astronomy magazine october 2013

8/10/2019 Astronomy Magazine October 2013

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The worlds best-selling astronomy magazine

TOP 10EXOPLANETSOf nearly 1,000 distant planets found,we explore the most unusualp. 22

See COMET ISON

n Octoberp. 50

Capturing the Suns atomsp. 54

AND MORE!

OCTOBER

0 GREAT

all binocularights p. 58

Spice up imageswith Hydrogen-alphap. 60

Denkmeiersbinocularviewer testedp. 64

NEW RESULTS: Planck mission resets the universes age

www.Astronomy.com

In the past 20 years, astronohave discovered planets u

anything in our solar sy

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W

eve now reached

the month in

which Comet

ISON (C/2012

S1) will reallystart to brighten, presumably

becoming a naked-eye object

by months end. It seems like a

good time to look back on the

first Great Comet I ever saw,

Comet West (C/1975 V1).

Danish astronomer

Richard M. West found a

fuzzy object November 5,

1975, at the European South-

ern Observatorys facility in

La Silla, Chile. West (pro-

nounced vest) saw an objecthe described as between 14th

and 15th magnitude and with

a slight coma 2 to 3 arc-

minutes in diameter.

When Brian Marsden at

the Central Bureau for Astro-

nomical Telegrams received

word of the discovery and

calculated an orbit, he found

that the comet would become

bright by February 1976. So

was announced Comet West

(C/1975 V1).

The comet brightened

rapidly as it neared Earth and

the Sun. On November 25,

1975, Leo Boethin, living in

the Philippines, became the

first to spot West visually,

glowing faintly at magnitude

12.7 and with a tail measur-

ing just 4 arcminutes long.

On December 1, Comet West

became visible to Northern

Hemisphere observers, and

Tsutomu Seki, at the Geisei

Observatory in Japan, esti-

mated the magnitude at 12.5.

Comet Wests appearancebecame very bright in Febru-

ary 1976, when the comet

brightened to 4th magnitude

by mid-month and then dra-

matically grew more brilliant

during the next two weeks,

reaching magnitude 1.5 by

February 24. Close to perihe-

lion passage on the 25th,

observers spotted Comet

West in the daytime sky using

binoculars or telescopes.

Following perihelion, thecomet became visible to

naked-eye viewers once again

March 1. Prominent in the

early morning sky, Comet

West displayed a brilliant

nucleus with a reasonably

bright inner coma, both of

which could be seen well in

the twilit sky. The comets tail

stretched only about 2, but

the overall magnitude was

impressively bright at about

1. Over the following days,

the tail grew, however, to 10

on the 2nd and as much as

30 long by March 8.

On March 4, Comet West

made its closest approach to

Earth, and the comet was

visible to naked-eye observers

throughout the month. On

March 5, skywatchers armed

with telescopes noted that the

comets nucleus appeared to

be split into two parts, sepa-

rated by about 3 arcseconds.

Six days later, telescopic view-

ers saw the nucleus as four

distinct components, whichwere labeled with letters, as is

the custom. Components A,

B, and D remained gravita-

tionally bound and were vis-

ible for months, although

component C faded rapidly,

disappearing by March 25.

As the nucleus of Comet

West split apart, the comet

faded. By March 31, it glowed

at magnitude 4.7, keeping it a

naked-eye object, but the

brilliance of the comet wasgone. By early April, it

stretched 4 long. Late April

witnessed Comet West sink-

ing to the naked-eye limit

with merely a 1 tail. Yet ama-

teur and professional astrono-

mers continued to observe

Comet West with binoculars

and telescopes for two more

months, with many unusual

observations taking place in

May and June.

Lets hope that Comet

ISON stays together and gives

us a tremendous show. It will

have been a long time coming.

Yours truly,

David J. Eicher

Editor

My first

GreatComet

Comet West (C/1975 V1) photographed in the springof 1976. ESO


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CONTENTS

WWW.ASTRONOMY.COM 5

22 COVER STORYTop 10 exoplanetsAstronomers have discovered

nearly 1,000 planets orbitingother stars. Here we highlight 10

of them. RICHARD TALCOTT

28How Planck hasredefined the universeis new spacecra has mapped

the universes matter, refinedits composition and age, and

revealed thousands of radiosources. LIZ KRUESI

34Ask AstroSolar blemishes.

36The Sky this MonthUranus at its best.MARTIN RATCLIFFE AND

ALISTER LING

38StarDome and

Path of the PlanetsRICHARD TALCOTT;

ILLUSTRATIONS BY ROEN KELLY

44Whatmakes a

Great Comet?Slight tweaks in the celestialrecipe make a good comet great.JOSEP H MARC US

50Comet ISON brightensbefore dawnis celestial visitor approachesnaked-eye visibility.

RICHARD TALCOTT

54Order from chaos

Genesis samples thesolar windis NASA spacecra captured

and returned atoms from the Sunto Earth. What happened next

took recovery to a whole newlevel. MEENAKSHI WADHWA

5810 great autumnbinocular sightsHead outside to explore a nearby

galaxy, a stellar waterfall, and

more. PHIL HARRINGTON

60Spice up your imageswith Hydrogen-alphadataMake your images shine by add-

ing light through this narrow-band filter. ROD POMMIER

64AstronomytestsDenkmeiers Binotron-27High-quality optics and superbmechanics make this accessory awinner. MIKE REYNOLDS

COLUMNSStrange Universe 9BOB BERMAN

Secret Sky 12STEPHEN JAMES OMEARA

Observing Basics 16GLENN CHAPLE

Cosmic Imaging 66TONY HALLAS

Astro Sketching 68ERIKA RIX

QUANTUM GRAVITYSnapshot 7

Breakthrough 8

Astro News 10

IN EVERY ISSUELetters 9, 12, 66

Web Talk 20

New Products 67

Advertiser Index 71

Reader Gallery 72

Final Frontier 74

FEATURES

Astronomy(ISSN 0091-6358, USPS 531-350) is pub-lished monthly by Kalmbach Publishing Co., 21027Crossroads Circle, P. O. Box 1612, Waukesha, WI531871612. Periodicals postage paid at Waukesha,WI, and additional offices. POSTMASTER: Sendaddress changes to Astronomy, 21027 CrossroadsCircle, P. O. Box 1612, Waukesha, WI 531871612.Canada Publication Mail Agreement #40010760.

OCTOBER 2013VOL. 41, NO. 10

NewsThe latest

updates fromthe scienceand hobby

ReaderForums

Chat withastronomyenthusiasts

Year of theComet

Pictures andinformation on

Comet ISON

Ask AstroArchive

Answers to allof your cosmic

questions

ONLINEFAVORITES

Go towww.Astronomy.comfor info on the biggest news and

observing events, stunning photos,informative videos, and more.

VisitAstronomy.com/tocfor bonus material itsexclusive toAstronomymagazine subscribers.

28

50

ON THE COVERKepler 11b is a giant planet fourtimes as massive and twice the sizeof Earth. Orbiting 10 times closer toits star than Earths distance fromthe Sun, we see it from the scorchedsurface of one of its possiblesatellites.

Online Content Code: ASY1310Enter this code at: www.astronomy.com/code

to gain access to web-exclusive content


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CHRONIC FATIGUES HIDDEN CAUSEp. 12

Science, Technology, and The Future

Meet the Nobel laureates exploringthe universes biggest mysteryp. 38

POCKET-SIZE ROBOTS(THEY COULD SAVE YOUR LIFE)p. 56HOW THE OZONE LAYERBOUNCED BACKp. 14

ZOMBIES AND MUTANTS AND SPOCKSUMMER SCI-FI MOVIE PREVIEW

p. 22

EXPANDYOUR MIND.

Every issue ofDISCOVER delivers: The latest news, theories, and

research in the world of science

Compelling stories and breakthroughsin health, medicine, and the mind

Environmental issues and theirrelevance to daily life

Cutting-edge technology and itsimpact on our future

Thought-provoking articles fromaward-winning editors, opinion

makers, Nobel laureates, andrenegade scientists

Its where CURIOUS PEOPLE turn for the newsand stories that expand and enrich their world.

