45km +DQVWHHQ a crater of similar size but one of the darkest SURPLQHQWO\ YLVLEOH
completely different appearance. Where Billy’s against its brighter

ƆRRU KDV EHHQ FRPSOHWHO\ VPRRWKHG RYHU E\ ODYD regions on the Moon’s surrounding
Hansteen’s remains faithful to the original impact HQYLURQPHQW

PETE LAWRENCE X 3 DQG DSSHDUV URXJK FRYHUHG LQ D VHULHV RI FRQFHQWULF %LOO\ŝV ƆRRU ORRNV
remarkably smooth,
Earth-facing sideULQJV LQƅOOHG ZLWK KLOOV

At times of oblique illumination, Billy’s 1.3km-high the rim simply

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ƆDW ODYD VXUIDFH DFWLQJ OLNH D VFUHHQ 'XULQJ WKH H[FHSW SRVVLEO\ WR WKH VRXWK ZKHUH DQ HOHYDWHG VKRUH

KDV KHOG WKH LQYDGLQJ ODYD DW ED\ 7ZR VPDOO FUDWHUOHWV

7KH FUDWHU %LOO\ VWDQGV can be seen in the southeast quadrant. Roughly
RXW EHFDXVH RI LWV 1.6km and 1.5km in diameter, like Billy itself, their

2&($186 GDUN ODYD ƅOOHG ƆRRU east-west dimensions are squashed due to
352&(//$580 foreshortening, as a result of where Billy appears

+DQVWHHQ to sit on the Moon’s globe as seen from Earth.

For those with large scopes or high-resolution

0RQV +DQVWHHQ /HWURQQH imaging setups, there’s a tiny craterlet in the
southwest quadrant perhaps just 10-20 metres in

diameter. Although far too small for Earth

REVHUYDWLRQ WKH EULJKW HMHFWD VXUURXQGLQJ WKH
%LOO\ craterlet is similar in size to the southeast quadrant

craterlets. The bright ejecta material contrasts well

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HOHYDWHG KLOO VLWV WR WKH QRUWK RI WKLV UHJLRQ DQG WKLV

too may be detectable under low light conditions.

,PPHGLDWHO\ QRUWK RI %LOO\ DQG UHYHDOHG DW WKH

same part of the Moon’s phase-cycle is the

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+DQVWHHQ. This looks like a bright, north-pointing

arrow, best seen when the terminator is nearby.

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*DVVHQGL part of the Moon. Located 320km to the southeast is
the 100km walled plain *DVVHQGL, most noted for

the complex rille (narrow channel) structures that

FULVV FURVV LWV ƆRRU ,Q FRQWUDVW NP WR WKH

east-northeast is 120km /HWURQQH DQRWKHU ODYD ƅOOHG

crater which has fared less well than Billy. Letronne

keeps the part of its rim running from the northwest,

0$5( +802580 through west, around south and up to the east, but
the remainder is missing, submerged beneath the

ƆRRU RI WKH 2FHDQXV 3URFHOODUXP.

52 BBC Sky at Night Magazine September 2021

COMETS AND ASTEROIDS

View asteroid 2 Pallas as it reaches a 11 Sep
opposition in Pisces, the Fishes 1 Sep 2 Pallas

0LQRU SODQHW 3DOODV LV DV LWV SUHƅ[ QXPEHU VXJJHVWV WKH VHFRQG g 21 Sep
PLQRU SODQHW GLVFRYHUHG ,WŝV RQH RI WKH ŜELJ IRXUŝ DVWHURLGV ZKLFK
LQFOXGHV &HUHV QRZ UH FODVVLƅHG DV D GZDUI SODQHW -XQR DQG PISCES
9HVWD 7KH\ ZHUH GLVFRYHUHG LQ FORVH SUR[LPLW\ WR RQH DQRWKHU
between 1 January 1801 and 29 March 1807. Amazingly, 5 Astraea h Circlet
ZDVQŝW GLVFRYHUHG XQWLO 'HFHPEHU EUHDNLQJ D ORQJ SHULRG
where it was thought that 1-4 were the only such objects. To date, 14 1 Oct
DURXQG RQH PLOOLRQ DVWHURLGV KDYH EHHQ REVHUYHG DQG UHFRUGHG HIP 113184
The four largest asteroids (in size order) are Ceres, Vesta, Pallas Neptune 90 AQUARIUS
DQG +\JLHD 7KH WKLUG GLVFRYHU\ -XQR LV WKH WK ODUJHVW h
2 Pallas is third largest with a mean diameter around 513km. 20
1 Sep 30 Sep q
3DOODVŝV GLVFRYHU\ LV DWWULEXWHG WR +HLQULFK 2OEHUV RQ 0DUFK
1802, but it was a close call. Charles Messier recorded it 23 years r
earlier while tracking a comet, but he thought it was a star and
LWV LGHQWLW\ UHPDLQHG KLGGHQ ,Q *LXVHSSH 3LD]]L GLVFRYHUHG s
&HUHV :KLOH LQLWLDOO\ EHOLHYLQJ LW WR EH D FRPHW LWV PRWLRQ ZDV s s
unlike any he’d seen before. After months being lost from sight,
&HUHV ZDV UHFRYHUHG E\ %DURQ YRQ =DFK DQG 2OEHUV ODWHU LQ Þ 6SRW DVWHURLG 3DOODV DV LW SDVVHV IURP 3LVFHV WR $TXDULXV
It was while attempting to relocate Ceres a few months later,
WKDW 2OEHUV IRXQG 3DOODV ZKLFK ZDV QHDUE\ LQ WKH VN\ Pallas reaches opposition on the 11th when it can be seen at
mag. +8.5 in Pisces, to the southwest of the faint Circlet asterism.
It spends much of the month in Pisces, skipping into Aquarius at
the end. Starting the month at mag. +8.8 and ending at mag. +8.9,
Pallas is an easy target for a small scope. It’s a B-type asteroid,
SDUW RI WKH & W\SH FODVV EXW KDYLQJ D VSHFWUDO ELDV WRZDUGV EOXH

STAR OF THE MONTH þ 7KH QDPH 'DELK FRPHV IURP WKH

$UDELF PHDQLQJ şWKH EXWFKHUŠ
7KH V\VWHP LV OLJKW\HDUV DZD\

Dabih, a western marker of Capricornus _
i Algedi
The constellation of is a true binary, its companion CAPRICORNUS
Capricornus, the Sea Goat a little closer than the 6.6 Dabih
looks like a misshapen triangle. arcminute separation of Jupiter f e
It’s not the easiest pattern to Algedi, at just 3.4 arcminutes. `
make out, but thanks to some In reality, the Dabih system is ba d o
planetary crowding it’s a little far more complex than it qr
easier to locate at present; VHHPV FRPSULVLQJ ƅYH VWDUV LQ Deneb Nashira l
both Jupiter and Saturn total. The brighter star shines Algiedi p /m
currently reside there. Two at mag. +3.1 and is designated
distinguishing features of the Beta1 (` ) or Beta (`) Capricorni g¡ k
main pattern are a pair of A. The dimmer component Saturn
middle-bright stars marking shines at mag. +6.1 and is M30 c
the east and west ends of this designated Beta (` ) or Beta s
down-pointing triangle. (`) Capricorni B. t
The pair at the western end,
nearest Saturn, are Algedi Beta Capricorni A is a triple K-type orange star, 35 times binary pair, the components
(Alpha (_) Capricorni) and system formed from a primary larger than our Sun. Ab has an being designated Ba and Bb.
Dabih (Beta (`) Capricorni). Aa and a binary pair Ab and apparent magnitude of +7.2 The separation of this pair is
Ab . The separation between and is a white B-type main larger at 3 arcseconds. Beta
To the naked eye, Algedi Aa and the Ab /Ab pair is tiny sequence dwarf. The Ab Capricorni Ba shines at
looks double, but this is at 0.05 arcseconds. Ab and component remains unseen. mag. +6.1 and appears white
nothing more than a line-of- Ab RUELW RQH DQRWKHU RYHU D in colour, an A0 giant star.
sight effect. In contrast, Dabih period of 8.7 days. Aa is a Beta Capricorni B, is also a

September 2021 BBC Sky at Night Magazine 53

BINOCULAR TOUR With Steve Tonkin

From Eddie’s Coaster to the Triangulum Galaxy, enjoy this month’s wide-field targets

o k

l 3 NGC 7686

Collinder 463 Caph NGC 7789

2 g ` m h NGC 7662
NGC 129 W
Eddie’s g f
Coaster NGC 225
ANDROMEDA
CASSIOPEIA a Schedar

M103 p d_ h PEGASUS

Segin Ruchbah c 5º Alpheratz
f¡ NGC 281 N _

NGC 654 b NGC 457 E c
NGC 663 r W d

Trumpler 3 1 e k S

IC 1805 e
l
IC 1027 Stock 2 4

M110 M31 m

Double cluster q

IC 1848 h M32
i
Collinder 33 r
Collinder 34 d Trumpler 2 q 51

/
+

b¡

a o p

PERSEUS e ` Mirach

NGC 1444 Almach a 5 6
_
NGC 752 Hockey M33
Mirfak Stick
M34
Melotte 20 56
hm

sg
b

1. Muscleman Cluster 3. Caroline’s Rose 5. The Hockey Stick
10x Start at Ruchbah (Delta (b) 15x You’ll find our next object, NGC 7789, 15x Identify the easy double star, 56
50 Cassiopeiae) and pan 6.5° to the 70 as its discoverer Caroline Herschel 70 Andromedae and, rising to the right.
east, where you’ll find a faint cluster of did in 1783, between Rho (l) and Sigma (m) you’ll see a straight-ish chain of 6th and
stars extending for more than 1°. This is Cassiopeiae. Don’t expect to be able to 7th magnitude stars, forming the Hockey
Stock 2, the Muscleman Cluster, which resolve any stars, even if you use averted Stick asterism more than 1.5° long, with 56
gets its name from the sparse pattern vision. Even in 15x70 binoculars it appears Andromedae at the lower end and open
of brighter stars that have the form of as a soft glow, about half the apparent cluster NGC 752 as a fuzzy ball. The
a stick man who is flexing his biceps in diameter of the Moon. With an age of a association is an optical illusion: at 1,300
bodybuilder pose. The Muscleman is billion years, Caroline’s Rose is unusually lightyears, NGC 752 is four times more
1,050 lightyears away. SEEN IT old for an open cluster. SEEN IT distant than 56 Andromedae. SEEN IT

PETE LAWRENCE X 3 2. Eddie’s Coaster 4. The Andromeda Galaxy, M31 6. The Triangulum Galaxy
10x Eddie’s Coaster is an asterism that is 10x If you can’t see it with your unaided 15x This low surface brightness galaxy
50 more obvious in 10x50 binoculars 50 eye, start with Mirach (Beta (`) 70 needs a dark sky. Return to Mirach
than just about anything else. Look 3° Andromedae) at one side of the field of and imagine a point that is diametrically
north of Gamma (a) Cassiopeiae, where view and Mu (μ) Andromedae at the other. opposite it from M31. The ghostly glow of
you will find this 3° long wave of 7th and Place Mu Andromedae where Mirach was, M33, the Triangulum Galaxy, may appear
8th magnitude stars, reminiscent of a and the elliptical Andromeda Galaxy, M31, only as a slight brightening of the sky,
roller coaster. It was discovered by the late will appear where Mu Andromedae was. even with averted vision. It is face on to us
West Country amateur astronomer, Eddie Notice the brighter glow of the galaxy’s and appears about the same size as the
Carpenter and listed in 2013. Cast around nucleus and see if you can identify the Moon. SEEN IT
the Milky Way, and you too may discover two companion galaxies, M32 and M110,
a pattern of interest. SEEN IT appearing as defocused stars. SEEN IT Tick the box when you’ve seen each one

54 BBC Sky at Night Magazine September 2021

THE SKY GUIDE CHALLENGE

How many galaxies can you spot that are bound to the Andromeda Galaxy, M31?

