1. FULL GUIDE TO EUROPEAN ASTROFEST 2016
POLESTARPUBLICATIONS
£4.75 February 2016
AWESOME
AURORAEexploreTHEGREATESTLIGHT
SHOWSinthesolarsystem
ASTRONOMYNOWFEBRUARY2016•AWESOMEAURORAE•CERES’SALTYSECRETS•THENAMEGAME•VOL30NO2
saltyceres
surrenders
its secrets
howDOASTRO
OBJECTS GET
THEIR NAMES?
beginners
guide to MARS
howdarkis
your sky?
001_Cover_Feb16.indd 1 11/01/2016 16:50
2. Sadr image courtesy Geoffrey Lenox-Smith
Star Adventurer Available Now!
NEW Sky-Watcher
‘Star Adventurer’
Multi-purpose
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value from £219.00
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Introducing the NEW 5-element
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STAR-71mm f/4.9 Imaging OTA with FPL 53 glass.
5 elements, 3 groups, 45mm imaging circle.
2.5” focuser - M48 thread & Canon EOS adapter.
Includes mounting rings and Vixen style dovetail.
Weighs 2.4 kg with tube rings & dovetail.
Optional dedicated 1.25” dielectric diagonal.
An optional soft carry case is available separately.
See the Star-71 at Widescreen’s events including
Astrofest 2015 (Feb 6-7) and the monthly BSIA
meetings. William Optics Star-71 from £949.00
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The Questar has been in
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since 1950 and is
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Standard model 3.5” starts from £3,999.00
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ETX80 • 90
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Flight legal in certain sizes, you can now carry with you
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The long-awaited breakthrough in power cell
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Tracer Lithium Polymer 8Ah - £119.99; 10Ah - £149.99;
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We Know William Optics
The William Optics ZS71
Here at Widescreen we get to understand all
of our products. We’re hands-on experienced
amateur astronomers and are passionate
about getting you the right product. When
our suppliers update a product or bring out a
new one - we make sure we understand why.
That’s why we like William Optics.
A constantly evolving product line means
you know that they are monitoring cutomer
feedback & always striving to supply a better
product - just like us. The new ZS71 is a case
in point. With a reliable, full-size 2” focuser
and a dedicated flattener, it will go anywhere
with you. Even on vacation this winter.
And at way under £500, it’s exceptional value.
We think through everthing we sell to our customers. Not just the class-leading
scopes from William Optics. If you buy from us, it’s a safe purchase, backed up
by our own experience. We live in a mobile Universe. Set your sights high.
And see for yourself this winter.
The Zenithstar 71
Special Offer on ZS71 +
Flattener 6:- £439.00
22Ah
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47 Dorset Street • London • W1U 7ND • Baker Street
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Come to the Widescreen booth at
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products in action - SkyFi USB,
SkyWire, Starry Night, and the multi-
award winning ‘SkySafari 5’ App &
desktop software.
6” £1280 CALL
8” £1925 CALL
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The Widescreen Centre
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Hot New Products & great deals in store now!
This August - join us on Saturday
10th for a great family day out - the
SouthWest Astronomy Fair at the
Norman Lockyer Observatory at
Sidmouth in Devon - EX10 0NY.
See www.normanlockyer.com for
more details. We’ll have our usual
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Call us (020) 7935 2580 and ask if
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Widescreen supports The Baker Street Irregular Astronomers. Chance to check out our products after dark. *See www.bakerstreetastro.org.uk for more details
Canon 60Da body £1174.99
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Join The Widescreen Centre and the BSIA in Regent’s Park this summer. It’s fun, it’s free and it’s for everyone.
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Widescreen: Lunt Solar
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Stay cool in the heat. Every month
we join London’s coolest Astronomi-
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in real time to explore the skies.
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Following
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New Tele Vue 85 w/dual-speed focuser £2049
Lunt LS152THa -
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But much, much more....
• top notch review from Sky
At Night’s Pete Lawrence
LS35, LS60, LS80, LS100 and LS152 available
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Telescopes. Mounts. Eyepieces. Barlows & Powermates.
Accessories & Imaging
See the world’s best from London’s Tele Vue Demostrating
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August 10th
September sees the arrival of the
hotly-anticipated Sky-Watcher EQ8.
We will have
this mount
in stock,
on display
and in action
at the
Equinox
Star Party,
Kelling Heath.
More next
month on the
new Flagship
EQ8 mount...
See www.starparty.org.uk - later
this year on the weekend of 4th -
6th October 2013. NR25 7HW
Next meetings
August 14th
September 11th
New EQ8
from
£2500
Next meetings
August 14th
September 11th*
*until August 26th or while stocks last
18:37
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Eclipse photo: Orion StarBlast 62 Simon Bennett
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Next on the calendar!
It’s
In London
February 5-6th 2016
The Universe returns to London
this month! Join us at Astrofest
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www.europeanastrofest.com
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Dowload our App for extra special
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Make the leap to Tele Vue in 2016.
I frequently get asked “Which Tele
Vue eyepice should I buy first?”
My answer - it doesn’t matter!
As soon as you’ve experienced
one, you will inevitably be drawn
back for more. See the universe as
it’s meant to be seen today.
Tele Vue Optics, from Chester,
New York. Nothing else comes
47 Dorset Street • London • W1U 7ND • Baker Street
www.widescreen-centre.co.uk • 020 7935 2580 • simon@widescreen-centre.co.uk
- at The Widescreen Centre
New Tele Vue DeLite
at Astrofest!
Your one-stop London
47 D
Th
47 Dorset St
www.widescreen-centr
17Ah
22Ah
Vacations will never be the same again. W
new Tracer Lithium polymer power packs
travel with enough power to see you throu
No more fumbling for spare AA batteries a
Flight legal in certain sizes, you can now
what you need - and recharge it on the go
The long-awaited breakthrough in power
technology is here for your telescope - an
reason to run out of camera or mobile po
Tracer Lithium Polymer 8Ah - £119.99; 10
14Ah - £179.99; 22Ah - £229.99.
All in stock now at Widescreen.
We Know William Optics
The William Optics ZS71
Here at Widescreen we get to understand all
of our products. We’re hands-on experienced
amateur astronomers and are passionate
about getting you the right product. When
our suppliers update a product or bring out a
new one - we make sure we understand why.
That’s why we like William Optics.
A constantly evolving product line means
you know that they are monitoring cutomer
feedback & always striving to supply a better
product - just like us. The new ZS71 is a case
in point. With a reliable, full-size 2” focuser
and a dedicated flattener, it will go anywhere
with you. Even on vacation this winter.
And at way under £500, it’s exceptional value.
We think through everthing we sell to our custom
scopes from William Optics. If you buy from us,
by our own experience. We live in a mobile Univ
And see for yourself this winter.
The Zenithstar 71
02_widescreenad_Aug13.indd 2
It’s back! 5th & 6th February in London.
Widescreen will be there, booths 1-6
+ 7-9. Visit us at the show- or see
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Widescreen Centre
Personalised
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Valid 1 year,
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2016
Eclipse photo: Orion StarBlast 62 Simon BennettEclipse photo: Orion StarBlast 62 Simon BennettM45 image by Gordon Haynes with Tele Vue NP127FLI visit www.imagingtheheavens.co.uk
002_widescreenad_feb16.indd 3 11/01/2016 15:12
5. • Control your telescope right from your device using SkyPortal
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• Works with Celestrons’ brand new planetarium App, SkyPortal.
• SkyPortal App turns your smartphone or tablet into your own
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Celestron®, SkyPortalTM
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David Hinds Ltd is an authorised distributor and reseller of Celestron products. iPhone and App Store are registered trademarks of Apple Inc. Google Play is a registered trademark of Google Inc.
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Engineered from the ground up with astroimaging in
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12026 - Advanced VX 8 SCT
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12046 - Advanced VX 9.25 SCT
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CelestronisdistributedintheUK&IrelandbyDavidHindsLimited.Tradeenquirieswelcomed.
TECHNOLOGICALLYSUPERIOR
• Set your telescope outside, press ‘Align’ on the StarSense hand
control, and sit back. No further user involvement needed!
• StarSense uses an on-board digital camera to scan the sky.
• In about 3 minutes StarSense will gather enough information
to triangulate its position and align itself.
• No need to identify or manually locate
alignmentstarsinthesky,StarSensewill
automatically align your telescope.
• Sky Tour mode will slew to all the
best stars, planets, galaxies and
more based on your exact time
and location.
• Provides advanced
mount modelling.
Celestron
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Control your Celestron computerised telescope using
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Upgrade your Celestron computerised telescope
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JN100715_CELESTRON_FULLPAGE-ANOW-AW.indd 1 23/7/15 10:21:43
132_OBCad_sep15.indd 132 07/08/2015 17:53
6. CONTENTS
6
Volume 30 • Number 2 • February 2016 • ISSN 0951-9726 • Printed in the UK
Navigate to your favourite Astronomy Now articles in this issue.
REGULARS60 THE NIGHT SKY
37 THE NAME GAME
The naming of astronomical objects is no simple
matter, on occasion leading to acrimony and
controversy, but which now also has increasing
input from the public, writes Keith Cooper.