Take an exciting adventure

with DISCOVER magazine

as it reports captivatingdevelopments in science,

medicine, technology, and

the world around us.

Subscribe to DISCOVER online atDiscoverMagazine.com

or call1-800-829-9132

P20327

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$19.95


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QG

QUANTUMGRAVITY

EVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH . . .

WWW.ASTRONOMY.COM 7

SNAPSHOT

Comet ISONbegins itsbig showAfter months of waiting,we begin to see whetherISON will be a star.

The wait will soon be over.Comet ISON (C/2012 S1) will

shortly brighten to naked-eye

visibility. We should soon knowjust how brilliant this comet isgoing to be.

Comet fever will then grip theastronomy world when ISON

slinks across southern Leo andinto Virgo during the first week

of November. By then, the cometwill brighten to 6th magnitude.

ISON then should increase by amagnitude every few days and

will dazzle viewers who rise tosee it in the early morning hours,

perhaps 4 .. on into dawn.

By about November 25, thecomet will have become impres-sively bright, shining at negative

magnitudes in eastern Virgo.The 28th brings the comets peri-

helion, its closest point to theSun. ISON may then be as bright

as Venus, or as much as 100times brighter yet. If so, it will

outshine everything in the skysave for the Sun and the Moon.

David J. Eicher

HOT BYTES >>TRENDING

TO THE TOP

GASSY GALAXY

The Herschel infrared tele-scope mapped the ionizedcarbon in the Milky Waysplane and found that 30percent of our galaxysmolecular gas was hidden.

MINI STARBURST

A study suggests that theCats Paw Nebula (NGC6334) is converting 3,600Suns of gas into stars ev-ery million years, earningit a starburst nickname.

DISORDERED DISK

Some scientists say thatgaps in disks surroundingyoung stars may not resultfrom forming planets, butinstead from interactionsbetween gas and dust.

Comet ISON (C/2012 S1) was imaged April 10, 2013, with the Hubble Space Telescope.


8/808 ASTRONOMYt OC TOBER 2013

Inside thering of lightThrough most amateurtelescopes, the RingNebula (M57) in Lyraappears as a distinct ovalwith nothing inside. Butwhen you combine thelight-gathering power ofthe two 8.4-meter mirrorsof the Large BinocularTelescope in Arizona withthe exquisite resolutionof the Hubble Space Tele-scope, this view changesdramatically. The bluishlight of ionized helium,energized by ultravioletradiation spewing from the

white dwarf star that liesat dead center, floods therings interior. Meanwhile,faint reddish tendrils of gassurround the bright ring.M57 lies some 2,300 light-years from Earth, and itsmain ring spans roughly1 light-year. NASA/ESA/C. R. ODELLVANDERBILT UNIVERSITY

BREAKTHROUGH



Its been years since theStrange Universe column

spotlighted a star, any star.How hard is it to choose

one from among the 6,000naked-eye luminaries?

Its a piece of cake. Most starsare dim and cursed with desig-

nations like HD 140283 or

Zubenelgenubi. Only a handfulare brilliant and have popularnames. Of them, just one floats

directly overhead at this time ofyear. So its automatic. Vega

(Alpha [] Lyrae) selects itself.Of all bright stars, Vega

boasts the shortest name andone of the most familiar. Yet its

routinely mispronounced.Thats because few know this

phonetics tip: Star names aresimple transliterations from

their original language. Youusually should pronounce them

as spelled. Rigel is really RY-jl,Spica is really SPY-kah, and

Vega is really VEE-gah. Noneed to add a Latin twist

even if thats how Jodie Fosterbewilderingly said it in the

movie Contact.Vega was, until the 19th cen-

tury, pronounced WEE-gah andeven spelled Wega in some

antique astronomy books. Itderives from Arabic and means

a swooping eagle. It also wasan eagle to the ancient Indians

and a vulture to the Egyptians.A bird. Dont ever let a friend

turn it into a cigar by sayingVAY-gah, even if one or two

criminally incompetent diction-aries list it that way.

Look overhead just as nightfalls. From most of the United

States, Vega is the only brightstar that ascends to within a few

degrees of the exact zenith. (Its

straight up from the nationscapital.) Shining at a steady

magnitude 0, Vega serves asthe standard candle that the

worldwide astronomical com-munity used to calibrate the

brightness of everything else inthe universe. Like the French

bar of platinum once used todefine the meter, Vega func-

tions as the skys reference pointfor the magnitude system. Its

an ideal choice because it dis-plays no flickering or variability,

despite years of controversyabout this. Moreover, its a sin-

gle star like the Sun instead of abinary like so many others.

But its still not quite a monu-ment to normalcy. In the 1990s,

a team of Canadian astronomers

announced that Vega, like a

fortune-cookie writer, exhibits

bizarre peculiarities. It spinscrazily in 12 hours, compared to

a month for our Sun, despitebeing nearly three times larger.

If it rotated just 18 percentfaster, it would break apart.

Moreover, its pole of rotation

is pointed straight towardEarth, give or take a fewdegrees. This means that any

Vegans (if any organism couldever really live on a star) look-

ing skyward would see our Sunas its north star!

Some 12,000 years from now,well return the favor. Vega peri-

odically becomes our pole staras Earths axis wobbles through

its 26-millennium precession.

Brightest of all our planetsnorth stars, it nonetheless

misses the celestial stationarypoint by some 4. So it never

achieves the visual glued-in-place appearance of the current

award-winner, Polaris.Vega has enjoyed more than

15 minutes of fame. It was thefirst star to be photographed

a feat attained at the exact mid-point of the 19th century, a

whopping 163 years ago. It was

also the first to have its spectrumtaken and, for those who own a

star spectroscope, displays a gor-geous mlange of reds, greens,

and blues in equal amounts,crossed by prominent dark

Balmer lines of hydrogen. Float-ing a mere 25 light-years from

us, Vega is a heavyweight withmore than twice our Suns mass

and 36 times its luminosity.Members of a major vegetar-

ian subculture call themselvesvegans, but no one knows if the

cuisine on Vega is truly meat-less. In any case, vegan ances-

tors likely did not hail fromthere. Despite being encircled

by a dusty disk with a stronginfrared signature that some

astronomers have interpreted as

evidence of a planetary system,actual life is implausible be-

cause of the stars youth, lessthan one-tenth the age of Earth

and our Sun.As if this werent enough to

keep us interested, Vega marksthe approximate direction we

travel toward in space. As ourentire starry neighborhood par-

ticipates in the Milky Ways

grand rotation, we do a little9-mile-per-second (14 km/s)sideslip in Vegas general direc-

tion. In a cosmos where red-shifts are as common as tattoos,

this diamond at the zenith dis-plays a blueshift. Its heading

our way.So enjoy nightfalls overhead

chess game as this seasonsbrightest stars zoom off in dif-

ferent directions. As the centu-ries pass, orange Arcturus in the

west will totally vanish from

sight while Vega grows everbrighter. Some 200 millenniahence, it will enrapture our

descendants as the skys mostbrilliant star. Celebrated even

more than it is today, Vega willretain that honor for the next

quarter-million years.

STRANGEUNIVERSE

Celebrate one of the skys most familiar luminaries.

B Y B O B B E R M A N

The

vegetarian star

FROM OUR INBOX

BROWSE THE STRANGE UNIVERSE ARCHIVE AT www.Astronomy.com/Berman.

Contact me aboutmy strange universe by visiting

http://skymanbob.com.

IN A COSMOS WHERE REDSHIFTS ARE ASCOMMON AS TATTOOS, THIS DIAMONDAT THE ZENITH DISPLAYS A BLUESHIFT.

Earning respectI have never written a letter to a magazine editor before, but after

reading The life and times of Al Nagler by Michael E. Bakich

(April 2013), I felt compelled to do so.Recently, I had called Tele Vue Optics customer service

regarding the cleaning and inspection of my 2.5mm Nagler eye-piece after a neighbor had inadvertently pressed his eye into it. I

began by telling the story to a Tele Vue representative about theexceptional seeing that night that drew a crowd and led to the

incident. Al must have been close by and was intrigued by thestory. After some 20 or 30 minutes of speaking with him, I felt

as though I was one of his friends. It was an experience I willnever forget. He not only received my repeat business, but he also

earned my respect. Brian Howe,Petersburg, Pennsylvania

We welcome your comments at AstronomyLetters, P. O. Box 1612,

Waukesha, WI 53187; or email to [email protected]. Please

include your name, city, state, and country. Letters may be edited for

space and clarity.