The Andromeda Galaxy, M31, lower surface brightness. It lies still well within reach of NGC 185’s brightness is more
becomes well placed in 37 arcminutes northeast of amateur equipment. concentrated towards its core
September. Good binoculars or M31’s core. and this makes it easier to see.
a small telescope also reveal Our charts show the Deep-sky photography can
two satellite galaxies, M32 and In theory, the next satellite location of both galaxies. Both be used to reveal a dark dust
M110 nearby. However, these galaxy in terms of brightness are really close to one another, feature in NGC 185, giving an
aren’t the only galaxies is Andromeda VIII, a dwarf just less than a degree apart. appearance not dissimilar to
gravitationally bound to M31. spheroidal galaxy discovered Visually, both can be seen a fainter version of M64, the
This month’s challenge is to in 2003. Its integrated through binoculars under Black Eye Galaxy.
hunt down some of the others. magnitude is +9.7 but it’s also dark-sky conditions but for
large at 45.0 x 10.0 arcminutes. the best views, apertures over If you fancy a real challenge,
There are actually quite a This spreads its light over a 250mm are recommended. of the many other faint
few, the latest count including large area giving it a low If you’re into imaging, a wide- satellites of M31, Andromeda
at least 32 entries. Many of surface brightness, explaining ƅHOG VKRW ZLWK ERWK JDOD[LHV LQ III (PGC 2121) is another low
WKHVH DUH IDLQW DQG GLIƅFXOW WR why it took so long to detect. the frame would work well. surface brightness target
discern but a number are Realistically, expect to record within amateur-imaging range.
within amateur range. M32 has Surface brightness is also sizes roughly half those stated. Using a star chart app, the
an integrated magnitude of low for NGC 185 and NGC 147, galaxy sits 5° south-southwest
DQG LV HDV\ WR ƅQG DV LW OLHV both located in neighbouring NGC 147 is the hardest. It’s of M31, one-third of the way
close to the M31, situated just Cassiopeia. With respective faint and elongated in shape. along a line from TYC 2274-
23 arcminutes south of the integrated magnitudes of A number of faint foreground 1298-1 (mag. +10.9) and TYC
core. M110 is of similar +10.1 and +10.5 respectively, stars appear clustered over the 2274-0735-1 (mag. +10.2).
integrated magnitude at +9.4, although their 11.7 x 10.0 and core of the galaxy, misleading It shines at mag. +13 and is
but is more spread out with a 13.2 x 7.8 arcminute sizes you into thinking you’re seeing 3.0 x 4.5 arcminutes in size.
present dim targets, they are something brighter than it is.

q HIP 1*&
k

/ &$66,23(,$
1*&

M $1'520('$
i

M110
M

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Mirach
HIP
HIP

PGC 2121 m

HIP 2942

/

Þ See if you can spot NGC 185 and NGC 147 north of the Andromeda Galaxy, and then the more tricky PGC 2121 to the south-southwest

September 2021 BBC Sky at Night Magazine 55

DEEP-SK Y TOUR Discover the irregular and spiral galaxies
within the Great Square of Pegasus asterism

1 NGC 14 arcminutes across, you’ll need a big scope to
The Great Square of Pegasus is a see this mag. +14.5 object. Much easier is
large distorted ‘square’ asterism NGC 7771, which lies 5.4 arcminutes to
the east-southeast of NGC 7769,
formed from Markab, Scheat with a brightness at mag. +12.3.
and Algenib in Pegasus (Alpha SEEN IT
(_)), Beta (`)) and Gamma (a)
Pegasi respectively) along 4 NGC 7625
with Alpheratz (Alpha NGC 7625 is
(_) Andromedae). another spiral

We’ll start with the located within the Great
faint but easy to locate Square’s boundary. This
irregular galaxy NGC 14. time the orientation
It has an apparent presents us with an
magnitude of +12.7, but almost circular object, 1.6
is diffuse. At a distance x 1.4 arcminutes across. It
of 47.1 million lightyears, shines at an integrated
it appears as little more magnitude of +11.9 and is
than a faint smudge. It’s believed to be around 81
located 1.25° northwest of million lightyears away.
Algenib and has an apparent Locate it via the southern
size of 2.0 x 1.3 arcminutes, the edge of the Great Square.
elongated dimension orientated Imagine the line from Markab to
in a north-northeast/south- Algenib; from a point a quarter of the
southwest direction. SEEN IT way along that line (starting at Markab),
head north for about one-eighth the length of
MICHAEL BREITE/STEFAN HEUTZ/WOLFGANG RIES/CCDGUIDE.COM, CHART BY PETE LAWRENCE 2 NGC 7814 Þ Spiral galaxy the line (about 2°) and you’ll be in the right area. A
Our next target sits 1.4° west-northwest of mag. +6.7 star sits 6.6 arcminutes east of the galaxy.
NGC 14, or if you had trouble with that NGC 7814 is A 250mm scope shows NGC 7625 as having a high
40 million surface brightness. SEEN IT
galaxy, 2.6° west-northwest of Algenib. It also sits 13 lightyears away
arcminutes southwest of mag. +7.2 star HIP 199. NGC 5 NGC 7741
7814 is a nice spiral galaxy around 40 million lightyears 1H[W ZH KHDG QRUWK WR ƅQG WKH EDUUHG VSLUDO
away. Shining with an integrated magnitude of +11.6, galaxy NGC 7741. The easiest locator is
it’s tilted to our line-of-sight to appear edge on to us:
a thin light strip with a central bulge. mag. +4.9, 78 Pegasi, itself located by looking
WZR ƅIWKV DORQJ WKH QRUWKHUQ HGJH RI WKH *UHDW
Smaller instruments show its elongation well, Square starting at Alpheratz. Once found, drop south
about 3 arcminutes in length oriented southeast- from the star by 3.2° to locate NGC 7741.
northwest with a 1 arcminute rough-textured core.
The core appears condensed and a bit asymmetric. The galaxy has an integrated magnitude of
Long-exposure images through large scopes reveal a +11.4, but its apparent size is large, at the extreme
dust lane running the galaxy’s length. SEEN IT measuring around 4.0 x 2.8 arcminutes, meaning its
surface brightness is low. A 250mm scope shows a
3 NGC 7769, NGC 7770 and NGC 7771 More 3.0 x 2.0 arcminute object, the faint glow marginally
NGC 7769 is a relatively bright face-on increasing in brightness towards its core. SEEN IT
spiral galaxy, located 1.1° north-northwest ONLINE
6 NGC 1 & 2
of mag. +5.0 Phi ( ) Pegasi. It has an integrated Print out this 2XU ƅQDO WDUJHWV PDUN WKH VWDUW RI WKH 1*&
magnitude of +12.1 and appears about 1 arcminute chart and take an catalogue. NGC 1 and 2 are two spiral galaxies
across. A 250mm instrument reveals a small automated Go-To
concentrated core with a faint, star-like nucleus. tour. See page 5 appearing close to one another in the northeast
for instructions. corner of the Great Square. NGC 1 is an intermediate
7ZR DGGLWLRQDO JDOD[LHV RFFXS\ WKH ƅHOG RI YLHZ spiral. It shines with an integrated magnitude around
The faintest by far is NGC 7770. Listed as 1.0 x 0.9 +13.0. Its surface brightness is low, approaching 14th
magnitude, but it has a bright concentrated core. The
This Deep-Sky Tour has been automated apparent diameter of NGC 1 is around 45 arcseconds.
ASCOM-enabled Go-To mounts can now
take you to this month’s targets at the NGC 2 lies 1.8 arcminutes further to the south. This
touch of a button, with our Deep-Sky Tour is hard to spot, its integrated brightness being around
ƅOH IRU WKH (47285 DSS )LQG LW RQOLQH the mag. +14.5 mark. SEEN IT

56 BBC Sky at Night Magazine September 2021

00h30m
00h00m
23h30m
23h00m
22h30m
+30° b 67
64

¡ 72 NGC 7457 d Matar NGC 7292 +30°
_ Jones 1 k
78 PEGASUS 32
Alpheratz
+25°
ANDROMEDA NGC 16 NGC 1 Scheat
`
NGC 2 6 5

NGC 214 PGC 1467 NGC 7741

+35° NGC 23

s 56 Sadal Bari
+ NGC 7339
o
p NGC 7332

NGC 7678 h

+20° NGC 7717 3NGC 7798 5º

r NGC 7771 NGC 7769 51 +20°

NGC 7770 2º

47 87 q 75 NGC 7550

NGC 57 4 NGC 7497

2 NGC 7625
1 NGC 7814
NGC 7454 NGC 7280

+15° Algenib NGC 14 _ NGC 7448 +15°

a NGC 7711 Markab
UGC 12613
Great Square
PISCES of Pegasus

00h30m
00h00m
23h30m
23h00m

22h30m
NGC 63 70 66 j
NGC 95 NGC 7479 Homam

+10° NGC 7742 77 c +10°
NGC 7743

AT A GL ANCE How the Sky Guide events will appear in September

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1
WT F S SMTWT F S SMTWT F S SMTWT F S SMTWT F

The Moon 17 Sep: 89%-lit waxing gibbous
Mercury Moon near Jupiter and Saturn
Venus
Mars 6 Sep: 1%-lit waning crescent Moon near Regulus
Jupiter
Saturn 9 Sep: 9% -lit waxing crescent Moon near Venus
Uranus
Neptune

Calendar
highlights

Moonwatch

Deep-Sky Tour

The Big Three The Moon (p46)
Galilean Satellite Events (p47)

Gruithuisen’s Lunar City (p47)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1
WT F S SMTWT F S SMTWT F S SMTWT F S SMTWT F

KEY

Observability IC Inferior conjunction Full Moon
Best viewed (Mercury & Venus only)
CHART BY PETE LAWRENCE Optimal Poor First
Sky brightness Daytime SC Superior conjunction quarter
during lunar phases Morning Last
twilight Evening Night OP Planet at opposition quarter
twilight
Meteor radiant peak New Moon

'DUN ƅUVW Light (full Dark (last Total darkness Planets in conjunction
quarter) Moon) quarter) (new Moon)

58 BBC Sky at Night Magazine September 2021

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Google’s astronomy Doodles

Ian Ridpath takes a look at the informative and amusing astronomy
illustrations that have graced Google searches over the years

A nyone who has ever individuals, among them a fair selection LW DV D YLVXDO ŜRXW RI RIƅFHŝ PHVVDJH 1HZ
searched the internet of astronomers, space missions and Doodles appear on an almost daily basis
will most likely have astronomical discoveries. now, created by a dedicated team.
encountered a Google
Doodle – a graphic or Doodles were born in 1998 when Larry All past Doodles are kept in an archive
animation at the top Page and Sergey Brin, Google’s founders, at www.google.com/doodles#archive.
of the Google search page. Doodles PRGLƅHG WKH VLWHŝV ORJR WR LQFOXGH WKH Of the 4,000-plus Doodles produced
celebrate anniversaries, events and symbol of the Burning Man festival, which to date, around 75 have astronomy
they’d gone to that week. They described connections. Here are some favourites…

Y Einstein

Many Doodles involve a visual play on
the distinctive Google logo. An amusing
H[DPSOH LV WKH ƅUVW DVWURQRPLFDOO\ UHODWHG
Doodle, released on 14 March 2003 to
commemorate Albert Einstein’s birthday.
Einstein’s famously unruly hair adorns the
ƅUVW OHWWHU ŜRŝ ZKLOH WKH ƅQDO OHWWHU ŜHŝ KDV
been co-opted to form part of his classic
equation E = mc2 (overlooking, for artistic
purposes, the fact that the ‘E’ in the
equation should be a capital).

V Women astronomers

Women astronomers have been celebrated in a number of Doodles, including the comet discoverer Caroline Herschel, depicted in
2016 on her 266th birthday. We see Caroline, her skirts billowing in the Slough breeze, bending down to look through a small refractor

perched uneasily on a table while a meteor
shower blazes through the skies above her.
There are two mistakes here that any reader
of this magazine should spot immediately.
Firstly, in reality she didn’t use a refractor, but
D VPDOO UHƆHFWRU PDGH IRU KHU E\ KHU EURWKHU
William Herschel; and secondly, meteors
aren’t the same thing as comets, which
was what she was famous for discovering.
Incidentally, William and his son John
Herschel remain ‘unDoodled’ so far.

ALL PICTUIRES: © GOOGLE A Doodle shower Z

The Perseids have been Doodled twice, in
2009 and 2014, the latter with a mood-
music soundtrack. But it’s the Doodle for
the Geminid meteor shower in 2018 (right)
WKDW , ƅQG PRVW HQFKDQWLQJ $ VOLGHVKRZ
of seven frames traces the stream of
debris left by the Geminids’ parent body,
the ’rock comet’ Phaethon, from its orbit
around the Sun to its annual encounter
with Earth. The stand-out feature is the
three-dimensional transitions against a
starry background as the slides advance.

60 BBC Sky at Night Magazine September 2021

Doodling space Z

Spacecraft and space missions feature
prominently as Doodles, among them
the 50th anniversary of Sputnik 1 (2007),
the 20th anniversary of the Hubble Space
7HOHVFRSH DQG 1HZ +RUL]RQVŝ
3OXWR Ɔ\E\ 9LVXDOO\ WKH PRVW
entertaining space Doodle to date was
of the Cassini spacecraft diving between
Saturn and its rings in April 2017 (right).
$UWLVW 1DWH 6ZLQHKDUW GHSLFWHG WKH SUREH
as an interplanetary paparazzo snapping
a series of shots before turning the
FDPHUD RQ LWVHOI IRU D VQHDN\ VHOƅH

V Apollo 11 For the 50th anniversary Google gave by a team of artists, researchers and
it the full Hollywood treatment with a audiovisual technicians, and a narration
Apollo 11’s lunar landing has been four-and-a half-minute video produced by Apollo 11 astronaut Michael Collins.

Doodled three times, in 2005, 2009 and

on its 50th anniversary in July 2019.