9 News update
26 Key moments in astronomy
60 The night sky
88 The Universe for beginners
94 Imaging for beginners
99 Ask Alan
100 Astro-imaging masterclass
111 Book reviews
112 Astroloot
116 Grassroots astronomy
118 Astrolistings
120 Classifieds
123 Picture gallery
62 Top targets for beginners
66 Moonwatch
68 Sky scene
70 Southern sky
72 Object of the month
77 Planets at their best in 2016
78 Deep Sky challenge
80 Constellation of the Month
30 TRIPPING THE LIGHT FANTASTIC
We are all held in awe by the beauty of the aurorae that dance in the
skies of the Earth’s northern and southern hemispheres, but these
etherial curtains of light aren’t unique to our planet. Isadora Fontaine
takes a trip around the Solar System’s auroral displays.
14 Andromedae
Veritate (from the Latin ‘veritas’, meaning truth)
Spe (meaning ‘hope’ in Latin)
HD 104985
Tonatiuh (Aztec god of the Sun)
Meztli (Aztec goddess of the Moon)
51 Pegasi
Helvetios (Latin phrase referring to a MedievalCeltic tribe that lived in Switzerland)
Dimidium (Latin for ‘half’, because
the planet is half the mass of Jupiter)
18 Delphini
Musica (Latin for ‘music’)
Arion (ancient Greek poet)
HD 149026
Ogma (in Celtic myth Ogma is thegod of eloquence and writing)
Smertrios
(Gallic god of war)
xi Aquilae
Libertas (Latin for ‘liberty’)
Fortitudo(Latin for ‘fortitude’)
42 Draconis
Fafnir (a character from Norse mythology whoturned from a dwarf into a dragon)
Orbitar (A play on the word ‘orbiter’)47 Ursae Majoris
Chalawan (A mythological crocodilefrom a Thai folk tale)
Taphaeo Thong
Tapheo Kae
(These are sistersassociated with the samefolk tale about Chalawan)
Copernicus (named after Nicholas Copernicus)
Harriot (named after Thomas Harriot, who
may have been the first to use a telescope for astronomy)
Galileo (named afterastronomer Galileo Galilei)
Brahe (named afterastronomer Tycho Brahe)
55 Cancri
Lippershey (named after Hans Lippershey, theoptician who invented the telescope)
Janssen (named after Jacharias Janssen, who invented the microscope and
may have had involvement in the telescope’s invention)
Cervantes (the Spanish author of the Don Quixote stories)
Quijote (lead character inthe Don Quixote stories)
Dulcinea (Don Quixote’s
love interest)
mu Arae
Rocinante (Don Quixote’s steed)Sancho (Don Quixote’s squire)
Lich (a fictional undead creature that has magical
powers to control other undead creatures)
Draugr (undead creatures
of Norse mythology)
Poltergeist (A malevolent
ghost or spirit)
PSR 1257+12 (pulsar)
Phobetor (the Greek god of nightmares)
epsilon Tauri (Ain)
Amateru(a Japanese appellation forshrines to the Shinto goddessof the Sun, Amaterasu)
iota Draconis (Edasich)
Hypatia(an ancient Greek scientistand philosopher)
gamma Cephei (Errai)
Tadmor (a Semitic name and modernArabic name for the city of Palmyra,which is a World Heritage Site)
Geminorum (Pollux)
Thestias (the patronym of Leda andAlthaea, daughters of Thestius and Leda
mother of Pollux and his twin Castor)
alpha Pisces Austrini (Fomalhaut)
Dagon(a semitic deity represented ashalf-man, half-fish – theconstellation Pisces Austrinusis known as the Southern Fish)
epsilon Eridani
Ran (the Norse goddess of the sea)
AEgir (Ran’s husband andgod of the ocean. The use ofthe capital E is to differentiateit from one of Saturn’s moons
called Aegir)
Titawin (a World Heritage Site in Morocco and a point
Saffar (named after a scientist
upsilon Andromedae
of contact between Spanish and Arab
civilisations, and between Europa andAfrica, after the 8th century)
and mathematician in 11thcentury Andalusia)
Samh (named after an astronomerMajriti (named after a mathematician and scientist
who taught in 10th and 11th century Andalusia)
and mathematician in 11th century Andalusia)
HD 81688
Intercrus (means ‘between the legs’ in Latin,
Arkas
referring to the star’s position between
the legs of the Great Bear, Ursa Major)
(the son of Callisto, whowas also known as UrsaMajor, in Greek mythology)
004_editorialcontents_Feb16.indd 6 11/01/2016 16:52
7. February 2016 | Astronomy Now | 7
CONTENTS
ON THE
COVER:
Thismonthwe
takeatourofthe
SolarSystem’s
auroraldisplaysand
discoverhownewly-
discoveredobjects
gettheirnames.
84 HOW DARK IS YOUR SKY?
The introduction of dark-sky meters has made measuring night sky darkness
easy. Or has it? John Rowlands takes a closer look at how to get it right.
105 BEYOND THE RAINBOW: GAMMA RAYS
Last month, we introduced you to the Electromagnetic spectrum and its uses in modern
astronomy. In this issue, Jenny WWinder begins our detailed journey through the spectrum.
We start at the most energetic end of the spectrum: Gamma Rays, and we explore what they
reveal about the workings of the Cosmos.
s the
ing)
s
undead creature that has magicalo control other undead creatures)
Draugr (undead creatures
of Norse mythology)
Poltergeist (A malevolent
ghost or spirit)
Greek god of nightmares)
Morocco and a point
after a scientist
en Spanish and Arabbetween Europa andter the 8th century)
matician in 11th
tury Andalusia)
n astronomer
nd scientist
Andalusia)
y Andalusia)
54 CERES’SALTY SOLUTION
As Dawn spirals ever closer to enigmatic Ceres,
scientists celebrate the solving of a major
mystery on the dwarf planet.
004_editorialcontents_Feb16.indd 7 11/01/2016 16:52
8. The Infinity
For stunning views
in seconds.
The Infinity breaks the barrier between visual observing and
astrophotography. It combines the experience of observing at the eyepiece
with a level of depth and detail that would traditionally be the result of several hours
processing. This takes a camera that's sensitive enough to capture faint details on distant objects, and fast
enough to do it in real time. It then takes our powerful, intuitive software to bring stunning views of the night sky
to a screen in just seconds.
This recreates the feel of observing in
the field through a very large
telescope, only using much more
modest equipment. You stay
connected to the night sky, watching
satellites drift across your field of
view, while viewing objects previously
out of reach to all but the most
powerful eyepieces and the largest
apertures.
See the faint connecting filaments in
MSl while planning your next move
in your star atlas. See bok globules in
the Pelican Nebula as you dodge the
clouds. Dive deep into the NGCs of
Andromeda - and do it all in colour.
Although our eyes aren't sensitive
enough to see the universe in colour,
the Infinity is. Faint grey fuzzies
become detailed areas of colourful
nebulosity, allowing you to go beyond
the limits of our vision.
But our own vision isn't our only
limitation. Light pollution is a growing
problem for all of us, with backyard
observing becoming increasingly
difficult in many places. The Infinity
helps you cut through the pollution to
bring observing back to our urban
areas.
It also helps you share the
breath-taking things we see and
discover as astronomers. By cutting
the queue to the eyepiece, the
Infinity allows everyone to explore
the night sky not just together, but at
the same time. You can discuss
details and anomalies as you see
them, and remove the need for
special skills in averted vision.
This makes it the perfect tool for
public outreach, as well as observing
with family and friends. But the
Infinity doesn't just provide you with
incredible live views. It also allows
you to save single images and even
whole sessions to share later. You can
even broadcast your session live
online to a global audience, right
from inside our software.
But surely something this advanced
involves additional specialist
equipment and complex software?
That's the best bit. The Infinity is
Atik Cameras are available from most major astronomy retailers.
For a full list of stockists, visit us online.
designed to work from a focal length
of around 300mm right through to
1500mm. It works with alt/az
fork-mounted telescopes as well as
equatorial mounts. As long as you can
track a star for a few seconds, it will
work with an Infinity, without the
need for complicated guiding systems.
The camera itself uses the latest in
CCD technology to provide incredible
sensitivity at very low noise, and it's
all controlled through our custom built
software. You want to spend your time
exploring the universe, not learning
our program, so we've kept it as
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still giving you the power and control
you need to delve deep into the night
sky.
Want to know more?
Find us at:
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:111ATIK•••• CAMERAS
008f)
008_atikad_jan16.indd 8 07/12/2015 12:47
9. For news updates, visit www.astronomynow.com NEWS UPDATE
T
he mystery of the puzzling blue stragglers appears to have been
solved, thanks to Hubble Space Telescope observations that indicate
they are created when matter transfers from a red giant to a smaller
companion star.
The discovery, made by a team led by Robert Mathieu of the University
of Wisconsin–Madison and including his former student Natalie Gosnell,
who is now at the University of Texas, involved Hubble observations of
the open star cluster NGC 188, which is 5,500 light years away in the
constellation Cepheus.