QUANTUMGRAVITY


10/80

ASTRONEWS

38days25days

31days

20 days37

days

37days

45days

23days

18

32days

28days

24days

7SCOR

PIUS

AQUARIUS

CAPRICORNUS

LIBRA

VIRGO

SAGITTARIUS

OPHIUCHUS

LEO

CANCER

GEMINI

TAURUS

ARIES

PISCES

FASTFACT

10 ASTRONOMY t OC TOBER 2013

CONKED COLOSSUS. The supermassive black hole in NGC 253 seems to have fallen asleep in the past decade eventhough the galaxy is actively forming stars, say astronomers in the July 10 issue of The Astrophysical Journal.

BRIEFCASE

ON THE REBOUND

Some of the light from Supernova 2009ig, the brightestof that year, bounced off material surrounding the

exploded star, suggesting the star broke apart because acompanion donated too much mass. The scattered radia-tion arrived at Earth the year after scientists observed the

initial detonation, showing up as a delayed light echo,the research team reported June 6 at the 222nd Ameri-

can Astronomical Society conference in Indianapolis.

tBOOMING BLACK HOLES

Black holes are responsible for 20 percent of the cosmicinfrared background light from a time when structure

first emerged from cosmic soup says a study in theMay 20 issue of The Astrophysical Journal. Astronomers

compared X-ray maps to infrared maps to find theseearly black holes, the only objects that appear as hot

spots on both.

tDISTANCE DETERMINATION

Scientists pinned down the distance to a pulsar 30 per-cent more accurately than their previous record. Using

the Very Long Baseline Array, they measured the objects

parallax how its position changed relative to back-ground objects as Earth moved in its orbit. With precise

measurements like this one, reported in the June 20 issueof The Astrophysical Journal, scientists will be better able

to characterize gravitational waves. S. S.

25 years agoinAstronomyIn the October 1988issue ofAstronomy, Ger-rit L. Verschuur pennedWill Solar Max beSaved? about a Sun-observing space tele-scope. The SolarMaximum Missions(SMM) orbit would takeit crashing back to Earth

in December of that yearwithout intervention.Verschuur argued for

saving the craft, whichwas the only observa-tory of its kind at thetime: A decision at thehighest level is requiredto allocate the $25 mil-lion for a shuttle missionto prolong the lifetimeof a spacecraft. Unfortu-nately, SMM fell out ofits orbit in a shower offlaming metal at theend of the year.

10 years agoinAstronomyIn the October 2003issue, Michael Carroll bidfarewell to another sci-entific spacecraft in Thelong goodbye. The ail-ing Galileo had studiedthe Jupiter system andwas on a collision coursewith the planet.

Galileo has weath-

ered a host of hardwareand natural obstacles,wrote Carroll. Projectmanager Eilene Theiligsaid, There is sadnessfor the final farewell, butat the same time, theresa sense of celebrationfor what the missionand project have done.Currently, NASAs Junospacecraft is on its wayto the largest planet; itwill be the first to visitsince Galileos violentdeparture. S. S.

HOW LONG IS

THE SUN IN THAT

CONSTELLATION?

T

he recently disabled Kepler telescopehas revolutionized exoplanet science.

However, a new study may change

conclusions scientists make fromKeplers observations because it suggeststhe stars and thus the planets are

larger than previously thought, accordingto a presentation June 4 at the 222nd meet-

ing of the American Astronomical Societyin Indianapolis.

Astronomers used the Kitt Peak NationalObservatory Mayall 4-Meter Telescope in

Arizona to gather spectra from a subset ofKeplers stars. Spectra show light divided

into its component wavelengths, tellingscientists about not just brightness but also

composition, temperature, and size.Most of the stars we observed are

slightly larger than previously thought, andone-quarter of them are at least 35 percent

larger, says lead scientist Mark Everett of theNational Optical Astronomy Observatory.

Any planets orbiting these stars must belarger and hotter as well.

Kepler watches for the telltale dip in a

stars brightness that means a planet may bepassing in front and blocking some of itslight, and astronomers use the specifics of

this transit to peg the planets size. If thesize of the star is incorrect, the calculated

size of the planet will be, too. According tothe new results, Keplers fruits may need to

be re-peeled. These new results reduce thenumber of candidate Earth-size planet ana-

logs, continues Everett.Although scientists might not have come

as close to finding an Earth-like planet asthey thought, the more data they combine,

the smaller the planets they can find. Fat-tening up the stars simply means that

astronomers may have to searcher harderand longer. Luckily for them, half of

Keplers observations remain untouchedon discs. Sarah Scoles

EXOPLANETS UNDERESTIMATED?

SIZE SHIFT.According to newobservations, sci-entists may haveunderestimatedthe girth of thestars in the Keplerfield. This changemeans planets like

Kepler 62f, whichscientists thoughtwas just 40 percentlarger than Earth,are even bigger.NASA/AMES/JPLCALTECH

SIGN OF THE TIMES.According to the

traditional horoscope, the Sun spendseither 30 or 31 days in each sign of thezodiac. But astrologers based the signson the constellations that surroundthe Suns path through the stars.The actual time the Sun spends ineach of those star patterns variesgreatly. And notice the extraconstellation astrologers havenever taken into account Ophiuchus the Serpent-bearer.The Sun spends 18 days travel-ing through it compared to onlyseven in Scorpius. ASTRONOMY: MICHAELE. BAKICH AND ROEN KELLY

Virgo is the largest zodiacal constellationand the second-largest star pattern over-all. Only Hydra is larger (by 0.6 percent).


11/80

ASTRONEWS

WWW.ASTRONOMY.COM 11

Swift takes glamour shots of the Magellanic Clouds

Scientists have struggled to piecetogether planet formation how dustparticles just millionths of a meter acrosseventually grow to worlds thousands ofkilometers wide. Simulations show thatparticles can collide with others andbreak apart or spiral into their star andthus never get big enough. But a newobservation of the young star systemOphiuchus IRS 48, some 390 light-yearsfrom Earth, may shed light on the com-plicated process of planet formation.

A disk of evenly distributed gas andsmall dust grains each about 50 mil-lionths of a meter surrounds the star;this disk also contains a thick gap where

scientist think a 10-Jupiter-mass planetmight be forming and clearing a path.But when they used the Atacama LargeMillimeter/submillimeter Array (ALMA)to look at larger dust grains, they founda crescent-shaped region of millimeter-sized grains that extends about one-third of the way around the star. Thisarea lies between 45 and 80 astronomi-cal units (1 astronomical unit equals the

average distance between Earth and theSun) from Oph IRS 48.

The team, led by Nienke van der Marelof Leiden Observatory in the Netherlands,suggests in the June 7 issue of Sciencethat this newly imaged area is actually adust trap a cavity where turbulencefrom the planet can collect and grow thelarger dust grains. Given the regions dis-tance from its star, the scientists think itmay be a holding compartment forfuture comets. Liz Kruesi

QUICK TAKES

SUCCESSFUL

SUPERNOVA

Scientists from the Max PlanckInstitute for Astrophysics com-pleted the most complex 3-D

simulations to date of howsupernovae explode and pro-

duce neutron stars. Their studyappeared in the June 10 issue

of The Astrophysical Journal.

tTRIUMPHANT SCOPE

Scientists announced June 4 atthe American Astronomical

Society meeting in Indianapolisthe discovery of a Saturn-sizedgas-giant exoplanet, KELT-6b,

some 700 light-years awayusing a 1.6-inch-wide (4.2 cen-timeters) automatic telescope.

tTMT FUNDING

The Japanese parliamentpassed a 2013 budget May 15

with 1,244 million yen (approx-imately $12.2 million U.S.) tocontribute to the proposed

Thirty Meter Telescope (TMT).

tGOODNIGHT, GALEX

NASA decommissioned its Gal-axy Evolution Explorer (GALEX)at 12:09 P.M. PDT June 28 after

a decade of observing theultraviolet universe.

tSOLAR STUDY

The balloon-borne solar experi-ment Sunrise II lifted off June 12for its journey lasting five days

and seven hours. It traveledaround the North Pole at an alti-tude of 22 miles (35 kilometers).

tWEIGHTY

WHITE DWARF

Astronomers report in the July1 issue of The Astrophysical

Journal Letterstheir observa-tion of pulsations from the

most massive white dwarf starfound to date, GD 518, with a

mass 1.2 times our Suns.

tSPYING THE SUN

On June 27, NASA launchedits Interface Region Imaging

Spectrograph to learn how theSuns material moves, gathers

energy, and heats up as it trav-els through the solar atmo-

sphere and into the Suns wind.

tACTIVE CENTER

Astronomers found dust aboveand below the doughnut-

shaped structure expected tosurround galaxy NGC 3783scentral supermassive black

hole. They suggest in the July10 issue of The AstrophysicalJournalthat the black holes

wind blows away dust. L. K.