Z Into the V The Great Conjunction
black hole
The most recent astro-Doodle celebrated the Great Conjunction
On 10 April 2019 between Jupiter and Saturn last December, a once-in-800-years
astronomers released event that coincided with the winter solstice. In the animation,
WKH ƅUVW LPDJH RI D as Saturn swings past Jupiter it stops to doff its rings and
black hole taken by KLJK ƅYH WKH JLDQW SODQHW ZKLOH (DUWK EHORZ MXPSV IRU MR\
the Event Horizon 7KH 'RRGOH FDPH LQ WZR YHUVLRQV RQH IRU 1RUWKHUQ +HPLVSKHUH
7HOHVFRSH $UWLVW 1DWH viewers in which the Google logo was layered with snow, and
Swinehart (by now one for the Southern Hemisphere without snow.
our favourite astro-
Doodler) was already Ian Ridpath is a veteran populariser of
sketching ideas on astronomy. His books include the Collins
his way to work that Stars and Planets Guide, Collins Gem
morning, and later Stars and The Monthly Sky Guide,
that same day his all in print for over 30 years. Find him
animated Doodle at www.ianridpath.com
went live on Google’s
home page. In the September 2021 BBC Sky at Night Magazine 61
Doodle, the black hole
ƅUVW VXFNV LQ VWDUV
then the logo and
ƅQDOO\ WKH SKRWRJUDSK
itself, leaving inky
blackness. It’s a
tremendous tribute to
the imagination and
skill of the Doodlers.

© NIKHEF The location for the vast Einstein Telescope
could either be in the border region between
Belgium, Germany and the Netherlands,
or on the Italian island of Sardinia

62 BBC Sky at Night Magazine September 2021

The next step ILLUSTRATION
in gravitational
wave astronomy

Deep underground, the Einstein Telescope will monitor
the vibrations caused by gravitational waves from

colliding black holes, as Govert Schilling discovers

September 2021 BBC Sky at Night Magazine 63

The Einstein Telescope will pick upBRIGHTSTARS/ISTOCK/GETTY IMAGES X 3, VIRGO COLLABORATION,
gravitational waves caused by theSOARES-SANTOS ET AL AND DES COLLABORATION
energy released by black hole mergers
ILLUSTRATION
The most sensitive instrument in the “Our target is to
history of astronomy is going to be detect colliding
built in deep underground caverns and black holes
tunnels, a few hundred metres beneath throughout the
Earth’s surface. It may sound crazy, whole observable
but it’s true. The Einstein Telescope Universe.”
(ET) isn’t going to collect light photons and won’t – Michele Punturo
provide us with stunning images of nebulae and
galaxies. Instead, the almost €2bn–facility will Sixty years after his death, in 2015, Einstein was
UHJLVWHU JUDYLWDWLRQDO ZDYHV WKH LQƅQLWHVLPDO ULSSOHV proven right on the existence of gravitational waves,
in spacetime that propagate through the Universe but wrong on their non-detectability. Indeed, the two
at the speed of light as a result of the collisions highly sensitive detectors of the Laser Interferometer
and mergers of ultra-compact neutron stars and Gravitational-Wave Observatory (LIGO) registered
gluttonous black holes. the spacetime ripples of two colliding black holes
DW D GLVWDQFH RI ELOOLRQ OLJKW\HDUV 6LQFH WKDW ƅUVW
The telescope will form a giant equilateral triangle, discovery, both the US-based LIGO and the European
measuring 10km on each side. Powerful beams Virgo detector in Italy have observed dozens of
of laser light will travel up and down these arms, events, including tell-tale signals from colliding
bouncing off mirrors to gauge the length of the neutron stars, smash-ups of black holes and neutron
arms to see if they change by even a fraction the stars, and black holes with unexpected masses
width of an atomic nucleus. When such a change – maybe a result of earlier mergers.
does occur, it could mean a gravitational wave has
SDVVHG WKURXJK EULHƆ\ ZDUSLQJ WKH VSDFH DURXQG “Being able to learn more about these fascinating
the detector. “Our target is to detect colliding black objects is just incredible,” says theoretical
holes throughout the whole observable Universe,” astrophysicist Samaya Nissanke of the University
says Michele Punturo, co-chair of the international of Amsterdam. “The observations have had an
ET steering committee. HQRUPRXV LPSDFW RQ D ZLGH YDULHW\ RI VFLHQWLƅF ƅHOGV
including astronomy, physics, cosmology and general
*UDYLWDWLRQDO ZDYHV ZHUH ƅUVW GHVFULEHG RYHU D relativity. And what strikes me most is how fast we’ve
century ago by Albert Einstein. His general theory of grown completely used to actually observing black
relativity implied that spacetime could bend, warp, hole mergers. It’s amazing.”
expand or contract, like a four-dimensional rubber
sheet. Einstein also predicted that accelerating
masses create tiny undulations in the very fabric of
spacetime, alternately stretching and compressing
everything on their paths. However, even the
largest masses and the strongest accelerations
would produce gravitational waves with amplitudes
much smaller than an atomic nucleus. Einstein was
convinced they would never be detected.

64 BBC Sky at Night Magazine September 2021

3. Light bounces back and 2. Light hits beam splitter
forth hundreds of times and is sent off in two
different directions
1. Laser emits light
3. Light bounces back and
forth hundreds of times

4. The laser beams 5. A photodetector looks for a
are recombined signal, indicating the length
of the beam has changed

How does an interferometer work?

Merging light creates an ‘interference’ pattern, which can be analysed

Gravitational waves are detected with times between two mirrors (known as test If gravitational waves from space sweep
sensitive interferometers. A coherent masses) at the near and far ends of a vast over Earth, the lengths of the two detector
laser beam – meaning that the crests and kilometres-long vacuum tunnel. arms are subject to periodic variations.
troughs of all light waves are in sync – is Depending on the direction of arrival of
split in two by a beam splitter. Half of the The beams are then brought back these waves, variations in one arm won’t
laser light passes right through this together again going towards a match those in the second. As a result,
semi-permeable mirror, while the other photodetector. However, they are the combined laser waves no longer
half is reflected at right angles. Next, both normally arranged such that the troughs cancel each other out, and the detector
laser beams are reflected hundreds of of one light wave perfectly meet the crests will register a rapid flickering signal.
of another, cancelling out the signal.

GW170817: a view taken between … and the same view which will be much more sensitive than either LIGO
0.5–1.5 days after the merger of taken over 14 days or Virgo. Reaching out to distances 10 times as large,
a black hole and neutron star… after the merger the instrument will yield a thousand-fold increase
in the number of gravitational-wave events, as
N N volume goes up in proportion to distance cubed. “It’s
E E phenomenal,” she says. “The Einstein Telescope will
be able to detect many thousands of events per year.”
Þ Composite So far, only one gravitational-wave event (known
as GW170817, due to the merger of a black hole Going underground
images of and a neutron star) has also been observed by
GW170817 – a regular telescopes, but Nissanke, who is an expert This will only be possible through a whole set of
gravitational LQ WKLV QHZ ƅHOG RI PXOWL PHVVHQJHU DVWURQRP\ different improvements, explains Sheila Rowan,
wave event caused – meaning she studies the Universe using methods director of the Institute for Gravitational Research
by the merger other than just electromagnetic radiation – isn’t at the University of Glasgow. “The instrument will
of a black hole concerned about the lack of more detections with be built underground to diminish seismic noise,” she
and neutron star electromagnetic counterparts. “We were lucky in the says. “Some of the core components of the detector
– as captured case of GW170817,” she says. “It’s not easy, but soon ZLOO EH FRROHG WR Ō& DERYH DEVROXWH ]HUR %HFDXVH
by DECam, the enough, we’ll be getting more sensitive detectors, of these low temperatures, the mirrors need to be
Dark Energy better ‘sky localisations’, and more powerful sky made out of ultra-pure crystalline silicon instead
Survey Camera surveys. It will happen again.” of more regular glass or quartz. We’re also reaching
at Cerro Tololo out to lower-frequency waves,” which increases the
Inter-American Nissanke looks forward to the Einstein Telescope, instrument’s ability to detect in-spiralling binary
Observatory (CTIO) black holes at an earlier stage. Last but not least,
each of the three arms of the Einstein Telescope
will be 10km long, greatly increasing the sensitivity
compared to LIGO’s arm length of just 4km.

(DFK /,*2 DQG 9LUJR GHWHFWRU LV ƅWWHG ZLWK MXVW
one interferometer, located where the two arms
of the L-shaped detector meet. But the triangle-
shaped Einstein Telescope can hold an interferometer >

September 2021 BBC Sky at Night Magazine 65

A multitude of gravitational
wave detectors

A roundup of the interferometer
projects around the world

The US Laser Interferometer Gravitational-wave Observatory LISA (Laser InterferometerILLUSTRATION
(LIGO) consists of two identical detection facilities with 4km- 6SDFH $QWHQQD ZLOO EH WKH ƅUVW
long arms: one in Hanford, Washington, and the other in space-based mission to attempt
Livingston, Louisiana. The slightly smaller European Virgo the detection of gravitational waves
detector, with 3km–arms, is located near Pisa, Italy. In early
2020, the underground Japanese Kamioka Gravitational-wave technologies for its future Laser Interferometer Space Antenna
detector (KAGRA) came online, also with 3km arms. (LISA), due to be launched in the 2030s. LISA will consist of three
free-flying spacecraft, millions of kilometres apart; they are the
Apart from LIGO, Virgo and KAGRA, a smaller experiment vertices of a huge triangular gravitational-wave detector that
known as GEO600 is located near Hanover, Germany, but this has a similar design to the planned Einstein Telescope, but
facility is mainly used to test and qualify novel detection operating at much lower frequencies. Japan and China are also
technologies – it is too small to detect all but the most powerful preparing space-based detectors, known as DECi-hertz
gravitational waves. Meanwhile, US and Indian physicists are Interferometer Gravitational-wave Observatory (DECIGO) and
teaming up to build LIGO India, working with spare parts from TianQin, respectively.
LIGO. It is expected to be completed later this decade.

In 2016, using their LISA Pathfinder space probe, the European
Space Agency (ESA) successfully demonstrated the necessary

> at each of the three vertices. In fact, it will hold 2022,” says Stefan Hild of Maastricht University in the þ An artist’s
two interferometers at each vertex, looking for Netherlands, the leader of the construction effort.
gravitational waves of lower and higher frequencies, impression of
as the lower the frequency the larger the mass of the (7 3DWKƅQGHU LV EHLQJ EXLOW LQ D IRUPHU QHZVSDSHU the inside of the
source. The Einstein Telescope’s multi-interferometer printing plant that has been converted into a Einstein Telescope
setup will also make it possible to study the high-quality 1,000-square-metre clean room with gives a sense of
polarisation of the spacetime ripples, providing useful D FP WKLFN ƆRRU VXSSRUWHG E\ FRQFUHWH SLOHV its colossal scale
information about how the black holes were spinning measuring 6m-long and 30cm in diameter. With
as they collided. DUP OHQJWKV RI MXVW P RU VR (7 3DWKƅQGHU ZRQŝW
be able to actually detect gravitational waves, but
Partners in science most components of the testbed facility are fully
functional. “Over the next months, we will be building
Punturo notes that the current design of the Einstein quite a lot of things,” says Hild, who received a
Telescope is still rather preliminary. It could change in
the future, perhaps in response to the plans for
an American counterpart, known as the Cosmic
Explorer, which is still at an earlier stage of
development. “No, we don’t call it a competitor,”
he says. “We are partners in science, and the best
science will be achieved by mutual cooperation
between various facilities.” The same is already
very much true for LIGO and Virgo (and other
gravitational-wave detectors).