Blue stragglers are most obvious in star clusters, where all the stars
are approximately the same age. Astronomers have noted that some stars
in clusters appear too hot and blue for their age, as measured against the
age of the cluster. Hence they ‘straggle’ behind the evolution of the other
cluster stars. Is this strange state of affairs caused by the collision and merger
of stars, or by binary star systems transferring matter from one star to the
other? In the latter scenario, a red giant star would lose its diffuse outer
atmosphere to a smaller, close-by star. The smaller star is rejuvenated by the
extra material, while the red giant is whittled down to become a white dwarf.
In 2011 Mathieu and Aaron Geller of Northwestern University in
Illinois used the WIYN telescope on Kitt Peak in Hawaii to determine
that over three-quarters of blue stragglers have companions, but what
kind of companions are they? Analysing subsequent
data from Hubble, Natalie Gosnell found that of 21
blue stragglers in NGC 188, seven had white dwarf
companions. Another seven showed evidence of mass
transfer. Taken together, the results indicate that at
least two-thirds of the blue stragglers in NGC 188 are
created through mass-transfer. This fraction could be
even higher since Hubble is only able to detect white
dwarfs no older than 300 million years.
The observations, published in the 1 December
2015 issue of The Astrophysical Journal, are the first
direct evidence that blue stragglers form by stealing
mass from a neighbouring red giant. However, this does
not completely rule out the possibility that some blue
stragglers may form from collisions between stars.
“It’s definitely possible that collisions dominate blue
straggler formation in dense systems, like the cores of
globular clusters”, Gosnell tells Astronomy Now. “And
we think that several blue stragglers in NGC 188 are
also formed through collisions, but not as many as
those formed through mass transfer.”
Vampiric blue stragglers feed off red giants
NEWSupdate
9
An artist’s impression
of the mass transfer
process as a smaller
companion steals gas
from a neighbouring
red giant to give itself
new life as a blue
straggler. Image:
NASA/ESA/A Feild
(STScI).
009_News_Feb16FIN.indd 9 11/01/2016 19:28
10. For news updates, visit www.astronomynow.com
10 | Astronomy Now | February 2016
NEWS UPDATE
What is a
Damped
Lyman-
Alpha
system?
Lyman-alpha is the name
given to a series of spectral
lines emitted by neutral
hydrogen gas in galaxies.
In a 'Damped Lyman-Alpha'
(DLA) system of the kind
observed by Jeff Cooke and
John O’Meara, intervening
gas clouds with a high
‘column density’ (i.e. the
density of material in an
imaginary cylinder with a
cross-sectional area of a
square centimetre, driven
through a given region
of space between a light-
emitting object and an
observer) of at least 2 × 1020
atoms per cubic centimetre
dampen the Lyman-alpha
emission lines, broadening
them.
The DLAs are thought
to be immense clouds of
primordial gas that wander
t h r o u g h i n t e r g a l a c t i c
space, following the cosmic
web of dark matter. In
the early Universe many
o f t h e m e x p e r i e n c e d
gravitational collapse. As
the clouds collapsed, they
began to spin, while in
their centres temperatures
and pressures grew high
enough to spark intense
star-formation, building
what we see as the central
bulges of spiral galaxies
today. The spiral discs came
later as more gas fell onto
the galaxies.
This picture of galaxy
formation is given only
in broad brush strokes.
With Cooke and O’Meara’s
observations of the DLAs,
coupled with the launch
of the James Webb Space
Telescope in 2018 and the
construction of the next
generation of extremely
l a r g e g r o u n d - b a s e d
telescopes, astronomers
will finally be able to take
greater steps towards
rendering this picture in
sharper focus.
REPORTS FROM THE 227TH
AMERICAN ASTRONOMICAL S
Primordial gas clouds found
silhouetted against distant galaxies
T
he true size of vast but dark clouds of
gas that are large enough to create entire
galaxies has been discovered silhouetted
against the light of distant background objects.
The first galaxies are understood to have
formed from the collapse of giant clouds of
hydrogen gas called ‘Damped Lyman-Alpha’
systems, or DLAs (see box). Most of this
galaxy formation took place in the billion or
so years after the Big Bang, but some of the
DLAs remained. Previously those clouds that
survived the initial round of galaxy formation
were detected by the way they absorb the light
of more distant quasars. However, the light-
producing regions of quasars are the centres of
active galaxies, which are relatively small. There
was no way to determine the sizes of the DLAs
by the amount of quasar light they obscured.
Jeff Cooke of Swinburne University of
Technology in Australia and John O’Meara
of St Michael’s College in Vermont, USA,
realised that if they could detect the clouds
obscuring entire galaxies then it would
provide a better estimate of their size. These
background galaxies would, however, be very
distant and very faint, so, to that end, the
astronomers turned to some of the largest
telescopes in the world – the Keck telescopes
on Mauna Kea in Hawaii and the Very Large
Telescope (VLT) at the European Southern
Observatory in Chile.
“Our new method first identifies galaxies
that are more likely to have intervening DLAs
and then searches for them using long, deep
exposures on the powerful Keck Observatory
ten-metre telescopes in Hawaii and deep data
from the VLT eight-metre telescopes in Chile”,
says Cooke, who presented the results at the
227th American Astronomical Society meeting.
The degree by which the clouds block the
light of a background galaxy gives an indication
of their immense size. Now that some of
these clouds have been identified, Cooke and
O’Meara hope that further investigation will
be able to help piece together how galaxies like
the Milky Way are assembled from the raw
materials in these clouds.
“The technique is timely as the next
generation of giant 30-metre telescopes will be
online in several years and are ideal to exploit
this method to routinely gather large numbers
of clouds for study”, adds O’Meara.
An artist’s impression that depicts how the light
from a distant galaxy is partly absorbed by a
foreground DLA cloud before reaching Earth.
Image: Adrian Malec and Marie Martig.
009_News_Feb16FIN.indd 10 11/01/2016 19:29
11. For news updates, visit www.astronomynow.com
February 2016 | Astronomy Now | 11
NEWS UPDATE
SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016
T
wo massive blasts from the black
hole at the centre of a nearby
galaxy have given the clearest
picture yet of how galaxies expel gas.
Observations with NASA’s Chandra
X-ray Observatory reveal two arcs of hot
material near the centre of NGC 5194,
which is the smaller partner in the Messier
51 system, more famously known as the
Whirlpool. Eric Schlegel, who presented
the findings at the 227th meeting of the
American Astronomical Society, believes
the two arcs to be relics of powerful shock
waves from the black hole that erupted
between three and six million years ago
and that have ‘snow ploughed’ their way
through the surrounding gas.
“It’s the best example of snow-
ploughed material I’ve ever seen”, says
Schlegel. “It’s clearly a way of ejecting gas
from a galaxy.”
NGC 5194 and its larger spiral
partner, NGC 5195, gravitationally
interact with each other. These
interactions have disturbed gas within
NGC 5194, causing it to crash towards
the massive black hole. This material was
then either slingshot around the black
hole, or fell directly onto it, resulting in
a powerful burst of X-rays that rippled
through the surrounding environment like
a shockwave. Surrounding gas is heated to
the point that it can no longer form stars
and the shock wave blows the gas out of
the galaxy. Astronomers call this process
feedback and it is believed to be the major
factor in stopping the growth of massive
galaxies.
“We would expect this process to
happen much more in the early Universe,
where galaxies were crammed in together
and there were more collisions”, he says.
“We need to study the process at other
wavelengths – I’ll be spending the next
few years looking at this.”
Whirlpool’s partner has black hole burp
TheWhirlpool Galaxy and its companion, NGC 5194.
The inset image shows the black hole (centre) and
two expanding arcs beneath it. Image: NASA/CXC/
STScI/University ofTexas/E Schlegel et al.
009_News_Feb16FIN.indd 11 11/01/2016 19:29
12. 12 | Astronomy Now | February 2016
NEWS UPDATE For news updates, visit www.astronomynow.com
Five more stars like the mighty
eta Carinae, which lurks at the
centre of this expanding nebula,
have been found in nearby
galaxies. Image: Jon Morse
(University of Colorado)/NASA.
REPORTS FROM THE 227TH
AMERICAN ASTRONOMICAL
SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016
Five twins of the Milky Way’s most
mysterious star found in nearby galaxies
A
stronomers using the Hubble
and Spitzer space telescopes
have found a quintet of stars
in other galaxies that are just like one
of the most mysterious stars in our
Galaxy: eta Carinae.
Famous for its violent outburst
in 1843 when it became the second
brightest star in the sky and expelled
huge amounts of material into space, eta
Carinae is a stellar monster. It’s actually
two stars, one 90 times more massive
than the Sun, the other 30 solar masses,
and combined they are five million
times more luminous than the Sun. Eta
Carinae is also an incredibly rare type of
star, with no others quite like it known
in our Galaxy, nor anywhere else in the
Universe, until now.
Rubab Khan, at NASA’s Goddard
Space Flight Center, set out to find
some more stars like eta Carinae. He
developed a spectral fingerprint to
search for them in mid-infrared and
ultraviolet light. The dust expelled
by these stars during outbursts blocks
some of the optical and ultraviolet, and
then re-radiates it in infrared light. So
the fingerprint that Khan was searching
for was an excess in infrared as seen
by Spitzer, and a dip in optical and
ultraviolet light as seen by Hubble. Lo
and behold, Khan was able to identify
five stars just like eta Carinae in nearby
galaxies: NGC 6946, Messier 101,
Messier 51 and two in Messier 83. It is
perhaps no coincidence that these four
galaxies are also the most prodigious
producers of core-collapse supernovae
within a 30 million light year radius,
suggesting a connection.