CLOUDY SKIES.Youve never seen the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, quite like this. This 160-megapixelimage shows ultraviolet (UV) light from nearly 1 million separate objects. Astronomers at NASA and Pennsylvania State University in UniversityPark used the Swift space telescope to map the high-energy radiation that comes from high-powered, hot stars and star-forming regions in theLMC and the Small Magellanic Cloud, which boasted its own 250,000 UV sources. Scientists stitched thousands of images together to make glam-our shots of both galaxies, which NASA released June 3. S. S.

DELICATE DWARF. According to a June 10 report in The Astrophysical Journal, Segue 2 has a mass 150,000 times that of theSun thats nearly 10 million times lighter than the Milky Way and makes the galaxy the least massive one yet measured.

ALMA imagespossiblemissing link

NASA/SWIFT/S.

IMMLERGODDARDANDM.

SIEGEL

PENNSTATE

FORMING ROCKS.The young star OphiuchusIRS 48 has a surrounding disk of gas and dust, butlarger dust particles appear to congregate in aregion extending only about one-third of the wayaround the stars lower portion, as shown in thisartists illustration. ESO/L. CALADA

DUST TRAP.Observations suggestthe ring of material around OphiuchusIRS 48 has a holding cavity for larger,millimeter-sized dust particles (green),whereas finer, micron-sized dust parti-cles circle the entire star.

ALMAESO/NAO

J/NRAO/NIENKEVANDERMAREL


12/80


13/80

ASTRONEWS

Extra

Sun

Earthsorbi

tal

motionin24

hour

s

Distant stars

Earth orbits the Sun at anaverage speed of 66,616 mph

(107,208 km/h).

FASTFACT


WHAT ADIFFERENCE

A DAY MAKES

Are gullies on Mars from ice blocks?

It seems that the more scien-tists learn about Venus, themore questions they have.

One of the many aspects ofour sister planet shrouded inmystery is the super-rotationof its atmosphere, whichcauses winds to circle Venusin four Earth days. Andrecent analysis has shownthat these wind speeds dontstay consistent; two compli-mentary studies one by aJapanese-led team publishedin the JanuaryJournal of Geo-physical Research-Planets andone by a Russian-led teampublished in the SeptemberOctoberIcarus haverevealed that these windsvary regularly and are ulti-mately speeding up.

Using the Venus Monitor-ing Camera aboard the Euro-pean Space Agencys (ESA)Venus Express spacecraft, theteams were able to track themovements of distinct fea-tures in the clouds andtherefore determine theirvelocities. When the orbiterarrived in 2006, scientistslearned that wind speeds atlow latitudes averaged about190 mph (300 km/h). Overthe course of the mission,

the velocities increased tosome 250 mph (400 km/h).

Such a large variationhas never before beenobserved on Venus, says co-author Igor Khatuntsev ofthe Space Research Institutein Moscow, and we do notyet understand why thisoccurred.

In addition to this long-term increase, the teamsobserved localized short-term variations.

Further investigationsare needed in order toexplain what drives theatmospheric circulation pat-terns that are responsible[for the global wind speedincrease] and to explain thechanges seen in localizedareas on shorter timescales,says Hkan Svedhem, ESAs

Venus Express project scien-tist. Karri Ferron

SURFING MARS.The High Resolution Imaging Science Experiment (HiRISE) camera on NASAs Mars ReconnaissanceOrbiter spied these linear gullies on the side of a large sand dune in Russell Crater. A team of scientists suggests thesefew-meters-wide grooves result from chunks of frozen carbon dioxide, also known as dry ice, sliding down the sand.After the block stops at the base of the dune and sublimates to gas, it would leave behind the pit marks seen in theclose-up image. This research appeared in the July issue of Icarus. L. K.

Venus windsspeed up

NASA/JPLCALTECH/UNIV.

OFARIZONA

EXTRA TIME?A solar day is slightlylonger than a sidereal day because Earthis not stationary. As it orbits the Sun, ourplanet must rotate the extra amount

shown for the Sun to return to the posi-tion it held in the sky the previous day.

ASTRONOMY:MICHAELE.

BAKICHANDROENKELLY

SUPER SPEEDS.By studyingcloud features captured by theVenus Monitoring Camera on theVenus Express spacecraft, scien-tists have discovered that theplanets wind speeds haveincreased in the past six years.

ESA/MPS/D

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NASAs Chandra X-ray Observa-tory spied on our next-doorneighbor, the Andromeda Gal-axy (M31), and found 26 newblack holes. These objects,which add to nine alreadyfound, are the infinitely denseremains of dead massive stars.

Astronomers combined 150observations to find the X-rayfingerprints that uniquelyidentify these objects, a studythey published June 20 in The

Astrophysical Journal.Seven of the new objects

are within 1,000 light-years oftheir big brother the super-massive black hole at M31s

center more than scientistshave found that close to ourown black hole.

With 35 known blackholes, Andromeda has themost scientists have found inany galaxy outside the MilkyWay. Although that abun-dance is partly because M31is nearby and easier to see,this galaxy also has a largerbulge around its center thansome, like the Milk y Way,explaining why its centralneighborhood is morecrowded than ours. S. S.

Astronomers have cata-

loged some 48,000 vari-able stars those

whose brightnesses vary and these objects can

tell them a tremendousamount about the universe.

Such fluctuations can result

from a surface explosion such isthe case with a nova or changesdeep within a stars core that cause

the sun to fluctuate in size and there-fore luminosity. Researchers learn a

lot about stars, such as their rotationsand their internal compositions, by

studying stellar variability.Scientists group those stars that

vary due to intrinsic characteristicsaccording to their age, brightness, and

color (or temperature). Often, theseluminosity fluctuations correspond to

the specific stellar evolution phasethose stars are in. But astronomers

announced that they have identifieda new group of variable stars that

shouldnt exist according to stellarevolution models. They describe their

observations in the June issue ofAstronomy & Astrophysics.

The team of researchers fromGeneva Observatory in Switzerland

studied star cluster NGC 3766, whichlies some 6,500 light-years from the

Sun and is about 20 million years old.Open star clusters hold hundreds to

thousands of stars that were borntogether and therefore evolve together.

Astronomers thus study these objectsto learn about stellar evolution.

Nami Mowlavi and colleaguesobserved NGC 3766 and 26 other

open clusters several times each yearfrom 2002 through 2009 for 10 to 15

nights at a time. For all observations,they used the 1.2-meter Leonhard

Euler Telescope at La Silla, Chile.In total, they captured 3,551 images

of NGC 3766 and studied its brightest

3,547 stellar members looking for pul-sations. They then separated out five

groups of variable stars, and one ofthose is a new classification.

The team says this new, as-yet-

unnamed group has 36 members. Allof the stars are in the main sequencephase of stellar evolution, meaning

they are fusing hydrogen to producehelium and energy within their cores,

and are hot A- and B-type stars. (Suchstars are more massive than the Sun.)