There’s no doubt, however, that many new
technologies will have to be incorporated in the
Einstein Telescope. That’s why scientists are
FRQVWUXFWLQJ WKH Ų P (7 3DWKƅQGHU Ś D WHVWEHG
for cryogenic components, silicon mirrors, novel
suspension mechanisms and new types of lasers.
The scale the detectors will be working on are so
small that quantum mechanics will start having an
effect, so they also need to trial smart measurement
techniques that will diminish the effect of the
Heisenberg uncertainty principle (which concerns
WKH GLIƅFXOWO\ RI PHDVXULQJ WKH SRVLWLRQ DQG
momentum of a particle at the same time). “We
H[SHFW (7 3DWKƅQGHU WR EH XS DQG UXQQLQJ LQ ODWH
ESA, © NIKHEF X 2, © NIKHEF/KEES HUYSER,
ILLUSTRATION

66 BBC Sky at Night Magazine September 2021

CENTRAL FACILITY

COMPUTING CENTRE

DETECTOR STATION

END
STATION

TUNNEL: 5m LENGTH: 10km

ILLUSTRATION The proposed design of the Einstein
7HOHVFRSH ZKLFK FXUUHQWO\ KDV D
budget forecast of around €2bn

ILLUSTRATION density. “Humans are noisy,” says Punturo.
This summer, the European Strategy Forum
Þ ESA’s ET European Research Council Advanced Grant of over
€2m for developing new detection methods. on Research Infrastructures (ESFRI) included the
3DWKƅQGHU IDFLOLW\ Einstein Telescope in the plans of its 2021 Roadmap,
in Maastricht will be Finding a location underscoring the importance of the new facility for
D SURWRW\SH IRU WKH European science. After the site has been selected
Einstein Telescope Maastricht, in the Netherlands, is also close to one of DQG WKH ƅQDO GHVLJQ KDV EHHQ DSSURYHG FRQVWUXFWLRQ
the two candidate locations for the full-scale Einstein of the Einstein Telescope would commence in
Govert Schilling Telescope: the underground facility could possibly be $FFRUGLQJ WR 3XQWXUR WKH ƅUVW SUHOLPLQDU\
is the author of built beneath the tripoint of the Netherlands, Belgium measurements could be made in the early 2030s,
Ripples in Spacetime and Germany. The other candidate site is located in while the start of full operations is anticipated in
(Harvard University WKH QRUWKHDVW RI WKH ,WDOLDQ LVODQG RI 6DUGLQLD $ ƅQDO 2035. “It will be a precision machine for black hole
Press, 2017) decision is not expected before 2024 or 2025. “The and neutron star mergers that are relatively nearby,”
term ‘best place’ is a very complex one,” explains says Punturo, “and a discovery machine for the
Punturo. “It involves not only science, technology, and distant and early Universe. We may even detect
geology, but also politics and logistics.” gravitational waves from primordial black hole
collisions that happened during the cosmic Dark
Both sites are known for their low level of $JHV EHIRUH WKH IRUPDWLRQ RI WKH YHU\ ƅUVW VWDUV
seismicity (even minute tremors could disturb the and galaxies.”
measurements), but Sardinia has a low population
In 2034, the European Space Agency also plans to
launch its Laser Interferometer Space Antenna (LISA),
a space-based gravitational wave detector (see box,
opposite). LISA operates at a much lower frequency,
enabling the detection of merging supermassive
black holes in the cores of distant galaxies. Indeed,
the two facilities will be very complementary in
opening up a new window on the Universe. “Together,
WKH\ ZLOO KRSHIXOO\ ƅQG D ORW RI PLVVLQJ SDUWV RI WKH
giant cosmic jigsaw puzzle,” says Nissanke. “It’s just
mind-blowing to imagine how astronomy will look
20 years from now.”

September 2021 BBC Sky at Night Magazine 67

STOCKTREK IMAGES, INC./ALAMY STOCK PHOTO

< Algol, the famous variable star in the

constellation of Perseus, takes its name from
the Arabic word meaning ‘head of the demon’

Late summer

VARIABLES
Observing variable stars is a great way for amateur
astronomers to aid professional research. Paul G Abel
is your guide to making accurate observations

A casual look at the night sky gives intrinsic variables and extrinsic variables. Intrinsic
the impression that the stars are variables are stars whose changes in magnitude
constant and unchanging. While it’s are caused by physical processes within the star
true that many stars remain fairly itself. For example, many red giants (such as
constant over the course of a human Betelgeuse (Alpha (_) Orionis) or Mira) shrink and
lifetime, there’s a large number expand over a period of months – as the surface
of stars that change quite rapidly, sometimes in a of the star expands, they become fainter; when it
matter of hours. contracts it becomes brighter.

The ancient Egyptians knew that the star Algol Eruptive variables, another example, are the
(Beta (`) Persei) in Perseus changed in brightness, result of violent changes on the surface of the star:
but it wasn’t until 1638 when Johannes Holwarda ODUJH ƆDUH DFWLYLW\ IRU LQVWDQFH FDQ FDXVH D VWDU WR
discovered that the apparent magnitude of the red brighten by six magnitudes. More dramatic examples
giant star Mira (Omicron (k Ceti) in the constellation include the novae and supernovae.
of Cetus, the Whale varied over a period of about
11 months. Eventually, other stars with similar Outside influences
behaviour were discovered and, before long, a new
area of astronomy arrived: the study of variable stars. Extrinsic variables vary due to physical interactions
with a nearby companion star. For example, the red
Today, variable stars play an important role in giant star SS Cygni has a white dwarf companion
stellar astrophysics – they provide an essential that pulls material off the main star. This material
laboratory in which we can test our models of stellar forms an accretion disc and over time, instabilities
evolution, from bloated red giants at the end of their in the disc change its viscosity, which alters the
lives to binary stars caught in fatal gravitational temperature and allows more material to be
ballets. Nevertheless, variable star observing is compacted into the disc. The end result is that
straightforward and surprisingly rewarding. It requires the accretion disc can become very bright – it’s
little more than binoculars or a small telescope, some capable of going from mag. +12.0 to mag. +8.0 in a
charts and a notebook. just few days. This system is an example of a dwarf
nova (quite different from a supernova, which is a
But why do stars vary? Fundamentally, variable VXSHUPDVVLYH VWDUŝV ƅQDO PRPHQWV >
stars can be broken down into two categories:

September 2021 BBC Sky at Night Magazine 69

SS Cygni is an extrinsic
variable, due to a nearby
white dwarf drawing material
away from the red giant
NASA/CXC/M.WEISS/SCIENCE PHOTO LIBRARYAUL ABEL,
CHARTS BY PETE LAWRENCE, PETE LAWRENCE X 2> In contrast, Algol varies in brightness due to itsVSHQG WLPH FKHFNLQJ WKDW WKH VWDUV LQ WKH ƅHOG RI þ Record your
companion passing in front of and behind the star, view match up with those on your chart. It’s probably
ILLUSTRATIONwhich makes it an eclipsing binary system.best to use a low-power eyepiece to begin with – thisobservations of
should allow you to match the stars you can see with the variable stars
Getting started those on your chart. you observe in
a logbook – this
:KHQ VHWWLQJ RXW WR REVHUYH YDULDEOH VWDUV WKH ƅUVW :KHQ \RXŝYH ORFDWHG DQG FRQƅUPHG \RXU YDULDEOH log is of SS Cygni
thing you need to do is to choose some. It’s a good ƅQG D VXLWDEOH FRPSDULVRQ VWDU LGHDOO\ RI VLPLODU
idea to start with some variables that are easy to brightness) and record how much brighter or fainter
ORFDWH Ś WKH ƅYH YDULDEOHV OLVWHG RQ SDJH DQG the variable is compared to it. The Pogson step
DUH JRRG H[DPSOHV 6RPH QHHG WR EH REVHUYHG method is good way to do this. You estimate the
more frequently than others – pulsating Mira-type magnitude of a variable star with the help of a
stars should only be observed once a week (as their FRPSDULVRQ VWDU XVLQJ VWHSV RI RI D PDJQLWXGH >
changes are slow), while eruptive or dwarf novae can
be observed on any clear night.

Variable star observing is ideal for observers with
binoculars or small telescopes. In fact, you shouldn’t
XVH DQ\WKLQJ ODUJHU WKDQ D LQFK PP WHOHVFRSH
for objects brighter than the 8th magnitude. Also be
careful of bias; red giants can appear brighter than
they actually are.

To begin your observations you’ll need to print
off a suitable variable star chart (see ‘Equipment
DQG UHVRXUFHVŝ RQ SDJH 6HHLQJ FRQGLWLRQV DUHQŝW
too important for variable stars, but you’ll want
the sky to be free of haze and to avoid observing
in strong moonlight. It’s a good idea to record your
observations in a logbook – record the date, time (in
UT – Universal Time), your magnitude estimate and
the chart sequence. You should also record the size
and type of telescope used.

2QFH \RX KDYH WKH YDULDEOH VWDU LQ WKH ƅHOG RI
your telescope or binoculars, you’ll need to estimate
its brightness. Don’t rush this – it’s really important
WKDW \RX LGHQWLI\ WKH YDULDEOH VWDU LQ WKH ƅHOG VR

70 BBC Sky at Night Magazine September 2021

Five late-summer variables

These examples are an ideal test-bed for your powers of observation

SS Cygni Z RA 21h 42m 42.9s S dec +43° 35' 10" (2000.0)

SS Cygni is a dwarf novae that resides in the 75 CYGNUS
constellation of Cygnus, the Swan, not far from the
nice double star 75 Cygni. When it’s quiescent (in a 7.6
state of inactivity), the star is approximately mag.
+12.0, but during an outburst it can brighten to about 8.5
mag. +8.0. SS Cygni undergoes these outbursts every
seven to eight weeks, so should be checked 11.4
out whenever there’s a clear night. 12.8

S 10.9 SS 9.6 E

W 9.9
11.9

12.3

10.3 9.1

SS Cygni

SS Cygni is located to the Telescope view N Field 1° x 1°
northeast of 75 Cygni
S dec +32° 54' 51" (2000.0) Y Chi Cygni
RA 19h 50m 33.9s
CYGNUS Located fairly close to Eta (¡) Cygni at the base
8.2 of the ‘Northern Cross’ asterism in Cygnus, Chi
9.2 (r) Cygni is a splendid red giant of the Mira type.
10.5 Over a period of about 400 days, Chi Cygni can
9.6 get as bright as mag. +3.5, before fading down to
a minimum around mag. +14. Chi Cygni is throwing
Wr off material into space, material that will eventually
form a planetary nebula. Aim to observe this star
10.3 once a week, if possible.

S

E

10.0 8.8
8.4 Chi Cygni

V1765 N Field 1° x 1° Chi Cygni can reach a
brightness of mag. +3.5
Telescope view
continued over the page X

September 2021 BBC Sky at Night Magazine 71

RA 03h 08m 10.1s N dec +40° 57' 20" (2000.0) RA 14h 29m 45.3s S dec +38° 51' 41" (2000.0)

2.7 BOÖTES
b
_

CASSIOPEIA

h

r Double cluster

2.9 a 8.1

1.8 _ 6.3 a
Mirfak
9.9 9.2
b 11.0 V

E g 3.8 a WW 9.6 11.4 E
2.1 10.6

¡ Algol M34

` ANDROMEDA

PERSEUS l 3.0 ` 7.2

c 3.4 _ 11.7 7.5
8.8
Pleiades TRIANGULUM Telescope view
8.7
Naked eye view ARIES _ Field 3° x 3°
S Field 38° x 38° N

U Algol U V Bootis

This is an example of an eclipsing binary system – Algol (Beta Another beautiful red giant, in Boötes, the Herdsman, close to
(`) Persei) is, in fact, composed of three stars: Beta Persei Aa1, Seginus (Gamma (a) Boötes). This star ranges from around mag.
Beta Persei Aa2 and the fainter Beta Persei Ab. It’s the two hot +7.0 to mag. +12.0 over a period of 258 days. Studies of the light
primary stars, Beta Persei Aa1 and Beta Persei Aa2, that eclipse curve suggest that there’s a secondary period of about 137 days,
each other and these eclipses take approximately 10 hours. and during the early part of the 20th century the overall light
Algol is usually around mag. +2.1, but every 2.9 days it drops curve was somewhat different (the star could be evolving away
to mag. +3.4. Try to observe it each clear night. from being a Mira-type star). Aim to observe it once a week.

R Scuti Z RA 18h 47m 29.0s N dec -05° 42' 18"

This yellow supergiant star is an example of a RV AQUILA 7
Tauri variable. It lies close to both Beta (`) Scuti and 8
the splendid Wild Duck Cluster, M11. The light curve 14 5.4
for this star is quite remarkable and shows periods 15 4.2 ` 8.4
of deep minima and unusual ‘stand-stills’, during 6.5
which its magnitude is constant for long periods of h 6.2 R SCUTUM
time. It’s thought that the dynamics of the star are
responsible, but there are many questions yet to be E V 12 4.8 M11 7.0 8.8
answered. Observe this star every chance you get. d EW
7.9
N Beta Cygni

W

R Scuti 7.3 S V453 _
M11 7.1 ¡
CHARTS BY PETE LAWRENCE
Find R Scuti to the M26 b
south of Beta Cygni
Binocular view S Field 8° x 8°
and west of M11

72 BBC Sky at Night Magazine September 2021

Equipment and resources

The essential kit you need for a productive night Þ Keep your night
of observing variable stars
vision preserved with
a red-light torch

Red light Astronomical Association (britastro. (in Universal Time), the chart sequence
org/vss) or the American Association of of the chart containing your comparison
An essential bit of kit! White light will Variable Star Observers (aavso.org). The stars, your estimate and the deduced
destroy your night vision and distort charts provided by these organisations magnitude of your star.
your magnitude estimates. Your eyes have carefully chosen comparison stars
must be dark adapted when you’re listed. Each chart has its own name A laminator
observing variables. (called a chart sequence). Magnitudes of
the comparison stars on AAVSO charts Laminating your charts will protect
Binoculars or a small telescope have no decimal point (which could them against dew and save you from
be confused as a star), while the printing a new chart every clear night.
There are a few naked-eye variables, magnitudes of stars on BAA charts are
but many hundreds are in the range given by letters to prevent bias. Online resources
of binoculars or a small telescope.
A selection of low- to medium-power A notebook Check out the BAA at britastro.org/vss
eyepieces is also useful. and AAVSO at aavso.org. Both
You’ll need to keep a record of your organisations allow you to download
Comparison charts magnitude estimates for each variable charts and generate light curves. There’s
star you observe. You should include: the help with different aspects of variable
It’s essential that the correct star charts name of the variable star, the date, time star observing, and you can upload your
are used for magnitude estimates. observations as you make them.
You can get charts from the British