“These stars are very rare and now
we can qualitatively say how rare they
are”, says Khan, who presented his
work at the American Astronomical
Society Meeting. “We are finding one
of these stars for every few hundred
billion stars. Their discovery opens
a new window into studying the
evolution of high-mass stars, how they
live, how they erupt and how they die.”
The findings are published in the 20
December 2015 edition of Astrophysical
Journal Letters.
009_News_Feb16FIN.indd 12 11/01/2016 19:29
14. 14 | Astronomy Now | February 2016
For news updates, visit www.astronomynow.comNEWS UPDATE
A giant, early galaxy cluster
T
he most massive galaxy cluster ever found in the early Universe has been
identified by the cumulative efforts of the Hubble, Chandra and Keck telescopes.
“Galaxy clusters are the most massive collapsed objects in the Universe and,
as such, they are really at the crossroads of astrophysics and cosmology”, says Mark
Brodwin of the University of Missouri in Kansas City, who announced the discovery at
the 227th American Astronomical Society meeting in Florida.
How big galaxy clusters can become depends on how fast they can grow before
dark energy expands the Universe so much that the clusters become starved of new
material falling onto them.As such, the masses of galaxy clusters in the early Universe
are a means of measuring the expansion of the Universe during the first few billion years
after the Big Bang.The light from this new king-sized galaxy cluster, designated IDCS
J1426.5+3508 or known as IDCS 1426 for short, has been travelling for ten billion
years, which puts it at less than four billion years after the Big Bang. Browdin and his
colleagues used different technique’s to measure the cluster’s mass. Hubble and Keck
were able to see the amount of gravitational lensing from the cluster and determine how
much mass it needed.The Chandra X-ray observatory measured the amount of hot gas,
while the Combined Array for Research in Millimetre Astronomy (CARMA) telescope
– which ceased operations in 2015 – was able to measure the effect that the cluster’s
gravity has on the cosmic microwave background radiation and determine the mass
from that.All three methods came up with the same value: 400 trillion solar masses, or a
thousand times the mass of the Milky Way.
Chandra observed that its core of hot gas was not as hot as might be expected from
a newly formed cluster. Instead the gas had cooled somewhat as the cluster dynamically
‘relaxed’ – a feature usually seen in more evolved galaxy clusters.This core of gas is
offset from the centre of the cluster by about 100,000 light years.This is evidence for a
collision about 500 million years earlier with another large cluster.The resulting merger
may have sped up its evolution.
“When it is hit by another cluster, the cool core can slosh around like wine in the
bottom of a wine glass”, says Brodwin.“Eventually it will settle towards the centre, but it
hasn’t settled yet, and that’s how we know it was a recent merger.”
IDCS 1426 will not have stopped evolving ten billion years ago.Today it likely
resembles one of the largest galaxy clusters in the Universe, like a super-cluster of
galaxies such as the Coma Cluster. The findings will be published in a future issue of
The Astrophysical Journal.
AAS meeting
round-up
Distancemattersinbinarybirths
It may be possible to tell how different binary
star systems form by looking at the separation
of their stars, according to astronomers probing
star-forming regions with the Very Large Array
radio telescope in New Mexico, USA. The study, led
by John Tobin of Leiden Observatory, found that
over half of newborn stars are in systems of two or
more and that they could be split into two broad
categories: one where the separation between
the stars is around 75 astronomical units (AU), and
the other where the distance is around 3,000 AU.
Stars with large separations, say the astronomers,
formed through the turbulent fragmentation
of the proto-stellar cloud of gas, whereas closer
partners form in the disc of material that surrounds
the original proto-star.
The black hole missing its stars
A galaxy a billion light years away and thought to
have been involved in a merger with another galaxy
has been found sporting two large black holes, but
strangelyoneofthemismissingitsretinueofstars.
The two black holes are thought to have
originated in the centres of two galaxies that
merged to form the galaxy that we see today,
called SDSS J1126+2944. Supermassive black holes
usually come with a swarm of stars around them,
yet one of the black holes in SDSS J1126+2944
has 500 times less stars than the other. According
to Julie Comerford of the University of Colorado,
Boulder, the black hole may have lost its stars to
gravitational tides during the merger. An alternative
explanation is that the black hole with no stars is of
intermediate mass (around 100,000 solar masses),
which would mean that one of the galaxies that
mergedwasadwarfgalaxy.
“There are very few intermediate mass black
holes known“, says Comerford, who presented
the results at the AAS meeting. “They are hard to
find, but they are an important evolutionary step
towardsbuildingasupermassiveblackhole.”
The quasar that turned itself off
A quasar that was active just twelve years ago has
been seen to suddenly shut down, suggesting that
the black hole at its heart has consumed all the
gas within its vicinity. The Sloan Digital Sky Survey
(SDSS) measured the spectra of the quasar in 2003,
in particular noting the strength of hydrogen-
alpha emission from gas falling towards the black
hole. However, when the SDSS looked again in
2015, the strong hydrogen-alpha emission had
dropped by a factor of 50 and the quasar looked
like a normal galaxy.
“This is the first time we’ve seen a quasar
shut off this dramatically, this quickly“, says Jessie
Runnoe of Penn State University, who led the study
and presented the results at the AAS meeting.
A composite image of IDCS 1426, incorporating visible light observations from Hubble, the
presence of hot gas (blue) seen by Chandra, and infrared light (red) seen by the Spitzer Space
Telescope. Image: NASA/ESA/M Brodwin (University of Missouri).
REPORTS FROM THE 227TH
AMERICAN ASTRONOMICAL
SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016
009_News_Feb16FIN.indd 14 11/01/2016 19:29
16. For news updates, visit www.astronomynow.com
16 | Astronomy Now | February 2016
NEWS UPDATE
Dry planets are wet beneath the clouds
T
he closest known potentially habitable planet beyond our Solar System has
turned up orbiting a red dwarf star just 13.8 light years away.
Astronomers from the University of New South Wales in Australia used the
HARPS (High Accuracy Radial velocity Planet Searcher) on the 3.6-metre telescope
at the European Southern Observatory’s facility in La Silla, Chile, to discover three
Nearest potentially habitable planet found
H
ot jupiters that had appeared dry as a bone
are hiding water vapour under thick clouds,
according to a new study courtesy of the
powerful optics of the Hubble and Spitzer space
telescopes.
In 2014 Hubble observations indicated that three
hot jupiters, which are giant planets extremely close
to their stars, seemed devoid of water vapour in their
atmospheres (see News update, AN, September 2014).
Hubble had observed the planets by comparing the
light of each individual planet and its star combined,
and the light of just the star when the planet was
behind it. The difference between the two is the
light of the planet, and spectroscopic analysis of that
light can indicate which molecules in each planet’s
atmosphere are absorbing light. There didn’t seem to
be much water.
Now we know why. An international team,
including astronomers at the University of Exeter,
surveyed ten hot jupiters – including the dry trio
observed in 2014 – in both optical light and infrared
light, courtesy of Spitzer. Sometimes the planets appear
larger, depending on the wavelength of light they
are observed in: infrared light can penetrate deeper
into the atmosphere and hence a planet can seem
smaller compared to when it is viewed in optical light,
which can be reflected by high-altitude clouds. The
difference between optical and infrared wavelengths
gives some indication as to whether a planet has a cloudy or relatively clear
atmosphere.
“Our results suggest it’s simply clouds hiding the water from prying
eyes”, says Jonathan Fortney from the University of Calfornia, Santa Cruz,
who is a team member and co-author on a paper describing the results in
the 14 December 2015 issue of the journal Nature. “We can therefore rule
out hot, dry, jupiters.”
This will come as a relief to scientists, who had feared that the lack
of water vapour in these planets’ atmospheres meant that something was
amiss in our understanding of how exoplanets form.
An artist’s impression of three worlds orbiting a
red dwarf. Image: NASA/JPL–Caltech.
An artist’s
impression of HD
189733b, a blue
gas giant among
those thought
to have had a
shortage of water.
Image: NASA/
ESA/M Kornmesser.
worlds orbiting the star, named Wolf 1061 (see this month’s
Picture gallery for an image of this star). All three planets have
a low enough mass (1.4, 4.3 and 5.2 times the mass of Earth
respectively) to probably be rocky and one of the planets,
1061c, is tucked snugly within the star’s habitable zone, where
temperatures may be ideal for liquid water to exist on the
planet’s surface.The other two worlds orbit their star just inside
and outside of the habitable zone, and the outermost planet,
d, could also potentially be habitable if it has a thick enough
atmosphere and a strong axial tilt.
The HARPS instrument had been used to search for
planets around Wolf 1061 previously with only hints of their
existence, but improved data processing techniques allowed
the Australian team to tease out the subtle Doppler shift
measurements required to detect the planets. In all, the team
studied more than ten years’ worth of observations of Wolf
1061, which is in the constellation Ophiuchus, close to the
globular cluster M107.