They have pulsation periods between0.1 and 1.1 days, and 32 are in a nar-

rower range of 0.1 to 0.7 day. Theastronomers noted that the stars with

longer pulsation periods also havelarger brightness differences, although

all 36 stellar members brightnesses

varied by just 1 to 4 thousandths of amagnitude, or between 0.1 and 0.6percent. The pulsation periods also

remained stable over the seven yearsof observations. One-third of the new

groups members appear to pulsate inmultiple frequencies.

Mowlavi and colleagues recommendthat astronomers search other open star

clusters for more members of this newclass, which they propose be named

low amplitude periodic (or pulsating)A and late-B variables. L. K.

Chandra spies black holes

SPACE SCIENCE UPDATE

NEW TYPE OFVARIABLESTARFOUND

SPACE COLLABORATION. NASA Administrator Charles Bolden signed an agreement of cooperation with Italian SpaceAgency President Enrico Saggese to participate with the European and Japanese BepiColombo mission to Mercury.

THE RISE IN OPENACCESSUNOFFICIAL PUBLISHING

HEAVILY POPULATED.Scientists using NASAs Chandra X-rayObservatory found 26 new black holes in the Andromeda Galaxy (M31).

NOAO/AURA/NSFOPTICAL;NAS

A/CXC/SAO/BARNARD,

ETAL.

XRAYINSET

RESTLESS RESIDENTS.After analyzingseven years of observations of star clusterNGC 3766, astronomers identified a new classof variable stars that pulsate with periods of afew hours. ESO

FAST

FACT

DIGITAL DATA.Normally, to read a scientific article, you have topurchase an expensive journal subscription, unless you work at aninstitution that has one. To encourage collaboration and get scientificresults out quickly, astronomers began placing their articles on a freewebsite called the arXiv in 1992. While that year only a few peopleuploaded papers, thousands of scientists currently put their work outthere each month. The accessibility of articles has risen with the num-ber of Internet users who are hungry for scientific information.

ASTRONOMY: SARAH SCOLES ANDROEN KELLY, AFTER ARXIV AND INTERNET WORLD STATS

Nearly 2 million scientific paperswere published in 2012.



503The number of new extrasolar planet candi-

dates found by the Kepler telescope andannounced June 7 by the missions team.

More evidence for

cold dark matterBy observing 50 galaxy clusters that existedbetween 2.0 and 3.6 billion years ago, astrono-mers have found further evidence to supportthe leading theory of dark matters secret iden-tity. This material makes up some 85 percent ofthe universes mass, but it doesnt emit, absorb,or reflect radiation, so studying it is difficult.Galaxy clusters, some of the largest structuresin the universe, hold large reservoirs of darkmatter and thus make ideal cosmic laboratories

to study this mass.One way to learn more about dark matter isby utilizing a consequence of Albert Einsteinsgeneral theory of relativity: Objects with masswarp space-time. So, by studying how a mas-sive structure like a galaxy cluster bendsthe light from background objects, scientistscan learn about dark matters properties.Researchers using the Subaru Telescope atopMauna Kea in Hawaii studied this weak gravita-tional lensing resulting from 50 galaxy clustersto determine how their densities change fromtheir centers to edges.

They found that the density profiles matchthat expected if dark matter is cold, meaningthe particles move slower than light-speed andtherefore can stick together to form larger and

larger structures. Most astronomers believe theuniverses invisible matter is cold, and this newstudy, which appeared in the June 1 issue ofThe Astrophysical Journal Letters, lends supportto the theory. L. K.

FASTFACT

DARK DENSITY.Astronomers measured the slightwarping of background light due to the mass of 50 fore-ground galaxy clusters and reconstructed the dark mat-ter distribution (shown in purple) of those galaxy clustersto find that its density agrees with the leading theory.

NAOJ/ASIAA/SCHOOLOFPHYSICSANDASTRONOMY,

UNIVERSITYOFBIR

MINGHAM/KAVLIIPMU/ASTRONOMICALINSTITUTE,T

OHOKUUNIVERSITY

Scientists first discovered hints ofdark matter in the 1930s. Fritz Zwicky

noted that galaxies in the Comacluster were moving so fast that thecluster must contain invisible mass.

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16/80

Justin Bieberbuys a ticket onVirgin GalacticsSpaceShipTwo.When askedwhether he

spent $250,000to impress theladies, he was

like, Baby,baby, baby, no.

Pop starship

COSMIC WORLDA look at the best and the worst that astronomy and

space science have to offer. by Sarah ScolesCold asspace

Supernovahot

Our galacticspiral arm is

more than just aspur of a largerarm. This is theonly discoveryever to suggestEarths place in

the universeis not totallybourgeois.

Upward mobility

The Harvard-Smithsonian

Center for Astro-physics says theCats Paw Neb-ula is litteredwith new stars.This starburst isnot one whose

rainbow youwant to taste.

Mixed metaphor

Oleg Kapanetsreleases the film

Gagarin: The

First in Space. Hehas optimism tomatch the Rus-sian zeitgeist:

A separatemovie about

Gagarins deathcould be made.

Yuris night

VIRGINGALACTICPOPSTARSHIP;THINKSTOCKYURISNIGHT;S.

WIL

LISCFA,

ISU;ESA/HERSCHEL;NASA/JPLCALTECH/

SPITZER;CTIO/NOAO/AURA/NSFMIXEDMETAPHOR;NASA/JPLCALTE

CH/R.

HURTUPWARDMOBILITY

16 ASTRONOMY t OCTOBER 2013

Take a few minutes toflip through the

pages of this maga-zine. Time and time

again, youll comeacross absolutely stunning

images. Whether a HubbleSpace Telescope mosaic of the

Orion Nebula, a portrait of theAndromeda Galaxy taken from

a major observatory, or an ama-

teur astronomers photo of theHorsehead Nebula, such master-pieces inspire us to venture out

for a firsthand telescopic view.And therein lies the problem,

especially where the neophytebackyard astronomer is con-

cerned. The camera capturescolor and faint detail beyond the

grasp of the human eye alone.Unaware of that fact, newbies

peer into the eyepiece expectingan observatorys-eye view of the

Andromeda Galaxy. Instead,they see nothing more than a

grayish, oval-shaped blob. The

Orion Nebula doesnt fare much

better. The reds and greens thatare so vivid in the Hubble photo

are absent. And the Horsehead?Its nowhere to be seen!

For depictions of what theOrion Nebula, Andromeda Gal-

axy, Horsehead Nebula, andother celestial objects reallylook

like, you can do no better thanrefer to an astrosketch in its

simplest form, a pencil-and-paper rendering of what the

observer sees at the eyepiece.If youre a regularAstronomy

reader, you may be familiar withour past astrosketching features.

During a three-year run thatbegan in September 2009, Edi-

tor David J. Eicher penned themonthly piece Deep-sky Show-

case. It featured deep-sky draw-ings culled from a logbook he

kept over a 36-year span. In

January, Eicher passed on thebaton to renowned artist ErikaRix, who shares her expertise in

OBSERVINGBASICS B Y G L E N N C H A P L E

Heavenly sketchesDrawings of astronomical objects reveal what youll really

see through the eyepiece.

the column Astro

Sketching. (Youllfind this months

edition on p. 68.)In the January

2012 issue ofAstronomy, we

ran the all-encompassing

five-page articleHow to sketch

deep-sky objects,written by Brandon

Doyle. I even tackled Astro-sketching 101 in my March

2010 column. In addition, read-ers often post sketches to our

website; check out the gallery atwww.Astronomy.com/sketches.

The Internet definitely is aninvaluable source of astrosketch

galleries. One of the best is Beltof Venus (www.beltofvenus.

net), the creation of graphicartist Jeremy Perez. From there,take a cyber stroll through the

websites of Michael Vlasov(www.deepskywatch.com),

Mark Portuesi (http://www.jotabout.com/portuesi/astro),

Bill Greer (www.rangeweb.net/~sketcher), and Brandon

Doyle (http://brandon-doyle.weebly.com).

Want more? You can get aregular dose of astrosketching at

the Astronomy Sketch of theDay (ASOD) website (www.

asod.info). Besides the sketchdu jour, ASOD offers an archive

of hundreds of eyepiece draw-ings dating back to March 2007.