Paul G Abel is the > So if your comparison star is mag. +10.3 and you frequently the star is varying (its period), and the
director of the think the variable is four-tenths brighter, you’d long-term study of light curves often provides hints
British Astronomical record it as ‘103 – 4’. This notation means that of other astrophysical processes that may be at work.
Association’s the comparison star is of mag. +10.3 and that you From the light curve of SS Cygni we know that there
Mercury and Venus estimate the variable to be about four-tenths brighter are two types of brightening, one that lasts less than
section. He’s also a (by convention, you exclude the decimal point). Based 12 days and others that last a lot longer.
theoretical physicist on this estimate, the variable has a magnitude of
at the University +9.9, as mag. +9.9 is 0.4 times brighter than mag. +10.3. It’s not uncommon for variables to throw up some
of Leicester surprises – they may get brighter or fainter than
If instead the variable was about six-tenths fainter, usual (Betelgeuse for example). Alternatively, they
you’d record ‘103+6’ and the deduced magnitude might remain quiescent for unusually long periods
would be +10.9. You can repeat this with other of time (the star R Coronae Borealis experienced
FRPSDULVRQ VWDUV LQ WKH ƅHOG WR JHW WZR RU WKUHH an unusually long period where it was very faint,
estimates and then take an average. You can dipping below mag. +14; at the time of writing it’s
ƅQG PRUH GHWDLOHG H[SODQDWLRQV RI WKH 3RJVRQ about mag. +6.0). All this tells astronomers that
step method on the American Association of something interesting is going on and adds to our
Variable Star Observers (AAVSO) and the theories of stellar evolution, or our understanding of
British Astronomical Association (BAA) websites accretion theory.
(aavso.org and britastro.org/vss), along with an
alternative, known as the Fractional Step method. Finally, it’s really important to report your
observations to the Variable Star Section of the BAA
Light curves or the AAVSO. Both organisations allow you to enter
your observations via an online form. The BAA in
Repeating your observations over time will give particular has been collecting amateur observations
you a series of magnitudes for the variable star of variable stars since 1890 and has a number of
and when you plot these on a graph (with dates on pro-am collaborations.
the horizontal axis and apparent magnitudes on
the vertical) the result is called a light curve. These Your long-term observations of variable stars are
are unique to each star, although similar types of part of an invaluable resource – most professional
variables have similar light curves. This is the main telescopes are engaged in large fundamental
aim of variable star observation and the more observing campaigns, and it would be quite
observers that contribute magnitudes for a given impossible to use them for long-term measurements
star, the more accurate the light curves become. You of the many thousands of variable stars known to
can plot light curves from your observations on the exist. By observing and recording variables, you’ll
AAVSO or the BAA websites. be contributing to the only long-term narrative
professional astronomers have of these objects, and
The light curve is key to understanding a variable’s doing so will help us answer the many questions that
behaviour. From this, we can determine how remain regarding the private lives of these stars.

September 2021 BBC Sky at Night Magazine 73

Practical astronomy projects for every level of expertise

DIY ASTRONOMY

FAMILY Make a 3D model of our nearest stars

FRIENDLY

PROJECT Get to know the distances between the Sun and its closest stellar neighbours

Show nearby stars Mary McIntyre z coordinates for each star as seen from Earth – the
in relation to the is an outreach x-axis is horizontal and the y-axis is vertical, with the
orbital plane of astronomer and Sun’s location represented by the point at which the
our Solar System teacher of two axes intersect. The z value represents each star’s
astrophotography distance above or below the plane of the Solar System.
F or this fun project we create a three- These values are in parsecs, with 1 parsec = 3.26
dimensional model that shows where the lightyears. We multiplied each value by our scaling
nearest 20 stars to our Solar System are factor, 1 parsec = 3cm applied in all directions, so
located. It places the Sun at its centre the model’s diameter covers 30 parsecs. Don’t
and gives you a unique perspective of our worry if this sounds complex; we’ve done the maths
nearby stellar neighbourhood. It doesn’t in a downloadable spreadsheet (see below for
just consider the distances of the stars, but gives their LQVWUXFWLRQV 7KH VWDUV DUH QXPEHUHUG WR IRU HDVH
real coordinates relative to the orbital plane of the of reference and the z values have had 4mm added
Solar System, which allows you to see exactly where to allow for the thickness of the cardboard disc.
the nearby stars lie relative to our Sun. We achieve
all this by using basic materials and the project is We mapped the x and y FRRUGLQDWHV RQWR WKH ƆDW
packed with learning opportunities for your family. GLVF ƅUVW DQG WKHQ XVHG EDUEHFXH VNHZHUV SDLQWHG
The stars are colour-coded depending on their EODFN WULPPHG WR WKH FRUUHFW OHQJWK WR UHSUHVHQW
spectral class, so you can discuss the differences the z coordinates. The stars, represented by coloured
between the classes and explain that although EHDGV DOVR SDLQWHG EHIRUHKDQG ZHUH DWWDFKHG WR
76 per cent of stars in our stellar neighbourhood are the skewer ends. Our stars in this project are not to
Ŝ0 FODVVŝ ZLWK D WHPSHUDWXUH XS WR Ō& PRVW DUH scale – if they were, they would be microscopic!
too faint to be seen with the naked eye.
We displayed the model on a simple stand so it is
Placing the stars aligned with the plane of our Solar System, but you
could easily adapt it to be a hanging model.
7R ZRUN RXW WKH SODFHPHQW IRU WKH VWDUV ZH ƅUVW
downloaded the Astronomy Nexus star database MORE ONLINE
from www.astronexus.com/hyg. We imported it
into Excel and sorted the stars by distance and then Download a spreadsheet of stellar neighbourhood
selected the nearest 20. For the stars that are double measurements. See page 5 for instructions.
or triple star systems, we represented the brightest
ALL PICTURES: MARY MCINTYRE star of that system. The database gives you x, y and What you’ll need

X A piece of sturdy cardboard, measuring 30cm x 30cm, plus a piece
of graph paper the same size – we stuck two pieces of A4 graph
paper together.

X Use 21 wooden barbecue skewers; 20 of 3mm diameter for the stars
and a thicker one of 4mm diameter for the stand and the Sun.

X You’ll also need 20 small black buttons, which will be glued to the
ends of the skewers to act as stops for each star (excluding the Sun).

X Find 21 beads that fit onto the pointed ends of the skewers; you’ll
need 12 red, four orange, three yellow (including one for the Sun),
one pale yellow and one white.

X A small, sturdy box to use as a base for the stand; ours measured
7cm x 8.5cm x 4cm.

74 BBC Sky at Night Magazine September 2021

Step by step

Step 1 Step 2

Draw and cut out a 30cm-diameter circle from the sturdy card. Make a duplicate circle from graph paper; from the centre
This is the base plane of the Solar System and where the star point, draw x (horizontal) and y (vertical) axes in a cross shape,
skewers will be added later. Next, paint it black – we used spray extending 15cm each way. Using the values in our downloadable
paint, but you can use any water-based paint. table, mark the x and y values for each star and label them.

Step 3 Step 4

Place the graph paper over the cardboard circle. Using a small Using the z values from the table, cut the star skewers to length
awl or push-pin, poke a hole through the paper and into the card to represent the distance above or below the plane of the Solar
at the centre point and everywhere you plotted a point on the System, labelling them 1 to 20 as you go. Use a hot glue gun and a
graph. Label the holes 1 to 20 with a pencil. black glue stick to glue a button onto the cut end of each skewer.

Step 5 Step 6

Poke the numbered skewers through the corresponding Cut the larger skewer to 26cm; push the pointed end into the
numbered hole, remembering that a negative z value should centre hole and attach the final yellow bead to the top for the
be pointing downwards and a positive value points up. Add the Sun. Make a small hole in the base box and poke the skewer into
correctly coloured bead to each skewer, securing it with glue. it. A blob of Blu Tak inside will help to hold it more securely.

September 2021 BBC Sky at Night Magazine 75

Take the perfect astrophoto with our step-by-step guide

ASTROPHOTOGRAPHY

CAPTURE

Imaging an occultation

Capture two lunar occultations of naked-eye stars, on the mornings of 2 and 3 September

while accurate timings for the disappearance and
reappearance of the star help us determine its shape.
Similarly, accurate timings of a lunar occultation can
KHOS XV WR UHƅQH WKH VKDSH RI WKH 0RRQŝV OLPE

If you have a stills camera, taking a photo of a star
near to the edge of the Moon is straightforward. With
the star in frame and the camera lens or attached
WHOHVFRSH IRFXVHG LWŝV SRVVLEOH WR JHW D VHTXHQFH RI
shots showing the Moon moving towards it or away.

:LWK D SODQHWDU\ FDPHUD VHWXS LWŝV SRVVLEOH WR
obtain an accurate timing for the event. Many control
software options will record detailed logs of capture
sessions, including the start and end time, and frame
interval. Using a captured video of an occultation
disappearance or reappearance will permit accurate
timings of the key events to a fair degree of accuracy.

A similar result may be obtained with the movie
mode on a DSLR, although lower sensitivity and a
less accurate camera clock may lessen the precision.

ALL PICTURES: PETE LAWRENCE The term occultation describes when Þ With a stills Reappearing act
one body is hidden or occulted by
another. This could be Jupiter passing camera you can The events on the 2nd and 3rd occur in the early
in front of one of its four Galilean take a series of hours, the Moon being in its waning crescent phase;
moons, or an asteroid passing in front shots of a star near its bright edge will be doing the hiding, the stars
of a star. A total eclipse of the Sun is the bright edge of reappearing from behind the dark limb. A bright edge
technically an occultation of the Sun by the Moon. the Moon, which brings exposure into consideration; set the sensitivity
A more commonly witnessed type of occultation FDQ KHOS UHƅQH WKH RI \RXU FDPHUD WRR KLJK DQG \RXŝOO KDYH D GRPLQDQW
occurs when the Moon moves in front of a star, hiding VKDSH RI LWV SURƅOH bright over-exposed Moon in your shots. The
it from view and then revealing it again as the Moon reappearance is much easier to deal with in this
tracks east against the starry background. Two Pete Lawrence is an respect, but of course the issue here is whether you
well-timed lunar occultations of naked-eye stars in expert astro imager KDYH WKH ULJKW SDUW RI WKH 0RRQŝV OLPE LQ WKH ƅHOG RI
Gemini occur on the mornings of 2 and 3 September, and a presenter on YLHZ DQG LI \RX DUH UHFRUGLQJ \RXU PRYLH VHTXHQFH DW
providing a great opportunity to view these events. The Sky at Night the right time to catch the star reappearing.

Timing occultation disappearances and > For more on lunar occultation events, see page 46
reappearances can help provide information about
the occulting body. Asteroid occultations have a Recommended equipment: a telescope on a driven
degree of imprecision to them due to tiny unknowns mount, a planetary camera
in the position and shape of the asteroid. Showing
WKDW DQ DVWHURLG RFFXOWDWLRQ LV YLVLEOH IURP D VSHFLƅF
Send your images to:
ORFDWLRQ RQ (DUWK KHOSV UHƅQH WKH DVWHURLGŝV SRVLWLRQ [email protected]

76 BBC Sky at Night Magazine September 2021

Step by step

STEP 1 STEP 2

Select the type of camera; a DSLR or other type of stills camera The longer the effective focal length, the narrower the field of
can deliver a decent result, but an accurate timing can be tricky. view. DSLRs will also typically offer larger fields than high
The occultation disappearance on 2 September takes place at frame-rate cameras. Decide whether you want to image with all the
low altitude and may be distorted by seeing. A high frame rate Moon’s surface in view or to zoom into the region of interest. Wider
device overcomes seeing effects, and has better timing accuracy. field setups take the pressure off for the reappearance event.

STEP 3 STEP 4

If you plan on Accurate focus is essential for occultation images. Fortunately,
making a timed for lunar occultations of bright stars, you have two easy focus
event recording, it’s targets – the star which is being occulted and the Moon’s
essential that the surface. Take your time over focusing, and revisit the task
DSLR’s clock, or the several times before disappearance as well as reappearance.
onboard clock of
a computer being
used to control a
high frame rate
camera, has been
synchronised to an
internet time
server. Time server
examples include
time.google.com
and time.windows.
com. A computer’s
operating system
normally offers
synchronisation
options via its ‘Date
and time’ settings.

✗ ✓✗

STEP 5 STEP 6

Ensure the object being occulted is visible in your images. This Individual frames can be extracted from an AVI movie sequence
can be done prior to disappearance, and a note of the settings using freeware such as VirtualDub (virtualdub.org), or PIPP
should be made to ensure the same values are used for (bit.ly/3x2vCJ3). In VirtualDub it’s possible to step through the
reappearance. Exposures should be kept less than 0.5s in length, sequence, frame-by-frame, copying frames to the clipboard
and balanced with as low a gain (ISO) as possible to reduce noise. (Ctrl-1) to load in an image editor.