Recent observations of powerful flares on red dwarfs (see
News update, AN, January 2016) suggest they can be deadly
to life on planets orbiting them. Nevertheless, activity on red
dwarfs can vary. Astronomers are seeking to discover whether
these planets also transit their star, which would make them
prime candidates for future study by upcoming missions such
as the European Space Agency’s PLATO spacecraft.
“It is fascinating to look at the vastness of space and think
a star so very close to us – a near neighbour – could host a
habitable planet“, says Duncan Wright of the University of
New South Wales and lead author of a paper describing the
discovery in a forthcoming issue of Astrophysical Journal
Letters.
009_News_Feb16FIN.indd 16 11/01/2016 19:29
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017_U2Gad_feb16.indd 17 11/01/2016 15:19
18. For news updates, visit www.astronomynow.com
18 | Astronomy Now | February 2016
NEWS UPDATE
B
lack holes can grow no larger than 50 billion
times the mass of the Sun through the process
of swallowing gas, according to Professor
Andrew King of the University of Leicester.
The supermassive black hole at the centre of a
galaxy grows most rapidly when it is consuming vast
amounts of gas from a doughnut-shaped disc, or torus,
around it. The more massive the disc, the hotter it
becomes and we see these discs as quasars. When the
inner regions of the disc lose energy through friction
and gravitational tides, the gas can spiral into the
black hole. However, these discs of gas are inherently
unstable and they often collapse to form stars.
King found that a black hole could grow to 50
billion solar masses through the process of accretion
before its gravitational tides were sufficient to destroy
the disc. Without a disc, the black hole cannot grow
any further from accretion, only through merging
with stars or another black hole, neither of which
requires a disc.
“The significance of this discovery is that
astronomers have found black holes of almost the
maximum mass, by observing the huge amount of
radiation given off by the gas disc as it falls in”, says
King, whose work is to be published in a forthcoming
issue of Monthly Notices of the Royal Astronomical
Society. “The mass limit means that this procedure
should not turn up any masses much bigger than
those we know, because there would not be a
luminous disc.”
Meanwhile, NASA’s NuSTAR X-ray telescope
has peered into the gas torus around a black hole for
Gravitational lens makes supernova reappear
Black holes reach their mass limit
Thanks to the lensing power of a
massive galaxy cluster, astronomers
have for the first time been able to
predict the appearance of a supernova.
In November 2004, the Hubble
Space Telescope spotted multiple
lensed images of the same supernova,
produced by dense concentrations of
foreground matter warping space and
bending the light of the supernova
along different paths. The galaxy
cluster doing the lensing – MACS
J1149.5+2223 – is located five billion
light years away, whereas photons from
the supernova have been travelling for
ten billion years.
The different paths taken by the
light of the supernova each incur a
different time delay. By modelling
the distribution of mass in the cluster,
astronomers led by Tommaso Treu
of the University of California, Los
Angeles, predicted that another
image would appear by the end of
last year. Sure enough, the supernova
reappeared on 11 December 2015.
Alas, says Treu, the resolution of the
Hubble image is not sufficient to reveal
the progenitor star, so we cannot
determine the behaviour of the star in
the run-up to its destruction.
The discovery, however, might
have greater cosmological importance.
In 1964 Norwegian astronomer Sjur
Refsdal predicted that time-delayed
images of supernovae could be seen
through gravitational lenses, and
hence this exploding star has been
nicknamed the Refsdal supernova.
Refsdal suggested that by accurately
calculating the time delay between
images, it might be possible to measure
the expansion of the Universe.
“We can in principle use the
supernova to measure the expansion
rate of the Universe, once we have
measured the time delay“, Treu tells
Astronomy Now. “We’ll have to monitor
for several months – possibly a whole
year – before we can determine the
the first time and found it to be clumpy. Along with
the European Space Agency’s XMM-Newton space
telescope, NuSTAR observed the disc around the
black hole at the centre of the galaxy NGC 1068. The
findings, to be published in the 11 February 2016
issue of Monthly Notices of the Royal Astronomical Society,
might explain why some black holes are obscured by
their disc, while others are not. The aim is now to
figure out what is causing the gas to form clumps: is it
turbulence in the disc, or does material rain onto the
disc in clumps from outside?
Black holes can
grow to 50 billion
solar masses before
their surrounding
disc of clumpy gas is
destroyed. Image:
ESA/V Beckmann
(NASA GSFC).
time delay precisely. However, whether the measurement
of the expansion rate of the Universe will be sufficiently
precise to be interesting will depend on how accurately we
can measure the time delay and how accurate we can make
the lens models.”
The multiple paths
of the supernova’s
light as it passes
through the galaxy
cluster on its way
towards Earth.
Image: NASA/ESA.
009_News_Feb16FIN.indd 18 11/01/2016 19:29
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019_baaderad_feb16.indd 19 11/01/2016 15:21
20. For news updates, visit www.astronomynow.com
20 | Astronomy Now | February 2016
B
asaltic rocks investigated by China’s Chang’e-3 mission to the
Moon have been found to sport a slightly different mineralogical
composition compared to the Moon rocks brought back to Earth
by the Apollo astronauts. The findings indicate that the interior of the
Moon may not be as uniform as previously thought.
Chang’e-3 landed in the northern part of Mare Imbrium in 2013.
Imbrium is one of the younger lunar floodplains, at around three billion
years old. Its surface is smooth, with a thinner layer of crumbly regolith
(dirt and dust) on top of the bedrock, which has proved crucial. Normally
regolith is so thick and filled with debris that it hides the bedrock and
makes it difficult to discern from orbit. Chang’e-3 and its little rover, Yutu,
were able to sample the bedrock directly.
“We now have ‘ground truth’ for our remote sensing, a well-
characterised sample in a key location”, says Bradley Jolliff of Washington
University, who participated in a collaboration between Chinese and
American scientists to publish the findings in the 22 December 2015 issue
of the journal Nature Communications. “We see the same signal from orbit
in other places, so we now know that those other places probably have
similar basalts.”
The difference between the Imbrium basalts and basaltic rocks from
other regions on the Moon is the concentration of titanium. The Apollo
and Soviet Luna missions returned rocks to Earth from older lava plains
on the Moon that had either very high or very low amounts of titanium,
whereas the rocks that Chang’e-3 inspected have medium concentrations
and were also richer in iron. The relative titanium abundances highlight
differences in the mantle where the lava originated from.
“The diversity tells us that the Moon’s upper mantle is much less
uniform in composition than the Earth’s”, says Jolliff. “We’re still trying
to figure out exactly how this happened. Possibly there were big impacts
during the magma ocean stage that disrupted the mantle’s formation.”
NASA’s Curiosity rover has detected surprisingly high
concentrations of silica in rocks embedded within
geological layers up the flanks of the five-kilometre tall
Mount Sharp.
Silica is a chemical compound of oxidised silicon
and the levels of silica discovered by Curiosity are much
higher than has been seen anywhere else on Mars so far.
In some cases, Curiosity discovered rocks that were nine-
tenths pure silica.
“You can boost the concentration of silica either
by leaching away other ingredients while leaving silica
behind, or by bringing in silica from somewhere else“,
says Albert Yen, who is a Curiosity science team member
at NASA’s Jet Propulsion Laboratory (JPL). “Either of
these processes involves water.”
Acidic water could have carried other materials
away, leaving behind the silica. Alternatively, alkaline or
neutral pH water could have deposited dissolved silica
when the water evaporated. Discovering which was the
case will tell us more about the history and nature of
water on ancient Mars.
Intriguingly, one of the silica-rich rocks investigated
by Curiosity was found to contain its silica in a mineral
called tridymite. This mineral is rare on Earth, forming in
high temperature volcanic or metamorphic rocks (which
are ordinary rocks that change their chemical or physical
properties when exposed to high temperatures), but
tridymite has never been found on Mars until now.
Volcanic rock can evolve to become rich in silica, but the
silica-rich rocks that Curiosity has found are thought to
have been laid down on a lake bed billions of years ago.
It suggests that volcanism may have been the root cause
behind the silica, but that subsequent water action
resulted in the concentrations of silica that we see today.
Silicon Mars: was
its water acidic
or alkaline?
A view of geological layers on the flank of Mount Sharp.
Image: NASA/JPL–Caltech/MSSS.
Volcanic rocks reveal
the Moon’s uneven
interior
A artist’s impression of
Chang’e-3’s rover,Yutu,
on the ground at Mare
Imbrium. Image: CNSA.
009_News_Feb16FIN.indd 20 11/01/2016 19:29
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23. For news updates, visit www.astronomynow.com
February 2016 | Astronomy Now | 23
NEWS UPDATE
R
aging storms are known to be common in the atmospheres of gas giant
planets and nearly-stars called brown dwarfs, but a joint effort by NASA’s
Kepler and Spitzer space telescopes has spotted a storm on a star.
Admittedly, the star in question is a timid one. Called W1906+40, it
belongs to a class of stars known as L-dwarfs. Although some L-dwarfs are
brown dwarfs, others like W1906+40 are thought to be proper stars that
Below: a trio of bow
shocks imaged by
WISE and the Spitzer
SpaceTelescope.
The infrared images
are presented in
false colour. Images:
NASA/JPL–Caltech/
University of
Wyoming.