A common myth aboutsketching is that its an activity

for accomplished artists only.Not so! Your goal isnt to pro-

duce a museum-quality master-piece. You simply want a

pencil-and-paper rendering toplace in a logbook for future

reference. As with any facet ofart, sketching can be learned

under the proper guidance.Several online tutorials will

help. Try either of MichaelRosolinas Astro Sketching

Workshop slideshows (www.slideshare.net/mrosolina) and

Martin Lewis PowerPointpre-sentation (www.skyinspector.

co.uk). A pair of sketching how-tos by accomplished astroartist

Carol Lakomiak is available viathe Royal Astronomical Society

of Canada website (www.rasc.

ca/astrosketchers-group) oneon sketching the Moon and oneon drawing the Sun and deep-

space objects.If youre a visual learner,

these video clips will help.Check out Eichers Sketching

from the telescope (www.Astronomy.com/sketching) and

Perezs Introduction to Astro-nomical Sketching (http://

youtu.be/QDC3R39AcSA).Both offer clear step-by-step

instructions on sketching deep-sky objects.

Finally, for a complete guideto drawing at the eyepiece, I

highly recommendAstronomicalSketching: A Step-by-Step Intro-

duction(Springer, 2007). Thishandbook, part of the Patrick

Moore Practical Astronomyseries, includes sections by Rix

and Perez, as well as RichardHandy, David B. Moody, and Sol

Robbins. Its on my bookshelf; itshould be on yours.

Astrosketching is a fun alter-native to astroimaging. Its easier

than you might think, it sharp-ens your visual skills, and it ulti-

mately evolves into a portfoliothat will become a valuable life-

time resource. Give it a try!Questions, comments, or

suggestions? Email me at

[email protected]. Nextmonth: the invasion of the green

laser! Clear skies!

BROWSE THE OBSERVING BASICS ARCHIVE AT www.Astronomy.com/Chaple.

Sketches like this one of the Orion Neb-ula (M42) through an 8-inch telescopeshow observers what they can trulyexpect to see at the eyepiece. JEREMY PEREZ


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100

0

200

300

400

500

600

700

Revolutio

nspersecond

FAST

FACT

WHAT SPINS AS FAST

AS A MILLISECONDPULSAR?

When Jocelyn Bell and Anthony

Hewish discovered the first pulsarin 1967, they called it LGM-1 forlittle green man 1.


ASTRONEWSMARS CHEMICAL. The clay within martian meteorite MIL 090030contains boron, say scientists in an article published June 6 in PLOS ONE.

On June 26, two different teamsannounced surprising exoplanetfinds that could increase the num-ber of predicted planets that existin the Milky Way.

In the first study, whichappeared online inAstronomy &

Astrophysics, astronomers con-firmed that a member of a triple-star system, the low-mass sunGliese 667C, hosts at least six plan-ets, including three that orbit inthe stars habitable zone where liq-uid water could exist. This fullypacked area, the first of its kind, is

home to three super-Earths, notjust one, as previous observationsof the star system had indicated.

The discovery is importantgiven the large population of low-mass stars in the Milky Way. Thenumber of potentially habitableplanets in our galaxy is muchgreater if we can expect to findseveral of them around each low-mass star, says author Rory Barnesof the University of Washington in

Seattle. Instead of look ing at 10stars to look for a single poten-tially habitable planet, we now

know we can look at just one starand have a high chance of findingseveral of them.

Another exoplanet first ap-peared online the same day as theGliese 667C results, this time inNature, as astronomers announcedthe first transiting worlds discov-ered in an open star cluster. Thetwo planets, which are both lessthan three times the size of Earth,lie some 3,000 light-years away in

NGC 6811. Cataloged as Kepler-66b and -67b, these exoplanetswere a surprising find considering

the frequent gravity tugs andharsh stellar winds that character-ize dense star clusters.

These planets are cosmicextremophiles, says lead authorSoren Meibom of the Harvard-Smithsonian Center for Astrophys-ics in Massachusetts. Findingthem shows that small planets canform and survive for at least a bil-lion years, even in a chaotic andhostile environment. K. F.

Exoplanetsfound inunlikely

places

GOLDILOCKS GOLD MINE.After re-examining the planetary systemGliese 667C, which lies 22 light-years away in the constellation Scorpius, scien-tists confirmed that three super-Earths lie within the host stars habitable zone a region where liquid water could exist. ESO

b h? c f e d g

Habitable zone

Gliese

667C

QUICK AND DEAD.Millisecond pulsars are some of the most extreme objects in the universe. They are the rem-nants of massive stars that were compressed to the size of a city but still have the mass of our Sun, making themapproximately as dense as atomic nuclei. They can spin hundreds of times every second. In this plot, the 206 millisec-ond pulsars in the Australian Telescope National Facilitys catalog are compared to more familiar, but much smaller,objects that spin or beat at the same rates. ASTRONOMY: SARAH SCOLES AND KELLIE JAEGER


18/80

ASTRONEWS

ASTRONEWS

ASTROCONFIDENTIAL B Y K A R R I F E R R O N


Nova explosions occur when hydrogen-richmaterial on the surface of a white dwarf the

burned-out core of a Sun-like star accretedfrom a companion star experiences runaway

thermonuclear burning. Because recurrentnovae erupt every few decades, we observers

can predict their explosions (to some extent!)and therefore catch the early outburst behavior

much more reliably than in classical novae,which have only been seen to erupt once.

Recurrent novae also provide the opportunity toexamine nearly identical eruptions repeatedly.

Such observations have helped us understandwhy the ejecta from novae are rarely spherical

and the impact these explosions have on the

binary system. For example, the recurrent novaT Pyxidis erupted in April 2011 for the first timesince 1966. Our observations of the light echoes

from old debris around the pre-existing rem-nant using the Hubble Space Telescope indi-

cated that this debris is dominated by aninclined ring of material, presumably along the

systems orbitalplane, and

therefore thatthe companion

star helped shape the outflow.The distance we derived from the light

echoes also confirmed that the companion starin T Pyx loses material to the white dwarf at an

extraordinarily high rate, most likely becausethe luminous eruptions heat it and cause it to

expand. Moreover, the change in the orbitalperiod of T Pyx during the most recent outburst

showed that it ejected so much mass that itswhite dwarf is unlikely to ever become massive

enough to explode as a type Ia supernova.

Whether or not a particular accreting whitedwarf erupts as a type Ia supernova, if such highaccretion rates can be stimulated by nova erup-

tions in close binaries and if they can be main-tained for even a few decades following an

explosion, then novae must strongly impact theevolution of a close binary.

Because astronomers were not

around to see the Sun in itsyounger years, they like to findalien stars at different points intheir lives and watch how theygrow up. If they find newborn,teenage, and young-adult starssimilar to the Sun, they can fill inthe details of our stars biography.On June 5, scientists at the 222nd

meeting of the American Astro-

nomical Society in Indianapolisdescribed a fledgling solar twincalled TW Hydrae, which appears tobe in its terrible twos.

TW Hydrae currently has 80 per-cent of the Suns mass but is just 10million years old. The researchers,headquartered at the Harvard-Smithsonian Center for Astrophysics

(CfA) in Cambridge, have been

watching the star grow as it collectsgas from the protoplanetary diskthat swirls around it.

As the gas falls toward the star, ashock wave heats the gas andcauses it to emit X-rays. The gassoon cools and emits lower-energyoptical light as it heads even closerto the star.

By gathering data in multiplewavelengths, we followed the gasall the way down, says lead scien-tist Nancy Brickhouse of the CfA.We traced the whole accretionprocess for the first time.

And in watching that process,

they discovered that gas doesntpack onto the star continuouslybut in clumps. Some of the mate-rial never even makes it to the starbecause the stellar wind pushes itaway, or it falls into the magneticloops and prominences that ourcomparatively calm Sun also has.

The team will continue to inves-tigate the interplay between TWHydraes magnetic activity and itsgrowth. Understanding that con-nection will help fill in the gaps inour knowledge of how our solarsystem came to be the mature anddeveloped place it is today. S. S.

FAROUT FORMATION. A gap in the dust disk around TW Hydrae might indicate a planet is forming 80 times theEarth-Sun distance from the star, say scientists in the July 1 issue of The Astrophysical Journal.