September 2021 BBC Sky at Night Magazine 77

Expert processing tips to enhance your astrophotos

ASTROPHOTOGRAPHY

PROCESSING

How stacking can transform deep-sky images

Use image-processing software to bring out the hidden details of galaxy targets

Before: our RAW galaxies image
may look reasonable, but it can
be transformed with stacking

ALL PICTURES: DAVE EAGLE A W ƅUVW JODQFH D VLQJOH 5$: LPDJH FDQ Þ After: the stacked VWDFNHG LPDJH IRU IXUWKHU SURFHVVLQJ %\ VWDFNLQJ
look quite good – just like our photo LPDJHV OLNH WKLV \RXŝUH DGGLQJ WKH GDWD WRJHWKHU
RI 0 DQG 0 DERYH ULJKW %XW and processed UHGXFLQJ QRLVH XQZDQWHG DUWHIDFWV PDNLQJ LW ORRN
SUREOHPV ZLOO VRRQ FRPH WR OLJKW LI image of M81 (left) D ORW VPRRWKHU DQG HQDEOLQJ \RX WR WDNH SRVW
\RX WULHG WR SURFHVV LW IXUWKHU \RXŝG and M82 teases processing much further. This makes it easier to tease
TXLFNO\ ƅQG LW ZRXOG QRW FRQWDLQ out detail from the RXW KLGGHQ GHWDLO ZLWKLQ WKH LPDJH VR LW ORRNV LWV EHVW
enough data or depth, and the image would start to famous galaxy
GHWHULRUDWH 7KH ZD\ WR JHW URXQG WKLV SUREOHP Ś DQG pair in Ursa Minor Everything’s covered
DFKLHYH D ULFKHU SLFWXUH TXDOLW\ RQ IDLQW GHHS VN\
REMHFWV Ś LV WR VWDFN D QXPEHU RI LPDJHV WRJHWKHU Dave Eagle is an $IƅQLW\ 3KRWR WDNHV FDUH RI WKH ZKROH MRE RI VWDFNLQJ
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images into the stack to remove camera defects. planetarium Ŝ$VWURSKRWRJUDSK\ 6WDFNLQJ 3HUVRQDŝ IURP WKH PHQX
,Q WKLV DUWLFOH ZHŝUH JRLQJ WR ORRN DW KRZ WKLV FDQ EH operator and writer EDU &OLFN RQ Ŝ)LOH ! 1HZ $VWURSKRWRJUDSK\ 6WDFNŝ DQG
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includes a selection of useful stacking tools. RSHQ GLVSOD\LQJ D EODFN LPDJH 2Q WKH ULJKW KDQG
side of the window there are three levels of ‘Studio
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<RX FDQ VWDFN PRQR DQG FRORXU 5$: LPDJH ƅOHV
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VHOHFW WKH LPDJHV WKDW QHHG WR EH VWDFNHG FOLFN WKH

78 BBC Sky at Night Magazine September 2021

Ŝ$GGŝ EXWWRQ ZLWKLQ WKH Ŝ)LOHVŝ SDQHO 7KH GHIDXOW 3 QUICK TIPS
VHWWLQJ LV WR VWDFN Ŝ/LJKWŝ IUDPHV LI WKLV KDV EHHQ
changed, make sure that ‘Light’ is selected from the 1. The ‘Sigma Clipping’ stack mode helps to
GURS GRZQ PHQX VHH 6FUHHQVKRW eliminate aircraft and satellite trails.

1H[W FOLFN WKH Ŝ$GG )LOHVŝ EXWWRQ EURZVH WR WKH 2. $ VLQJOH ),76 ƅOH FDQ EH RSHQHG DQG VWDFNHG
IROGHU ZKHUH WKH LPDJHV \RX ZDQW WR VWDFN DUH on itself, for direct viewing or further processing
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GLVSOD\HG DV D VWDFN RQ WKH ULJKW KDQG VLGH RI WKH 3. The ‘Levels Adjustment’ and ‘Curves
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Þ Screenshot 1: stacking. If one is under par,
\RX FDQ VHOHFW WKH ƅOH E\
Within the clicking on it and then delete it
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September 2021 BBC Sky at Night Magazine 79

Your best photos submitted to the magazine this month More

ASTROPHOTOGRAPHY ONLINE

GALLERY A gallery containing

these and more

of your images

U The Sun’s sunflower Equipment: ZWO ASI174MM camera, PHOTO
William Optics GT81 refractor, DayStar OF THE
Alex Dean, Nottingham, 6 June 2021 Quark Chromosphere eyepiece, Celestron MONTH
CGEM mount
Alex says: “As soon as I Exposure: 4,000 frames at 10ms imaging, so with the right equipment it
realised that you can take Software: FireCapture, AutoStakkert! shouldn’t be too much of a change. Imaging
amazing images of our closest ImPPG (Image Post-Processor) LQ WKH PRUQLQJ DQG RYHU ƅHOGV KDV SURYHQ WR
star, I was completely hooked. be the least disruptive atmospherically. I use
It isn’t an easy subject to Alex’s top tips: “Apart from being a daytime a high frame rate mono camera so I can
image by far, but the results speak for activity, solar imaging is similar to planetary take 3,000–4,000 frames at around 10ms.
themselves. This is an image of AR2829,
one of several new active regions we can Once you have used AutoStakkert! for
see now the Sun is waking up from its period stacking, a great program to use for editing
of inactivity.” is ImPPG. Of course, never, ever look at the
Sun directly through a telescope.”

80 BBC Sky at Night Magazine September 2021

U The Whirlpool Galaxy

Kasra Karimi, Aylesbury, 18–19 April 2021
Kasra says: “I often drive out of the city to escape London’s light
pollution, camp and set up my telescope, even if it’s in the middle
of winter.”
Equipment: ZWO ASI 6200MC camera, TS-Optics 130mm
apo triplet, Sky-Watcher EQ6-R Pro mount Exposure: 75x 300”
Software: PixInsight, Photoshop

V The Leo Triplet

Jared Bowens, Clarksdale, Missouri, US, 27 March–23 April 2021
Jared says: “This was taken from my backyard observatory in
Missouri, where I’m lucky to have exceptionally dark skies.”
Equipment: Canon 60D DSLR, Orion 8-inch Newtonian
astrograph, Celestron AVX mount Exposure: 15.8h total
Software: PixInsight, Photoshop

U Noctilucent clouds

Hannah Rochford, Gower, 4 June 2021
Hannah says: “I’ve never seen [NLCs] before
and I couldn’t believe how beautiful they
are! It was around 11:45pm and they came
out of nowhere on a very clear night.”
Equipment: Canon 5D Mk II DSLR,

Sigma 150–600mm lens Exposure: ISO 500, f/5, 10”
Software: Photoshop

September 2021 BBC Sky at Night Magazine 81

Y The Pelican
Nebula

Ian Phillips, Weston-super-
Mare, 12 June 2021

Ian says: “This was
only my second
time using my
new Esprit 120ED.
Opportunities
were at a premium, thanks to
the short hours of darkness and
only two nights of clear skies in
two months.”
Equipment: ZWO ASI2600MC
Pro camera, Sky-Watcher Esprit
120ED refractor, Sky-Watcher
EQ6 Pro mount Exposure:
24x 5’ Software: PixInsight

Jupiter and
Galilean moons V

Paul Sparham, Leatherhead,
Surrey, 6 May 2018

Paul says: “I was
interested in your
article ‘A beginner’s
guide to planetary
imaging’ (June
issue 2021, p60), particularly
how you can use just a humble
smartphone. This setup can still
yield good results.”
Equipment: iPhone 5S, Orion
XT6 Dobsonian Exposure: 1,500
frames, with best 500 stacked
Software: AutoStakkert!, GIMP

82 BBC Sky at Night Magazine September 2021

The Rosette
Nebula Z

Tony McAvoy, Camborne,
Cornwall, December 2020
to January 2021

Tony says: “I’ve
spent hours trying
to master the art
of post-processing
with PixInsight.
It seems to be paying off.”

Equipment: QSI 583WSG
camera, William Optics GT81
refractor, Sky-Watcher HEQ5 Pro
mount Exposure: Ha 10h, OIII 8h,
SII 8h Software: SGPro, PixInsight

V The Veil Nebulae

Matthew Clough, Selby, North Yorkshire, 23 June 2021

Matthew says: “For processing, I used a
bi-colour channel combination and the
lightness curve to tease out the details
of the nebulosity.”

Equipment: ZWO ASI 294MC Pro camera,
William Optics RedCat 51 refractor, Sky-Watcher HEQ5
Pro mount Exposure: 31x 120” Software: PixInsight,
$IƅQLW\ 3KRWR

U Eclipse and the ISS

Antoine Thibault, Pontarlier, France, 10 June 2021

Antoine says: “After a two-hour drive and delays at the border
IRU &29,' FKHFNV , PDQDJHG WR UHDFK P\ VSRW LQ D FHUHDO ƅHOG
I missed the start of the eclipse, but I was on time to catch the
ISS transiting the Sun – it took less than a second.”

Equipment: Canon R5 mirrorless camera, Astro-Physics 130mm
refractor, Astro-Physics mount Exposure: ISO 100, 1/8000” Software: Photoshop

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September 2021 BBC Sky at Night Magazine 83

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Find out more about how we test equipment at
www.skyatnightmagazine.com/scoring-categories

86

An eyepiece-free telescope?
We put Unistellar’s innovative
eVscope eQuinox to the test

@THESHED/PHOTOSTUDIO HOW WE RATE PLUS: Books on the big cosmological
questions and the Space Race, plus a
(DFK SURGXFW ZH UHYLHZ LV UDWHG IRU SHUIRUPDQFH LQ ƅYH FDWHJRULHV roundup of essential astronomy gear
+HUHŝV ZKDW WKH UDWLQJV PHDQ

+++++ Outstanding +++++ Very good
+++++ Good +++++ Average +++++ Poor/avoid

September 2021 BBC Sky at Night Magazine 85

Our experts review the latest kit

FIRST LIGHT

Unistellar eVscope eQuinox

A smart, eyepiece-free telescope that offers light pollution-beating views of the deep sky

WORDS: JAMIE CARTER

VITAL STATS W ould you consider buying a ground-based optical telescopes used by
telescope that doesn’t have professional astronomers.
• Price £2,599 an eyepiece? On the face
(plus £59 of it, Unistellar’s eVscope Everything the eQuinox does is accessed through
shipping) eQuinox appears to challenge Unistellar’s app, so to view the sky with it you need a
conventional wisdom by not tablet or smartphone; up to 10 of these can be linked
• Optics 114mm including one, so we were keen to put it to the test. to the telescope via its Wi-Fi network. Your device
(4.5-inch) receives the images the scope generates, which are
reflector When Go-To telescopes arrived 20 years ago they refreshed every few seconds.
were hugely divisive; amateurs who had spent years
• Focal length learning their way around the sky felt cheated that :KLOH WKH DYHUDJH LQFK UHƆHFWRU ZLOO JLYH \RX
450mm, f/4 anyone could now access the same deep-sky gems disappointing deep-sky views of galaxies, globulars
LQVWDQWO\ %XW LWŝV QRZ UDUH WR ƅQG D WHOHVFRSH ZLWKRXW and nebulae from urban areas, the eQuinox’s
• Sensor Sony Go-To capability – and the hobby has blossomed. image-processing power can counter the effects of
Exmor IMX224 light pollution. The Unistellar app also asks if you’re in
The Unistellar eVscope eQuinox is the latest a city, a suburb or the countryside. Armed with that
• Mount version of the ‘smart’ digital telescope and is just as knowledge, it tweaks the in-app list of recommended
Motorised innovative. Like the original eVscope from 2020, the objects, relegating any that are likely to succumb to
single-arm, H9VFRSH H4XLQR[ LV D LQFK I UHƆHFWRU WKDW light pollution beyond the eQuinox’s capability. The
altaz, Go-To comes with a camera sensor that tracks and stacks limit in stellar magnitude that’s visible with the
images in real-time to produce rich-colour views of eVScope is +18.0 for dark skies, but still a whopping
• Power In-built deep-sky objects. In that respect, it’s just like the +16.0 for urban areas. >
lithium-ion
rechargeable Look, no eyepiece!
(12-hour)
@THESHED/PHOTOSTUDIO X 2, UNISTELLAR.COM X 2 battery The lack of an eyepiece on the eQuinox takes a little
getting used to. To focus images, instead of using an
• Tripod eyepiece and the focusing knob at the base of the
Aluminium, tube as on the original eVscope, you view the image
adjustable on a tablet and use the Bahtinov mask inside the dust
height cap. Clicked into place across the telescope’s tube
and with the eVscope pointed at a bright star, you
• Ports USB-C then manually tweak the focusing knob until spikes
for power, of light streaming through the mask’s three
and USB-A distinctive cut-outs intersect as shown in the app
for charging a view (see right).
smartphone
The eQuinox can also be manually focused just
• App control as well using the Moon, but therein lies a distinct
Unistellar disadvantage of having no eyepiece; the eQuinox’s
app for magnification is fixed at a field of view of 30
smartphones arcminutes. So you can never quite get the whole of
the Moon in view. But by removing the electronic
• Weight 9kg eyepiece Unistellar has given this telescope two
• Supplier hours’ extra run-time compared to the original
eVscope. Given that some deep-sky objects, and
Unistellar SAS certainly citizen-science tasks, benefit hugely from
• Email long observations, that’s a worthy improvement.

contact@
unistellar
optics.com
• www.unistellar
optics.com

Þ Focus is achieved in the Unistellar app by using a

Bhatinov mask and a focusing knob at the tube’s base

86 BBC Sky at Night Magazine September 2021

SCALE Optical tube

Mount The mirror and sensor are inside a tube
that measures 65cm long and 23cm wide.
The L-shaped altaz mount The design incorporates a 114mm (4.5-inch)
contains the motor, which diameter mirror with a focal length of
moves the telescope into 450mm (17.7 inches), which gives a focal
position and then accurately ratio of f/4. Light is focused directly onto
tracks objects. Inside the mount a Sony Exmor IMX224 sensor in a spider
are also the built-in lithium-ion vane on the front end.
battery and the on-board
computer. It features 64GB Connections
storage, four times more than
the original eVscope. There’s an on/off switch that glows blue
when switched on. The built-in battery pack
Tripod is recharged via USB-C, which you can do
using any portable battery. There’s also a
The tripod is designed for the USB-A slot on the side so you can recharge
eQuinox; the tube mounts on a smartphone or tablet.
a ring at the top and is secured
by two screws. The three-part September 2021 BBC Sky at Night Magazine 87
legs can stretch from 59cm to
heights of 133cm when fully
extended. The tripod weighs
2.2kg and is very sturdy.