Spitzer sees stormy star
fuse hydrogen in their cores, judging by their age and
temperature. Still, W1906+40 is fairly cool for a star,
with a temperature on its photosphere (the star’s visible
‘surface’) of just 2,038 degrees Celsius. For comparison,
the Sun’s photosphere is about 5,500 degrees Celsius.
“The star is the size of Jupiter and its storm is the
size of Jupiter’s Great Red Spot”, says John Gizis of
the University of Delaware, USA, who is lead author
of a study describing the enormous storm in the 10
November issue of the The Astrophysical Journal.
The star itself was discovered by NASA’s Wide-field
Infrared Survey Explorer (WISE) in 2011, lying around
53 light years away. It was not until later that Gizis
and his team realised that W1906+40 was actually in
the field of view of the Kepler Space Telescope, which
originally stared at a patch of sky in the constellations
of Cygnus and Lyra. The storm is so large that when
it rotates into view every nine hours it causes the star’s
light to dip. Kepler detected this dip, but originally
scientists interpreted it as starspot. It was only when
the Spitzer Space Telescope followed up that it was
revealed to be a cloudy storm laden with mineral grains
that has persisted for at least two years now. If you
could travel to W1906+40 in person, you would see the
storm as a dark spot close to the star’s polar regions.
It is the best evidence yet that cool stars can have
storms and dark spots like giant planets and brown
dwarfs, further blurring the lines between these low
mass objects.
An artist’s
impression of the
star with the dark,
churning storm.
Image: NASA/JPL–
Caltech.
Speeding stars caught ramming through space
Like cosmic speed cameras, NASA’s infrared Spitzer and WISE telescopes have
caught hundreds of stars racing breakneck through the Galaxy, piling up gas in
front of them in what are called‘bow shocks’.
Some stars lead frenetic lives, reaching velocities of around 86,400 kilometres
per hour. They arrive at these tremendous speeds following events in their past
that propel them on their way.
“Some stars get the boot when their companion star explodes in a supernova,
and others can get kicked out of crowded star clusters“, says William Chick of the
University of Wyoming, who led the research.
As they move through the Galaxy they are shielded by a magnetic buffer
blown by their stellar winds, much like our Sun’s solar wind creates the magnetic
heliosphere surrounding the Solar System. The hotter and more massive a star, the
stronger its stellar winds and the larger its magnetic bubble. Coupled with how fast
a star is moving, the magnetic bubble can plough through gas in the interstellar
medium that lies in the star’s path, creating a bow shock of compressed gas ahead
of it, like how a boat pushing through water creates a wave in front of it.
These bow shocks are warm, so
they glow brightly in infrared light.
Chick and his colleagues scoured
archival data from the Spitzer Space
Telescope and the Wide-field Infrared
Survey Explorer (WISE) to search for
the best bow shock candidates. They
found 200 and, when they followed
up on 80 of the most promising, they
discovered fast-moving massive stars
inside most of them. The size of the
bow shocks can provide information on
things as diverse as the density of the
interstellar medium and the magnetic
field strength of the star.
Meanwhile, a group of Argentinian
astronomers is tackling the problem
from the opposite direction. Led by
Cintia Peri of the Argentine Institute of
Radio Astronomy, they are first finding
the speedy stars and then trying to
detect a bow shock.
“WISE and Spitzer have given us the
best images of bow shocks so far“, says
Peri. “In many cases, bow shocks that
looked very diffuse before, can now be
resolved, and, moreover, we can see
some new details of the structures.”
009_News_Feb16FIN.indd 23 11/01/2016 19:30
25. For news updates, visit www.astronomynow.com
February 2016 | Astronomy Now | 25
NEWS UPDATE
by Alan LongstaffTALKINGpoint
Speculation or science?
S
tring theory and the multiverse dominate
modern cosmology, but are they science
or just speculative hypotheses that
have come to be exempted from experimental
verification? This was the subject of a workshop
held at the Ludwig Maximilian University in
Munich, Germany, in December 2015. It is a
debate that has been a long time coming. For
over a decade there has been increasing unease
amongst some scientists about the speculative
character of some ideas in physics. These
concerns came to a head in the 18 December
2014 issue of the prestigious journal Nature
when two internationally renowned scientists –
cosmologist George Ellis of the University of
Cape Town and astronomer Joseph Silk of Johns
Hopkins University, Baltimore – issued a clarion
call to ‘defend the integrity of physics’. They
were responding to the view of some researchers
that if a theory is sufficiently elegant and
explanatory it need not be tested experimentally.
This breaks with the generally accepted view of
philosopher Karl Popper that for a theory to be
scientific it has to be falsifiable; there has to be
some experiment or observation that can show it
is wrong. The workshop came about as a result
of their Nature article. What are the issues?
For Ellis and Silk, both string theory and the
multiverse are ideas that cannot be refuted, i.e.
they fail Popper’s test. They distinguish these
from theories ‘that relate directly to the real
world and are testable through observations’,
such as dark matter and dark energy. String
theory is seductive because it seems to offer
a way to unify gravity with quantum theory
and the mathematics is beautiful. However,
conclusions arising from mathematics need
not mirror what happens in reality, as we know
from Steady State Theory. Their point is that
the ‘strings’ of string theory are far too small to
be detected currently and the theory relies on
dimensions we can never observe.
Refuting the multiverse?
The multiverse idea comes in a couple of
flavours; the kaleidoscope version requires an
unfathomable number (10500
) of other universes
to exist simply to explain why our Universe has
values for physical constants that allow us to
exist. The ‘many worlds’ version branches into
parallel universes every time an observation
forces a quantum system to make a choice (think
Schrödinger; dead cat/live cat) and is but one
of several interpretations of the enigmatic machinations of quantum mechanics.
However, no one can dream up a way to refute the existence of these other
universes, even in principle. A counterargument that might work for string theory
is that just because a theory cannot be falsified today does not mean that it can
never be. After all, science lived happily with atoms and electrons long before they
could be seen directly.
Some have attempted to redefine what is meant by a scientific theory.
Cosmologist Sean Carroll regards falsifiability as a ‘blunt instrument’, arguing that
a theory is scientific if it says something unambiguous about how reality works
and explains the data. The difficulty here is that often there are several equally
good ways to account for the data, so how do we choose between them? A more
worrying trend is that some string theorists cite internal consistency as a way of
validating a theory, or even the lack of credible alternatives, i.e. if it’s the only
game in town, it’s probably right.
Now before you spill your coffee, it’s worth looking at the history of black
holes. These objects are theoretical. No one has ever seen a black hole directly, i.e.
the ‘shadow’ of the hole on the accretion disc as depicted in the film Interstellar.
Yet black holes are pretty much accepted by the astronomical community to
account for phenomena – e.g. gravitational effects, quasars – that we cannot
explain in any other way.
Unsurprisingly the ‘only game in town’ argument about string theory
doesn’t cut ice with researchers such as Lee Smolin of the Perimeter Institute
for Theoretical Physics in Canada and Carlo Rovelli, Aix-Marseille University,
France, who are exploring another idea, loop quantum gravity, which they argue
makes testable predictions.
If theoretical physics loses its empirical moorings, this will provide greater
purchase for pseudoscientists to peddle their nonsense. Now is not a good time
to damage public confidence in science, when climate change and the theory of
evolution are being denied by some politicians and religious fundamentalists,
argue Ellis and Silk. The workshop probably didn’t change opinions, but at least it
has kick-started a discussion on what is meant by the scientific method.
Dr Alan Longstaff is a regular contributor to Astronomy Now.
An artist’s take
on the multiverse
– are theories of
parallel universes
scientific? AN
graphic by Ben
Gilliland.
009_News_Feb16FIN.indd 25 11/01/2016 19:30
26. For news updates, visit www.astronomynow.com
26 | Astronomy Now | February 2016
NEWS UPDATE
SpaceX made big strides in the
company’s quest to drastically cut the
cost of spaceflight in December with
the successful landing of a 15-story
Falcon 9 rocket booster at Cape
Canaveral on 21 December.
The California-based launch
provider delivered 11 commercial data
relay satellites into low Earth orbit
for Orbcomm, a US communications
company, as the Falcon 9’s first stage
manoeuvred back towards its Cape
Canaveral launch site a few minutes
after lift-off. The booster reignited one
of its rocket engines to slow down and
descend vertically to a landing zone
about 10 kilometres south of the Falcon
9 launch pad.
The recovery of the booster is a
key step towarda making the Falcon
9 partially reusable, an objective
long desired by SpaceX’s billionaire
founder Elon Musk, who says the
cost of space transportation must
be reduced to achieve his vision of
colonising Mars. The Falcon 9 landing
came weeks after Blue Origin, a rival
space company founded by Amazon’s
Jeff Bezos, landed a suborbital rocket
in November, but that feat was on a
smaller scale than SpaceX’s rocket
recovery experiment.
SpaceX plans to test the used
Falcon 9 booster to see how much
refurbishment is required to fly the
rocket again. Musk hopes to reuse a
future Falcon 9 first stage this year.