Young star suggests our Sun was a fitful child

WHAT ARE RECURRENT NOVAE TEACHING

US ABOUT STELLAR EXPLOSIONS?

Stellar evolution

intermediaryAstronomers describe in theJune 27 issue of Naturethe dis-covery of a star in the intermedi-ate evolutionary stage betweena red giant and a white dwarf.This sun, J024725B, also pul-sates in a way not seen before,which can help scientists learnabout the stars interior.

They hope to detect similarpulsations from other stars thatmight be in the same evolution-ary phase and fill in the gaps ofstellar evolution. L. K.

STRIPPED STAR.The smallermember of the J024725 binary sys-tem is evolving from a red giant to awhite dwarf. KEELE UNIVERSITY

SPITTING IMAGE.This artists conception of TW Hydrae, a young star that willgrow up to be similar to the Sun, shows the clumpy gas that streams toward the sun.By observing this stellar system, scientists can learn more about what our own starwas like in its formative years. DAVID A. AGUILAR CFA

Scientists analysis of the T Pyxidislight echoes was based on compar-

ing them to brightness measure-ments of the white dwarf made bymembers of the American Associa-

tion of Variable Star Observers.

FASFAC

JenoSokoloskiAssociate research scientist at the Columbia

Astrophysics Laboratory in New York


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ASTRONEWS

Kepler-70b

Kepler-42b

Moon

Kepler-37b

Kepler-70c

KIC 12557548 b

Kepler-62c

Kepler-42d

Kepler-37c

Kepler-20e

Kepler-42c

Earth

Kepler-20f

Kepler-68c

Center ofgalaxy

OrionSpur Perse

usArm

Sun

Sagittariu

sArm

Center ofgalaxy

Sun

LocalArm

SagittariusArm

Perse

usA

rm


TESTING LISA. As of June 4, the optical bench of the Laser Interferometer Space Antenna (LISA) Pathfinderhas passed testing, including surviving the 35g force it will experience during its 2015 launch.

HOW MANY KNOWNEXOPLANETS SMALLER

THAN EARTH EXIST?

32kelvinsThe range of twice-a-day temperature swings

in the martian atmosphere, as detected by NASAsMars Reconnaissance Orbiter, according to a report in

the May 28 issue of Geophysical Research Letters.

Earths arm of the galaxy is muscular,astronomers announced June 3 at the222nd American Astronomical Societymeeting in Indianapolis. While theLocal Arm first appeared to be a mere

spur of the larger Sagittarius or Per-seus arms between which it is sand-wiched, new evidence shows it to bea significant limb on its own.

Scientists conception of our galaxyis still evolving because determiningthe Milky Ways shape is like mappinga building while stuck in your office.Astronomers cannot step outside andobserve the overall structure, so theyhave to get creative. To upgrade theLocal Arm to a metropolitan area, theBar and Spiral Structure Legacy (BeS-SeL) survey team monitored themotions of molecules.

BeSSeL observes natural masers,which are like lasers that emit lower-energy electromagnetic radiation in this case, water and methanol

molecules that beam photons of aspecific radio frequency into space.Astronomers then measure individualmasers velocities and parallaxes how much they appear to move rela-

tive to a distant background as Earthtravels around the Sun. The larger thechange, the closer the maser. The VeryLong Baseline Array, which madethese observations, can resolve appar-ent position changes as small as0.00017 arcsecond the size a tennisball appears from 4,800 miles (7,700kilometers) away.

Our Local Arm is a major struc-ture, says Alberto Sanna of the MaxPlanck Institute for Radio Astronomyin Bonn, Germany, maybe a branch ofthe Perseus Arm, or possibly an inde-pendent arm segment. Either way,our picture of the Milky Way is chang-ing and may continue to do so as tele-scopes become increasingly preciseand sophisticated. S. S.

The Milky Ways Local Armis metropolitan

PETITE PLANETS.Astronomers havediscovered 12 exoplanets with radii smallerthan that of Earth. These worlds wererevealed by the transit method, whichallowed scientists to determine their sizesbased on the amount of light they blockedfrom their host stars. This method, however,tells researchers nothing about their masses,so these planets densities and thereforecompositions are still a mystery.ASTRONOMY: LIZ KRUESI AND ROEN KELLY

An extrasolar planetdetected via the ra-

dial velocity methodgives away its gravity

and thus mass. Thismethod measures

how much the worldtugs on its star.

FAFA

UPWARD MOBILITY.While the old conception of the Milky Way (left) showed the Local Arm as a mere spur of a larger limb, a new picture shows it to be a significantstructure of its own. ROBERT HURT IPAC OLD; BILL SAXTON NRAO/AUI/NSF NEW

OLD NEW


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Planetary menagerie

Astronomers have discovered nearly1,000 planets orbiting other stars.Here we highlight 10 of the mostdramatic systems in the exoplanet zoo.by Richard Talcott

10

F

or decades, astronomers

scanned the skies searchingfor planets around otherstars. The searches proved

fruitless until 1991, when

Aleksander Wolszczan andDale Frail found a system of

planets circling an exoticpulsar cataloged as PSR B1257+12.Four years later, Michel Mayor and

Didier Queloz discovered a Jupiter-sized world orbiting a normal star,51 Pegasi, every 4.2 days.

Although these first two planetarysystems were totally different fromeach other, they shared one signif i-

cant characteristic: They were noth-ing like what astronomers expected

or even imagined. Basing theirideas on our solar system, scientiststhought they would find small rocky

planets close to their host star andbig gaseous planets far away. Nature,however, had other ideas. The nearly

1,000 planets now known have givenastronomers a rich mix of strange,and not so strange, worlds to explore.

Although each exoplanet isunique, some rise higher above the

crowd than others. The editors of

Astronomychose 10 as the most fasci-

nating, exciting, intriguing the

coolest, if you will known worlds.Some are individual planets, excep-

tional in their own right, while othersare systems of worlds in remarkableenvironments. The only thing certain

about the list is that it is destined tochange in the years to come asastronomers continue their hunt.

1 Alpha Centauri BbFinding a planet about the

size of Earth orbiting a star similar to

the Sun has been a holy grail of sorts

for exoplanet hunters. They achievedthis quest in 2012 when Xavier

Dumusque of the Geneva Observatoryin Switzerland and colleagues discov-ered a planet about 10 percent heavier

than our world circling a star with 93percent of the Suns mass. Even better,

the new planet resides next door, just4.36 light-years from Earth in theclosest star system to our own.

Unfortunately, Alpha Centauri Bbdoes not lie in its stars habitable zone the region where temperatures

Richard Talcottis an Astronomysenior

editor and author ofTeach Yourself Visually

Astronomy(Wiley Publishing, 2008).


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Alpha Centauri B looms on the horizon of itslone known planet, with Alpha Centauri Ashining brightly above it and our Sun a speckto its upper right. ALL PLANET ILLUSTRATIONS BY RON MILLER;FINDER CHARTS BY ASTRONOMY: ROEN KELLY


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Gliese 667C

SCORPIUS

27

ph

1

N

E

Kepler-11

CYGNUS

b

14

1922 1

N

E


world possesses a mass ofsome 169 Earths (a bitmore than half of Jupiter)

and completes an orbitevery 138 days at a dis-

tance of 0.65 AU, whichwould place it slightlyinside Venus orbit in

our solar system.

But Kepler-64b standsout because of the company

it keeps. It circles not one star,but a pair. These two orbit theircommon center of mass once every 20

days, and each one eclipses the other dur-ing every circuit. This makes Kepler-64bone of a handful of known circumbinary

planets. The larger of the stars weighs about1.5 Suns while the smaller one checks in at0.4 solar mass. But dont confuse this type

of binary host with Alpha Centauri B; inthat nearby system, the planet orbits one

of the two stars.What truly sets this system apart, how-

ever, is that it travels through space with a

second set of stars in tow. This other stellarpair lies approximately 1,000 AU (roughly30 times the distance between the Sun and

Neptune) from the planet-bearing stars.The dynamics of the quadruple star systemgives Kepler-64b a noteworthy survival

story, and a so-far unique one in the bur-geoning field of exoplanet searches.