FIRST LIGHT Dust cap

KIT TO ADD > With the eQuinox trained on The dust cap that sits on
the Whirlpool Galaxy, M51, you the front of the telescope’s
tube is there to keep it
1. A portable can watch as lanes of stars clean, but it’s got the added
battery and resolve: successive images bonus of containing a
USB-C cable add to the detail, clarity and Bahtinov mask. When
clicked into place on the
2. eVscope brightness every few seconds. front of the tube, the mask
can be used to focus on
backpack The time it takes to gather a star while using the
Unistellar app.
3. Twitter app, enough light to capture an
,Q VHFRQGV
for sharing object at its best depends on the eQuinox
reveals a clear
images in the object, sky transparency view of M27,
the Dumbbell
real-time and light pollution. Nebula…

For example, the Ring

Nebula, M57, looked wonderfully bright and colourful

after just 24 seconds. M51 was similarly impactful; its

JDODFWLF DUPV JDLQLQJ FRORXU DQG GHƅQLWLRQ WKH ORQJHU

the eVscope was left to track and stack. Meanwhile,

globular clusters – including M10, M13 and M71 – take

only a few seconds to impress.

@THESHED/PHOTOSTUDIO, JAMIE CARTER X 2 A view for sharing VERDICT +++++ Þ …and a view
+++++
While the images produced by the eQuinox are ideal Build & design +++++ of the Whirlpool
for viewing, sharing and learning (there are optional Ease of use +++++ Galaxy, M51,
overlays of info), they do fall short of those that can Features +++++ shows impressive
be produced with an astrophoto-grade scope on an Go-To/tracking accuracy ++++ GHƅQLWLRQ ,Q
equatorial mount under a dark sky, over many hours. Imaging quality addition, the
7KDW VDLG D ƅUPZDUH XSGDWH LVVXHG GXULQJ WKLV UHYLHZ OVERALL Unistellar app can
increased resolution from 1.2MP (1,120 x 1,120 pixels) to display overlays of
a much more impressive 5MP (2,240 x 2,240 pixels). facts about targets

Gain, exposure time and brightness can all be
WZHDNHG DQG FDSWXUHG LPDJHV DUH VDYHG DV 31* ƅOHV
to a smartphone or tablet, with only RAW data left
on the telescope. Regular uploading to Unistellar’s
servers is also recommended.

The eQuinox is extremely simple to set up and
although its Autonomous Field Detection software
makes initial alignment easy, it’s fastest when the
VFRSH KDV ƅUVW EHHQ PDQXDOO\ SRLQWHG DW D VWDU ƅOOHG
region of sky. The app is user-friendly and makes it
simple to select targets.

It’s also possible to manually enter coordinates of,
say, a comet or a supernova that’s recently appeared,
although Unistellar periodically adds such targets
to the app. It also has a citizen science dimension,
asking users to observe asteroid occultations,
exoplanet transits and ‘planetary defence’ tasks
(potentially hazardous asteroids). Observational data
can then be uploaded for analysis by scientists at
Unistellar and the SETI Institute.

The eQuinox is an easy-to-use telescope that
works very well in brightly lit urban areas, with the
ERQXV RI KDYLQJ D VFLHQWLƅF DVSHFW ,WŝV D QHZ W\SH
of telescope inspired by professional, ground-based
telescopes – after all, the science of astronomy is
GRLQJ MXVW ƅQH ZLWKRXW H\HSLHFHV

88 BBC Sky at Night Magazine September 2021



Our experts review the latest kit

FIRST LIGHT

Founder Optics

FOT106 triplet refractor

A telescope that delivers an impressive optical performance for observing or imaging

WORDS: TIM JARDINE

VITAL STATS W ith an established reputation Air-spaced acuity
for quality and high-end
• Price £2,159 performance, Japanese The FOT106 objective lens uses three distinct
package with optical systems are held in elements to achieve apochromatic colour correction,
field-flattener high regard, so we received and two of these are made of extra-low dispersion
(or £1,999 OTA the new Japanese-designed (ED) glass, namely FPL-53 and FPL-51. Fully multi-
only; optional Founder Optics FOT106 triplet refractor for review coated to minimise reflections, these lenses are
field-flattener with keen anticipation. separated by air-filled spaces, an approach to lens
at £179) design also adopted by Takahashi TOA telescopes.
The telescope is supplied in an aluminium case
• Optics with useful accessories and our package included a Of course, performance with an eyepiece or a
Air-spaced PDWFKLQJ ƅHOG ƆDWWHQHU )URP WKH RXWVHW ZH ZHUH camera is what really counts. We viewed the bright
apo triplet impressed with the overall look of the telescope; the edge of a near-full Moon at high power to check for
UHIUDFWRU LV ƅQLVKHG WR D YHU\ KLJK VWDQGDUG ZLWK D any unwanted colour-fringing or haloes along the
• Aperture distinctive gloss black tube and vibrant metallic focused edge, an effect that can translate into
106mm JUHHQ DQRGLVLQJ IRU WKH ƅWWLQJV :H DOVR QRWHG WKDW coloured rings around bright stars in astro imaging,
it weighs a reassuringly chunky 6.7kg thanks to its but the view was sharp and free of chromatic
• Focal length solid construction. aberrations. Although suitable photographic targets
636mm from our observatory were limited by the time of
:KHQ LW FRPHV WR RSWLFV WKH )27 ERDVWV DQ I year, we were able to grab a series of images of the
• Focuser Rack 106mm objective lens with a focal length of 636mm, Dumbbell, Veil and Eagle Nebulae. With their tight,
and pinion making it ideal for observing or photographing larger natural-coloured stars these images confirmed the
FOXVWHUV JDOD[LHV DQG QHEXODH :LWK WKH GHZ VKLHOG impressive optical abilities of the FOT106.
• Extras and focuser retracted the tube assembly is a
ALL PICTURES: @THESHED_PHOTOSTUDIO Field-flattener, FRPSDFW PP LQ OHQJWK :LWK WKH GHZ VKLHOG IXOO\
carry handle, H[WHQGHG DQG D ƅHOG ƆDWWHQHU SOXV FDPHUD Ś RU VWDU
lens cloth, GLDJRQDO DQG H\HSLHFH Ś DWWDFKHG WKH WHOHVFRSHŝV
Inspection working length is around 800mm.
Report and
owner’s Considering that there are three pieces of glass at
manual the working end, it was nice to see that the balance
point of the tube was reasonably central. This made
• Weight 6.7kg it comfortable to use for observing, and easier on a
(with tube mount for astrophotography.
rings; 5.5kg
without) Test conditions

• Supplier Despite having the Inspection Report card, we were
Widescreen NHHQ WR GR RXU RZQ VWDU WHVW WR FRQƅUP WKH ƅQGLQJV
Centre It was a warm evening, so we allowed plenty of time
for the telescope to cool. Our Ronchi eyepiece
• Tel 01353 returned an almost identical pattern to that on
776199 the report and demonstrated that there was no
astigmatism or other glaring optical aberrations.
• www.
widescreen- :LWK D PP H\HSLHFH ZRUNLQJ DW [
centre.co.uk PDJQLƅFDWLRQ DQG WKHQ FRPELQHG ZLWK D [ %DUORZ

OHQV WR GHOLYHU [ SRZHU ZH REVHUYHG D FHQWUDOO\
positioned star and gently rolled through either side
of focus, noting the star pattern. If anything, what we
REVHUYHG ZDV HYHQ EHWWHU WKDQ WKH DUWLƅFLDO VWDU WHVW
image given on the Inspection Report, with a ring
pattern demonstrating a high level of correction. This >

90 BBC Sky at Night Magazine September 2021

Tube rings and SCALE
carry handle
Owner’s manual and Inspection
Stylish green tube rings and Report card
a Vixen-style mounting bar
provide a solid link between The underside of the focuser is stamped with a serial number, which
the FOT106 and the mount. matches that on the laminated Inspection Report and provides an
A custom carry handle bolts LQGLYLGXDO YHULƅFDWLRQ RI WKH VFRSHŝV RSWLFDO DQG PHFKDQLFDO TXDOLW\ 7KH
securely onto the top of the SULQWHG RZQHUŝV PDQXDO LV D QLFH WRXFK WKDW JLYHV WLSV RQ WHOHVFRSH
rings and incorporates a assembly, accessories and the correct use of the equipment.
mounting rail for a red dot
ƅQGHU $OO WKH QHFHVVDU\ EROWV
are included in the package.

Field-flattener Focuser

7KH LQFOXVLRQ RI D PDWFKLQJ ƅHOG The 2.7-inch focuser is a strong hybrid rack
ƆDWWHQHU PDNHV WKLV WHOHVFRSH DQ and pinion design, offering smooth, precise
almost out-of-the-box solution for
astrophotography. It has a 2-inch focusing with 1:11 reduction. Capable of
QRVHSLHFH WKDW LV KHOG ƅUPO\ E\ WKH holding 8kg, the drawtube is graduated and
twist and lock collar on the focuser,
and the M42– and M48–threaded the whole assembly is easily rotated for
adaptors for cameras offer a comfortable viewing positions. In addition,
straightforward attachment to
a CMOS camera or DSLR T-ring. the rear section rotates independently,
allowing you to easily frame targets or
quickly alter the positions of eyepieces.

September 2021 BBC Sky at Night Magazine 91

FIRST LIGHT

KIT TO ADD > JDYH XV FRQƅGHQFH WKDW WKH

1. %DDGHU SHUIRUPDQFH RI WKH WHOHVFRSH

6N\6XUIHU 9 VKRXOG EH H[FHOOHQW DQG D

UHG GRW ƅQGHU YLVLW WR (SVLORQ ¡ /\UDH WKH

2. :LOOLDP 2SWLFV IDPRXV 'RXEOH 'RXEOH VWDU Carry case
'XUD %ULJKW UHYHDOHG D FOHDQ DQG GLVWLQFW
LQFK 'LHOHFWULF VSOLW EHWZHHQ LWV IRXU FORVHO\ The foam-padded, locking carry case protects the telescope in transit
or storage, holding the complete package conveniently together,
&DUERQ )LEUH SDLUHG PHPEHUV
LQFOXGLQJ WKH ƅHOG ƆDWWHQHU DQG ULQJV $W MXVW FP [ FP [ FP
'LDJRQDO :LWK WKH )27 VHW XS IRU the case is very manageable and enhances the portability of
WKH )27 ZKLOH WUDYHOOLQJ SHUKDSV WR GDUNHU VNLHV
3. 7HOH9XH PP REVHUYLQJ ZH HPEDUNHG RQ D
3O¶VVO H\HSLHFH WRXU RI VRPH RI RXU IDYRXULWH > A single shot of

LQFK GHHS VN\ REMHFWV 2XU PP the Moon, taken
with the FOT106
p H\HSLHFH HQDEOHG XV WR refractor and a
standard Canon
HQMR\ VRPH YHU\ FRPIRUWDEOH YLHZLQJ DW [ EOS 6D DSLR (full
frame) – with 1/640”
PDJQLƅFDWLRQ DQG ZLWK D UDQJH RI JOREXODU FOXVWHUV exposure at ISO 100

JUDFLQJ WKH VNLHV ZH ZHUH DEOH WR HQMR\ FULVS þ A cropped image

FRQWUDVW ULFK YLHZV RI WKHP LQ FRQWH[W EHIRUH of the Eagle Nebula,
M16, taken with the
VZLWFKLQJ WR D PP H\HSLHFH IRU D FORVHU YLHZ $Q same setup – with
1 hour 18 minutes
LPPHUVLYH YLHZLQJ H[SHULHQFH ZLWK RXU PP p of 60” exposures
at ISO 1000
H\HSLHFH ZDV HVSHFLDOO\ PHPRUDEOH ZLWK WKH ORZ