NASA announced in December that
the InSight lander designed to detect
seismic activity on Mars will not be
ready for launch in March. The delay
means the probe will not launch before
May 2018, the next time Mars and Earth
are in the right positions in the Solar
System to make the interplanetary trip
possible. Managers blamed leaks in a
vacuum enclosure holding InSight’s
French-made seismometers.
The International Space Station
completed a crew rotation in
December, with three crewmen
returning to Earth and another trio of
residents blasting off to start a half-
year in orbit.
R u s s i a n c o s m o n a u t O l e g
Kononenko, NASA astronaut Kjell
Lindgren and Japanese flight engineer
Kimiya Yui landed in Kazakhstan on 11
December to wrap up more than 141
days in space. Four days later, British
astronaut Tim Peake, commander Yuri
Malenchenko and NASA flight engineer
SPACEFLIGHT NOWStephen Clark reports on the latest spaceflight news from Cape Canaveral. To find out more visit spaceflightnow.com.
Key moments in astronomy
A
ndrew Claude de la Cherois Crommelin was – as his
name does not immediately suggest – an Ulsterman.
Born on 6 February 1865 at Cushendun, County Antrim,
he was a descendent of Louis Crommelin. This seventeenth
century entrepreneur revitalised the Irish linen industry. Andrew
was to do much the same for cometary studies.
Educated at Marlborough and Trinity College, Cambridge,
even as a boy Crommelin was an enthusiastic astronomer.
There was never much doubt as to his chosen career: he joined
the Royal Observatory (RGO) in 1891, appointed as a ‘Second
Class Assistant’. Humble though the position sounds, it was
recognised as an entry point for young but exceptionally talented
astronomers. Such prestige perhaps compensated for the
wretched pay – a very mediocre £200 per year.
Initially, Crommelin’s work involved lunar and cometary
observations using the Greenwich Transit Circle,Airy’s Alt-azimuth
and the Sheepshanks Equatorial telescope.All were – at a kindly
assessment – approaching the end of their useful life. Yet they
introduced Andrew to the field he made his own.As a writer in The
Observatory in 1940 remarked,“to think of Crommelin was to be
reminded of comets and minor planets".The path to his greatest
achievement began in December 1906, when he read a paper to the
Royal Astronomical Society, pointing out that the best predictions
for the return of Halley’s comet varied by many years.Alongside
his colleague, Philip Cowell, he intensively researched previous
appearances, making extensive use of the latest observations of
asteroids and gravitational effects. Crommelin and Cowell’s work,
originally published in a series of papers between in 1907 and 1908,
predicted perihelion to within three days of the event.
Such accuracy was unprecedented, but their methods were so
exact that they rightly believed the error reflected the influence
of unknown, non-gravitational forces. These have since been
identified as gaseous emissions from the nucleus of the comet,
subtly diverting its course. Both authors were awarded the
Lindemann Prize of the Astronomische Gesellschaft and doctoral
degrees from Oxford University in recognition of their work.
Crommelin was director of the British Astronomical
Association’s comet section for many years and President of the
Royal Astronomical Society from 1929 to 1931. He was also an
avid observer of eclipses and was particularly pleased to have
served on the 1919 expedition to Brazil, which played a major
part in confirming Einstein’s General Theory of Relativity. A
still more unusual honour came years after his death. In 1929 he
identified four earlier comet discoveries as referring to a single
entity. This became knows as Comet Pons–Coggia–Winnecke–
Forbes. The name was so inconvenient that in 1948 it was
officially renamed Comet Crommelin.
In private life the astronomer was known as enormously
well-read and deeply religious: He originally intended to take
Anglican orders, but underwent a spiritual crisis in the year in
which he joined the RGO, becoming a member of the Roman
Catholic Church. Crommelin’s wife, Letitia, whom he married
in 1897, died in 1921, whilst his eldest son Claude and youngest
daughter Philomena were killed in a mountaineering accident in
1933. The astronomer died in an equally unexpected way, struck
by a motor cycle during the blackout on 20 September 1939.
Ian Seymour
Gravity and gas
Tim Kopra soared into space on a Soyuz rocket, reaching the
space station about six hours later.
Two more satellites joined Europe’s Galileo navigation system
with a launch from the European spaceport in French Guiana
on 17 December. The two new spacecraft are the eleventh
and twelfth satellites for the Galileo network, a civilian-run
analogue to the US military’s Global Positioning System,
which is to be fully operational by 2020.
Other launches in December included an Indian mission on
16 December with six satellites for Singapore, the launch of a
Russian–European communications satellite on 24 December
aboard a Proton rocket, and the 28 December lift-off of a
Chinese observatory fitted with a telescope to peer down at
Earth from geostationary orbit, a capability Chinese media
says will help track US aircraft carriers in the Asia–Pacific.
The first stage
of a SpaceX
Falcon 9 rocket
descends to a
landing pad at
Cape Canaveral
minutes after
launching with
11 commercial
communications
satellites.Image:
SpaceX.
009_News_Feb16FIN.indd 26 11/01/2016 19:30
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30. 30 | Astronomy Now | February 2016
TRIPPING THE LIGHT FANTASTIC
T
he aurora is one of nature’s most beautiful sights.
Shimmering curtains of light in the sky, dancing around the
Earth’s north and south magnetic poles, inspire wonder and
amazement in those who have witnessed them. However,
this phenomenon isn’t exclusive to Earth. Aurorae also occur
elsewhere in the Solar System where there are magnetic fields and
atmospheric gases to produce these marvellous lights.
Jupiter
If you thought the aurora on Earth was a sight to behold, wait till you
see what it looks like on the gas giants! Jupiter’s magnetic field is ten
times stronger than the Earth’s, so it’s not surprising that this planet
also has aurorae, and they are huge – Jupiter’s aurorae could engulf
the Earth many times over.
Unlike the Earth’s ephemeral and intermittent polar lights, these
thelight
fantastic
We are all held in awe by the beauty of the aurorae that dance in the skies of the Earth’s
northern and southern hemispheres, but these ethereal curtains of light aren’t unique to
our planet. Isadora Fontaine takes a trip around the Solar System’s auroral displays.
The Aurora Australis
observed from the
International Space
Station. Image credit:
William L. Stefanov,
NASA-JSC.
030_Aurora_Feb16FIN.indd 30 11/01/2016 11:47
31. February 2016 | Astronomy Now | 31
TRIPPING THE LIGHT FANTASTIC
Solar wind
Plasma Aurora
Magneticfie
ld
Electron
Electron
Proton
Alpha particle
(helium
nucleus)
Oxygen
molecule
• Aurorae are caused by the interaction between
charged particles from space, a magnetic field and
atmospheric gases.
• They are known as the Aurora Borealis, or
Northern Lights, when they occur above the Earth’s
north magnetic pole, and the Aurora Australis
(Southern Lights) when they occur above the south
magnetic pole.
• As the solar wind buffets the Earth’s magnetic
field, charged particles from the Sun and plasma
from our planet’s magnetosphere are flung into
the upper atmosphere, following magnetic field
lines towards the magnetic poles. These energetic
particles collide with molecules of atmospheric gas,
causing them to emit photons and thus giving rise
to the dazzling light show. Oxygen produces green
and red aurorae, while nitrogen produces purple
and blue light.
• The aurorae on Earth are most often seen in the
two ‘auroral ovals’ that encircle the north and
south magnetic poles, at high latitudes.
• Occasionally, during periods of high solar activity,
the aurora intensifies, producing more vivid
displays of light, and sometimes the auroral ovals
migrate temporarily to lower latitudes.
Whatisanaurora?
Graphic: Ben Gilliland
030_Aurora_Feb16FIN.indd 31 11/01/2016 11:47
32. 32 | Astronomy Now | February 2016
TRIPPING THE LIGHT FANTASTIC
the rotation of Jupiter’, states astronomer John Clarke from
Boston University. ‘Other moons can contribute, but Io’s
plasma dominates.’
As volcanoes on Io erupt, they release charged
particles into Jupiter’s magnetic field. These particles then
form a ring, or torus, of plasma stretching almost as far as
Saturn’s orbit. The volcanically active moon also causes
flares in the aurora, seen as bright spots that correspond
with Io’s orbit. These arise when streams of erupted
particles from Io interact directly with Jupiter’s atmosphere,
rather than just contributing to the plasma torus.
The other Galilean moons, icy Europa, Ganymede and
Callisto, might also deliver charged particles to Jupiter’s
plasma ring and cause flare-ups in its aurorae, but their
effect is less well understood.
Mars
It may come as a surprise for a planet without magnetic
poles, but Mars has its own aurorae. ESA’s Mars Express
and NASA’s MAVEN spacecraft have been observing
aurorae while in orbit around the red planet. These are
transient and rare events, but are boosted during solar
storms, which produce particularly energetic electrons to
trigger aurorae deep in Mars’ thin atmosphere.
‘In the case of Mars, there is no global magnetic field
and the aurora is observed in the southern hemisphere,
where high-elevation terrains have kept part of the
ancient magnetic field, before the dynamo effect (a
magnetic field generated by a liquid metallic core,
like that of the Earth), which sustained the global field,
vanished a long time ago’, states Jean-Claude Gerard
from the University of Liège, Belgium.