PDJQLƅFDWLRQ RI [ SURYLGLQJ VXSHUE ZLGH YLHZV :H

DGGHG D YLVXDO 2,,, 2[\JHQ ƅOWHU WR HQKDQFH WKH

SODQHWDU\ QHEXODH 0 DQG 0 ZKLFK ZHUH QRWDEO\

EULJKW REMHFWV DPRQJ D VHD RI VWDUV

@THESHED_PHOTOSTUDIO, TIM JARDINE X 3 Field-flattener option VERDICT +++++ Þ The Great
+++++
$OWKRXJK ZH FRXOG KDYH HQMR\HG WKH UHZDUGV RI Build and design +++++ Cluster in Hercules,
YLVXDOO\ REVHUYLQJ WKH VNLHV IRU PXFK ORQJHU ZLWK WKH Ease of use +++++ M13 (cropped),
)RXQGHU 2SWLFV )27 ZH ZHUH FRQVFLRXV RI WKH Features +++++ taken with the
VXPPHU QLJKWV GXULQJ RXU UHYLHZ SHULRG QRW EHLQJ Imaging quality ++++ same setup – with
SDUWLFXODUO\ GDUN RU ORQJ VR ZH UHPRYHG WKH YLVXDO Optics 1 hour 17 minutes
DVWURQRP\ DFFHVVRULHV DQG DWWDFKHG WKH ƅHOG OVERALL of 90” exposures
ƆDWWHQHU WR RXU '6/5 FDPHUD 7 5LQJ YLD WKH 0 at ISO 800
DGDSWRU RSWLRQ WKDW LV SURYLGHG

7KH RZQHUŝV PDQXDO VWDWHV WKDW WKH XVHIXO LPDJH
FLUFOH RU FLUFOH RI LOOXPLQDWLRQ ZLWK WKH ƅHOG ƆDWWHQHU
LQ SODFH LV PP VRPHWKLQJ RXU IXOO IUDPH '6/5
ZRXOG WHVW WR WKH OLPLW :H SKRWRJUDSKHG VWDU ULFK
DUHDV DQG ORRNHG FDUHIXOO\ DW WKH UHVXOWV

,QGHHG ZH IRXQG WKDW WKH FHQWUDOO\ SODFHG VWDUV
ZHUH URXQG DQG SLQ VKDUS DV H[SHFWHG ZKLOH WKH VWDU
VKDSHV WRZDUGV WKH FRUQHUV DQG HGJHV RI WKH LPDJH
VWDUWHG WR VKRZ WKH HIIHFWV RI FRPD WKH VWDUV
EHFRPLQJ D OLWWOH VWUHWFKHG DQG ODUJHU $V DQ HVWLPDWH
ZH ZRXOG VD\ WKDW D FURS RI DQ DUHD DERXW Ś SHU
FHQW RI WKH IXOO IUDPH LPDJH VL]H ZLOO OHDYH DFFHSWDEOH
VWDU VKDSHV ZKLFK VKRXOG EH MXVW DERXW ULJKW IRU
'6/5 DQG &026 FDPHUDV ZLWK $36 & VL]H VHQVRUV
RU VPDOOHU

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)27 PD\ EH WKH QH[W WHOHVFRSH WR FODLP LWV SODFH
DPRQJ WKH UDQNV RI HVWHHPHG -DSDQHVH GHVLJQHG
RSWLFDO HTXLSPHQW

92 BBC Sky at Night Magazine September 2021



New astronomy and space titles reviewed

BOOKS

tour of some of these solved and not-so- Interview with
the author
solved topics. He propels us across the Paul Davies

development of post-Einsteinian What cosmological
questions remain
cosmology, often including his own unsolved?

modest contributions, as well as covering Did the Universe
originate a finite
ideas about time and space, black holes, time ago, or has
something always existed? Or, to
LQƆDWLRQ GDUN HQHUJ\ DQG GDUN PDWWHU express it more bluntly, did time
itself begin with the Big Bang?
Davies’s lucid style has allowed the book
What is the Cosmic Microwave
some freedom of movement and Background (CMB)?

anecdotal diversion, giving the impression It is the fading afterglow of the Big
Bang. When the Universe erupted
that a story is being told; although each into existence 13.8 billion years ago,
it was immensely hot. That heat
chapter is a short vignette that can be radiation suffused all space, but
as the Universe expanded, the
read in complete isolation. temperature declined, so that today
it forms a pervasive background of
7KH ƅQDO TXDUWHU RU VR RI WKH ERRN microwaves, like a vast cosmic oven.

moves into slightly more speculative or What might the ‘super-void’ be?

philosophical areas of modern science. Cosmologists are stumped. It looks
like something banged into our
Davies discusses multiverses, the Universe, which is a rather outlandish
theory, but who knows? More
anthropic principle, life in the Universe, the conservatively, the simple picture we
have of inflation – when the Universe
eventual fate of the cosmos, the thorny jumped in size by a huge factor in the
first split second – might be an
What’s Eating topic of ‘reductionism’, and the meaning over-simplification, and some sort
the Universe? of science itself. These areas are covered of quantum vacuum disturbance has
with equal reserve and restraint, and left a blemish on an otherwise almost
FRPSOHPHQW WKH PRUH GHƅQLWLYH FRQFHSWV exactly smooth cosmic organisation.
previously introduced.
Where can cosmologists look to solve
Paul Davies As a populariser of often this mystery?

Allen Lane arcane science, Davies is There are many theoretical models of
the early Universe, some involving
£16.99 z HB second to none. Having either ‘other universes’ or a cosmic
honed his skills in well phase that preceded the Big Bang.
The challenge they face is to match
It is little more than over two-dozen the known cosmic features but, in
addition, to give explanations of the
a century since books, there is little anomalies. So far there is no stand-
out competitor. It’s still a mystery.
the nature of to fault in his style
Paul Davies is a Regents Professor
gravitation, the or his ability to
of Physics and Director of the Beyond
abstractness of reduce concepts Center for Fundamental Concepts in
Science at Arizona State University
the quantum world to their minimum.

and the true extent Keeping it

of the Universe were entertaining, the text

ƅUVW SHUFHLYHG %XW LQ is informative and

that short time, the unpatronising. There

progress in our are much better books

cosmological understanding Concepts are skilfully explaining our current views
has been staggering. We discussed, including on dark matter, dark energy,
have deciphered the earliest multiverses (above) and the LQƆDWLRQ PXOWLYHUVHV WLPH
moments and subsequent meaning of science itself travel, and so on. However,
history of the Universe to these are often more

such an extent that our insights about detailed and taxing than the armchair

FOTOJOG/ISTOCK/GETTY IMAGES the origins of our own planet pale in enthusiast requires. What’s Eating the

comparison. Although this insight has Universe? ƅOOV D QLFKH QLFHO\ Ś LW FDQ EH
been astounding, there are of course
read in a single afternoon. ★★★★★

many mysteries still occupying modern

astrophysics and cosmology. Dr Alastair Gunn is a radio

In this rather short book, cosmologist astronomer at Jodrell Bank

Paul Davies takes us on a whistle-stop Observatory in Cheshire

94 BBC Sky at Night Magazine September 2021

The Smallest Lights Asteroids SPACE
in the Universe: a memoir ROCK
Martin Elvis SCIENCE
Yale University Press
Sara Seager On the other, there’s a neglectful £20 z HB
4th Estate childhood, a slow-burn love affair, and the
£9.99 z PB dying of Seager’s husband from cancer, Why should
with its subsequent fallout. we explore
“Sometimes you the asteroids?
need darkness At points the book is romantic, and For the love of
to see,” writes filled with awe about space in a way knowledge?
astrophysicist Sara that anyone who loves the stars will Asteroids can
Seager, referring understand. “There are places where teach us about
to the ability of science and magic meet, windows to the formation
astronomers to worlds greater than my own,” writes and evolution of
peer into space, Seager. A professor of physics and our Solar System,
but also to the planetary science at MIT, she has the origins of
losses that life can contributed to the foundations of Earth’s oceans,
bring. “Sometimes exoplanet research and won the organics and even life, so there’s plenty to
you need light.” MacArthur Foundation’s “genius” grant. learn! What about fear? An asteroid
It is this search for the ‘smallest lights LPSDFW ZLSHG RXW WKH GLQRVDXUV Ś LW PLJKW
in the Universe’ that Seager’s book The book’s strength lies in its therefore be wise to keep tabs on them
beautifully chronicles, as both personal intersection with human life: grief, sadness and work out the best way to avoid such
memoir and the story of her quest to and hope. Seager believes there is life a fate ourselves. Or perhaps greed?
explore the Universe. On one side, we get elsewhere in the Universe, but she also Some asteroids contain water, a valuable
a view of what it’s like at the forefront of asks what that search says about us, commodity in space, while others contain
research: chasing exoplanets, studying reminding us that we are “capable of rare or useful metals we could mine to
the biosignatures of possible alien life, generate a handsome profit.
chairing projects for NASA. wonder and wonderful things”. ★★★★★ In the book Asteroids, Martin Elvis
argues that all three of these factors
Shaoni Bhattacharya is a science WRJHWKHU Ś ORYH IHDU DQG JUHHG Ś PDNH
writer and journalist a compelling case for our continued
exploration of these Solar System bodies.
The Greatest Adventure While early chapters consider the whys,
later ones focus on the hows, describing
Colin Burgess scientific studies of asteroids, our efforts
Reaktion Books to survey, track and, if necessary, tackle
£25 z HB them, and the idea of asteroid
SURVSHFWLQJ %\ LQFOXGLQJ DQ LQIRUPDWLYH
Those fascinated Those well versed in human spaceflight overview of our technological capabilities,
with space will find it an enjoyable read, uncovering referring to relevant budgets and costs
exploration and new details that the author has packed throughout, and highlighting the
the many human into the book. Equally, if you are new to inadequacies of current space law,
endeavours to this topic, the book provides a wonderful Elvis makes clear that there are
leave Earth’s overview of space exploration. technological, financial and political
atmosphere never barriers to overcome in the pursuit of
tire of hearing the One notable absence is a lack of these space rocks. Yet despite this, he
stories and events character insights into the people behind remains optimistic and maintains that all
of these missions these space-faring pursuits. At points, this three motives together provide the
told over again, can make it difficult to paint the more necessary incentive.
discovering new, human story that has really driven the Asteroids is a fascinating and, at times,
details that enrich the history further. achievements of the past 60 years. surprising read, packed with useful
The Greatest Adventure covers the information and benefitting from Elvis’s
entire history of human space exploration However, to include such accounts personal accounts throughout. Written in
from the early events that ignited the would probably have meant sacrificing an engaging and entertaining style,
Space Race between the Soviets and US, such comprehensive coverage of events, readers will find it hard to put down.
all the way through to the International and there are plenty of biographies
Space Station, the Soyuz rockets and and other literature referenced to jump ★★★★★
Space Shuttles, to the present, with the off into.
prospect of space tourism and private Dr Penny Wozniakiewicz is a lecturer
companies playing greater roles. It The Greatest Adventure provides an in space science at the University
concludes with a brief reflection on what excellent springboard from which to do so. of Kent
the future holds.
It’s an all-round good read. ★★★★★

Nisha Beerjeraz-Hoyle is a space
and astronomy writer

September 2021 BBC Sky at Night Magazine 95

Ezzy Pearson rounds up the latest astronomical accessories

GEAR

1 1 Celestron Ultima Edge flat
field 1.25-inch eyepieces
4
5 Price from £129 • Supplier Harrison Telescope
Tel 01322 403407 • www.harrisontelescopes.co.uk
96 BBC Sky at Night Magazine September 2021
ADVANCED These eyepieces give a sharp,
clear image – from the centre

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PP PP PP PP DQG PP IRFDO OHQJWKV

2 2 Astro Engineering Rigid 8-inch dew
3 shield

6 Price £56.90 • Supplier Telescope House
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Clear the dew away from your optics and protect
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,W ƅWV DURXQG WXEHV ZLWK D GLDPHWHU EHWZHHQ PP
DQG PP DQG LWŝV KHOG LQ SODFH ZLWK Q\ORQ VFUHZV

3 StellarMira 2-inch Field-Flattener
with M42 adaptor

Price £79 • Supplier First Light Optics
Tel 020 3384 5187 • www.ƅUVWOLJKWRSWLFV FRP

Remove the curvature of your scope’s view without
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It’s optimised for DSLRs and scopes with a focal ratio
RI I WR I DQG KDV DQ LQWHJUDWHG 0 DGDSWRU

4 Orion PinPoint Astrophotography
Telescope Focusing Masks

Price from £26.99 • Supplier Orion Telescopes
Tel 0800 041 8146 • https://uk.telescope.com

Ensure your astro images have pinpoint focus with
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D YDULHW\ RI VL]HV DQG KDYH WKUHH DGMXVWDEOH EROWV WR
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5 Solar System glow lamps

Price £110.90 • Supplier The Decor House
https://thedecorhouse.co.uk

Warm your home with the glow of this set of eight
lamps, representing the Solar System’V SODQHWV (DFK
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RI LOOXPLQDWLRQ DQG KDV D ZRRGHQ VXSSRUW FUDGOH

6 Rab Mens Force Long Sleeve Tee

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Layers are key for staying warm through a long
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Our HI-LUX coating can be applied to almost any

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