A particularly intense aurora was spotted by
aurorae are a permanent feature surrounding the Jovian
poles, glowing an eerie shade of red, owing to emissions
from Jupiter’s hydrogen-dominated atmosphere. They are
also caused not by the Sun, as on Earth, but by Jupiter’s
Galilean moons. (The solar wind plays a smaller part in
causing Jovian aurorae.)
‘The ultimate plasma source for most of Jupiter’s aurora
is the Io plasma torus, and the ultimate energy source is
Jupiter’s aurora, showing the influences of the Galilean moons.
Image credit: John T. Clarke (University of Michigan), ESA, NASA.
X-ray aurorae as observed by NASA’s Chandra X-ray Observatory overlaid on a
simultaneous optical image from the Hubble Space Telescope. Image credit: X-ray: NASA/
CXC/SwRI/R. Gladstone et al.; Optical: NASA/ESA/Hubble Heritage (AURA/STScI).
IO SPOT POLAR OVALS TRANSPOLAR EMISSIONS
EUROPA SPOTGANYMEDE SPOT
DAYSIDE AURORA
MAIN OVAL
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33. TRIPPING THE LIGHT FANTASTIC
MAVEN’s ultraviolet spectrograph in 2014, nicknamed
‘the Christmas Lights’ because they were spotted in late
December. This was a different, more diffuse type of
Martian aurora to the ones previously seen by Mars
Express. ‘This type of aurora is caused by energetic
solar wind electrons that are accelerated on their way
to Mars. When they arrive close to Mars, they follow
open magnetic field lines to precipitate and excite
the atmosphere’, states Arnaud Stiepen, also from
the University of Liège. This causes carbon dioxide
molecules in the atmosphere to emit photons, giving rise
to blue aurorae.
Gerard and Stiepen have tips for any future astronauts
wishing to observe the Martian aurora. ‘You would not
need to move to high latitude regions as on Earth, but
you should be located in the southern hemisphere, in a
specific longitude, to have a chance of seeing it. The
aurora would probably be seen as a blue luminous
arc extending east–west’, suggests Gerard. However,
if a solar flare triggers an auroral display such as the
‘Christmas Lights’ of 2014, Stiepen says ‘astronauts
anywhere on the planet would see the whole night sky
painted in blueish colours!’
Saturn
Not only does Saturn possess beautiful rings, it also has spectacular
aurorae. The phenomenon has been photographed in detail by
Hubble and Cassini in visible, ultraviolet and infrared wavelengths.
Saturn’s aurorae are thought to be caused mainly by the action
of the solar wind on the planet’s magnetic field. ‘I would say that
Saturn is intermediate between the Earth’s and Jupiter’s auroral
processes. In all our data thus far, Saturn’s aurorae have responded
every time there has been a large change in the solar wind’, states
Clarke. This drives a current of about 1 million amps through its
ionosphere that accelerates electrons at immense energies, causing
the atmosphere to glow. However, Sarah Badman from Lancaster
University suggests that at least one of Saturn’s moons also has an
influence on the aurora. ‘Enceladus, which has water-ice plumes
coming from its southern pole, sometimes produces an auroral spot
in Saturn’s atmosphere.’
‘Saturn’s aurorae are red, changing to pink and purple instead of
the most common green colour of Earth’s aurora’, Badman states.
As with Jupiter, excited hydrogen molecules in Saturn’s atmosphere
produce the red colour. Images of Saturn’s aurorae show
them to be blue or white, because they are taken at ultraviolet
wavelengths.
Like Earth, Saturn’s aurorae are sensitive to fluctuations as the
stream of particles from the Sun strengthens and weakens, and they
generally form in ovals around the magnetic poles. However, as
Badman states, ‘unlike on Earth, the aurora can also elongate into a
spiral shape because of Saturn’s rotation.’ While on Earth they tend
to last minutes or hours, aurorae on Saturn last for days, and are at
their brightest at dawn. As with Jupiter, Saturn’s polar lights are of
an impressive size. ‘You could fit more than four Earths inside one of
Saturn’s auroral ovals’, Badman adds.
Streams of charged particles
blasted from the Sun collide with
Saturn’s magnetic field, creating
an aurora on the planet’s south
pole. Unlike Earth’s relatively
short-lived auroras, Saturn’s
can last for days. In this Hubble
image the aurora appears blue,
but a Saturn-based observer
would see red flashes. Image
credit: NASA, ESA, J. Clarke
(Boston University), and Z.
Levay (STScI).
33
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34. 34 | Astronomy Now | February 2016
TRIPPING THE LIGHT FANTASTIC
An artist’s impression of MAVEN observing the
Martian aurora. Image: University of Colorado.
Composite images of Uranus, combining Hubble observations from 2011 of the
aurorae in visible and ultraviolet light, Voyager 2 images from 1986 in visible
light, and Gemini Observatory infrared observations from 2011 of Uranus’ faint
rings. Image: NASA, ESA, and L. Lamy (Observatory of Paris, CNRS, CNES).
Uranusand
Neptune
Images taken by the
Hubble Space Telescope
in 2011 show bright
spots in the atmosphere
of Uranus, which turned
out to be aurorae. These
images were taken during
a period of heightened
solar activity, showing
solar particles to be the
cause of these aurorae.
The bright spots on the
planet were located far
from its poles, since the
magnetic field of Uranus
is tilted at 59 degrees
from its spin axis.
Aurorae on Neptune
were first detected by
the Voyager 2 probe as
it passed by the planet
in 1989. Little is known
about Neptunian aurorae.
They occur over wide
areas of the planet rather
than just at the poles,
owing to the planet’s
complex magnetic field,
and they are also 200
times weaker than
aurorae on Earth.
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35. TRIPPING THE LIGHT FANTASTIC
35
stream of plasma from Jupiter and you have the
perfect recipe for northern and southern Lights.
One of the most interesting outcomes of
observing the aurora on Ganymede is that
it suggests the existence of a large, deep
ocean of liquid water under its thick ice crust.
Observations made with the Hubble Space
Telescope in 2015 showed that the deflections
caused by Jupiter on the moon’s magnetic field
were a lot smaller than expected, meaning
that something else is generating a secondary
magnetic field on Ganymede, the most likely
culprit being an electrically conductive ocean of
saltwater up to 330km deep, able to produce
a magnetic field of its own. The presence of
an ocean brings up the inevitable question
on whether this moon might have life forms
swimming in its subsurface waters. This has
made Ganymede a target for the future ESA
space mission Juice, due to launch in 2022,
which will analyse Jupiter’s large icy moons and
will be sent into orbit around Ganymede.
Venus
Like Mars, Venus does not have a
global magnetic field, but there is
evidence that it too has aurorae.
As the solar wind interacts with
Venus’ ionosphere, it produces a
magnetised ‘tail’ of charged particles
streaming away from the Sun, similar
to a comet’s tail.
‘On Earth, aurorae only occur
around the magnetic poles, but on
Venus they are observed across the
night side of the planet. The exact
mechanism for solar wind particles in
Venus’ tail to penetrate the night side
of Venus is as yet unknown, however
aurorae are only observed after solar
storms, particularly coronal mass
ejections’, states astronomer Candace
Grey of New Mexico State University
in Las Cruces.
One theory is that heightened
solar activity causes magnetic
reconnection, a process that sparks
aurorae on other planets, including
the Earth, to take place within Venus’
magnetised tail. The magnetic field
lines ‘snap’, propelling high-energy
particles into Venus’ atmosphere,
thereby producing green sky glows.
‘The bright green emissions observed
on Venus are due to excited oxygen
atoms’, Grey continues.
Ganymede
Aurorae outside the Earth are not
limited just to planets. Ganymede,
the largest moon in the Solar
System, is also the only moon with
a magnetosphere generated by a
metallic core in a manner similar to
that of the Earth’s magnetic field. In
addition to this, the moon also has a
thin atmosphere of oxygen. Add in a
Auroraebeyond
thesolarsystem
In July 2015, the first ‘exo-aurorae’ were
discovered, on a brown dwarf called LSR
J1835+3259. They were discovered using radio
observations by the Very Large Array in New
Mexico. They are 10,000 times more powerful
than any of the aurorae in our solar system, but
their cause is a mystery. They could indicate the
presence of planets orbiting LSR J1835+3259
producing plasma that interacts with the brown
dwarf’s magnetic field (in a similar manner to
the way plasma from Io sparks off aurorae on
Jupiter), or they might be produced by the rapid
rotation of the brown dwarf.
Aurorae have not yet been detected on exoplanets,
but there is no doubt that they exist and may be
detected with more advanced telescopes in the future.
The solar wind strikes Venus in this
illustration, perhaps hard enough to
spark aurorae. Image: C. Carreau/ ESA.
An artist’s concept of aurorae on Jupiter’s moon,
Ganymede based on observations by NASA’s Hubble
Space Telescope Image credit: ESA and G. Bacon (STScI).
Isadora Fontaine is a freelance science writer.
030_Aurora_Feb16FIN.indd 35 11/01/2016 11:47
36. Moravian Instruments
CCD Cameras Behind the Best Astrophotographs
Image on the background:
Part of the Cygnus mosaic by
Jean Claude Canonne
Philippe Bernhard
Didier Chaplain
Laurent Bourgon
Image stitched from 4 frames
taken with G4-16000 cameras
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