9 Kepler-11 systemWhen it comes to stars with lots

of planets, our solar system still reignssupreme. But Earth and its seven majorsiblings likely wont be king much longer.

At least four other stars Gliese 667C,

HD 10180, HD 40307, and Kepler-11 have families with six confirmed planets,

and some of these show hints of otherpossible members.

Of these systems, the one belonging to

Kepler-11 stands out for its compact con-figuration. Its as if nature were trying tomake an entire family live in a one-room

apartment. All six planets orbit closer tothe star than Venus does to the Sun, andthe inner five would fit comfortably inside

Mercurys orbit. These arent small worlds,

either their masses range from abouttwice Earths up to slightly bigger thanNeptunes. Although this planetary system

bears little resemblance to ours, its starclosely mimics the Sun. Kepler-11 possesses

95 percent of our stars mass, and its radiusis about 10 percent larger.

10 Gliese 667C systemThe search for life in the universe

may have just gotten a bit easier. In June

2013, astronomers announced that the starGliese 667C possesses three planets withinits habitable zone, where water could exist

as a liquid on the surface. All three are so-called super-Earths that have masses largerthan our home world but smaller than 15

Earth masses, the size of Uranus. These

worlds completely fi ll the stars habitablezone no other hypothetical planet could

occupy a stable orbit within the zone.The three belong to a system that holds

at least six (and possibly seven) planets. Allorbit the star Gliese 667C, the faintestmember of a triple star system located

approximately 22 light-years from Earth.Gliese 667C has about one-third the Sunsmass and a surface temperature barely half

that of our stars. These conditions meanthe three habitable worlds lie quite close totheir parent, between 0.13 and 0.21 AU

away, so they would fit inside Mercurysorbit in our solar system.

Although the three planets in Gliese

667Cs habitable zone may not be inhab-ited, their mere existence raises the hopesof scientists seeking life beyond our solar

system. Because red dwarf stars like Gliese667C make up the majority of stars in our

galaxy, the discovery increases the chancesof finding other worlds where life couldgain a foothold.

THE EXOPL ANET ZO O CONTAINS PLEN TY OF E XOTIC W ORLD S. R EAD ABOU T FI VE THAT JUST M ISSED OUR L IST AT www.Astronomy.com/toc.

From the barren surface of Kepler-11g, its host star and five plan-etary siblings would all line up.

Coolness factor:Three planets

in habitable zone

Mass (Earths):2.76.9

Orbital radius (AU):0.050.55

Discovery year:20092013

GLIESE 667C SYSTEM Three super-Earth planetsexist in thehabitablezone whereliquid water cansurvive on thesurface of thered dwarf starGliese 667C.

Coolness factor:System with

six tightly packed planetsMass (Earths):1.925

Orbital radius (AU):0.090.47

Discovery year:2011

KEPLER11 SYSTEM
http://www.astronomy.com/http://www.astronomy.com/tochttp://www.astronomy.com/tochttp://www.astronomy.com/



Cosmology craft

The Planck spacecraft the culmination of nearly twodecades of nonstop effort by hundreds of scientistsand engineers has given astronomers their bestlook ever at the infant cosmos. Since 2009, the probehas been mapping the microwave universe and gath-

ering data on our Milky Way, galaxies across cosmic time, and thecosmic microwave background (CMB) the Big Bangs relic radia-tion. Its certainly not the first craft to study the CMB, but Planck

has produced the most detailed observations of this pervadingradiation across the cosmos.

Now, Plancks first cosmology results, announced in 29 scientificpapers in March, have confirmed astronomers leading theory ofthe universe. They have refined many cosmic parameters, such asthe universes age, how fast it is expanding, and what its composedof. But just as important as these much-publicized findings are theother results that lie within the Planck data and just how scientistsmanaged to extract that information. For embedded within the seaof microwave signals is a map of the universes matter across cosmic

time, secrets of enormousgravitationally bound superclusters ofgalaxies, and thousands of newly cataloged objects.

Astronomers have made a discovery workhorse of the EuropeanSpace Agencys (ESA) Planck mission and revealed a microwaveuniverse never before seen.

Up and awayThe Planck mission launched May 14, 2009, from Guiana SpaceCentre in Kourou, French Guiana. It collects light from a Lissa-

jous orbit around the second Sun-Earth Lagrangian point, calledL2. (This is one of five locations where the Suns and Earths gravi-tational forces equal each other, which allows Planck to maintain astable orbit with little propellant.) The L2 point sits some 930,000miles (1.5 million kilometers) from Earth in the direction oppositethe Sun. Plancks solar panel blocks the heat and light from theSun, Earth, and the Moon from blinding the spacecraft.

After weeks of cooling and calibrating the craft, astronomersbegan routine observations August 12, 2009. Planck completes oneall-sky scan in six months, collecting data through its High Fre-quency Instrument (HFI) and its Low Frequency Instrument (LFI).

Liz Kruesi, an Astronomy associate editor, writes frequently about

cosmology and the universes most extreme objects.



The helium-3 used inconjunction with helium-4 to cool

Plancks HFI to 0.1 kelvin (459.49 Fahrenheit) ran out January13, 2012; the LFI, however, will collect data through September2013. (See Plancks instruments, and how they compare to otherson p. 30.) The March 2013 release incorporates 15.5 months ofobservations, so 2.5 surveys of the sky.

Getting to the signalPlanck collects information about the CMB radiation, but it alsoobserves most energies with a frequency between 27 and 1,000gigahertz. To see only the faint CMB signal, scientists have toremove seven types of signals theyre not interested in from each ofthe instruments nine channels.

One of their tricks is actually using Plancks nine frequencybands to better define what theyre seeing. We usethe low-frequency instruments to map thegalactic rubbish and subtract it out ofthe higher-frequency maps wherewere looking for the CMB, saysBruce Partridge of Haverford

College in Pennsylvania. Dust in our galaxy and in external galax-ies is very strong at the highest frequencies. We map it at the highestfrequency and subtract it out of the intermediate frequencies.

The researchers know what the CMBs energy spectrum lookslike NASAs COsmic Background Explorer measured it in the

1990s. They then compare images through different filters of thesame location on the sky. Specifically, they look for radiation inten-sity changes that correspond to astronomical objects. Most of theforegrounds were dealing with have a different spectrum from themicrowave background, says Partridge. So by having this widefrequency range, we can characterize the foregrounds much better.

For example, high-energy particles in space called cosmicrays spiral along the Milky Ways magnetic

field. As they change directions, they emitradiation that has a strong signal in

Plancks lowest frequency bands.Because scientists have been

able to isolate these signals,

Dust in our galaxy, cold prestellar objects, and the cosmic microwave back-ground glow in long-wavelength microwave radiation. The Planck spacecrafthas mapped this emission with better resolution than any previous all-skymicrowave probe. ESA/LFI & HFI CONSORTIA

0.1 kelvinThe temperature Plancks High Frequency

Instrument must be cooled to

This new spacecraft has mapped the universesmatter, refined its composition and age, andrevealed thousands of radio sources.

by Liz Kruesi
http://www.astronomy.com/http://www.astronomy.com/


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Reflector

Passive coolingsystem

Low FrequencyInstrument

High FrequencyInstrument

Helium-3 andhelium-4 tanks

for cooling

Telescope baffle

0 10 20 30 40 50 60 70 80

4.6

4.9

26.8

23.6

71.8

68.3

Percentage of total

Wilkinson MicrowaveAnisotropy Probe

Planck

Ordinarymatter

Darkmatter

Darkenergy


theyve also compiled catalogs of those foreground sources. Onesuch release contains 24,119 compact sources (any spot on the skythat emits microwave radiation). Planck has given astronomers aradio playground to investigate.

Universe originsPlancks main purpose, of course, is to precisely map the CMB.The past century of observational evidence and especially otherCMB measurements has strengthened the Big Bang theory,which says the universe began some 13.8 billion years ago as a sear-ing, densely compressed area of radiation and subatomic particles.Immediately afterward, our tiny universe expanded tremendously(1030) in just 1036second; scientists call that fraction of time the

inf lationary era. (Still an unobserved cosmic epoch, inflation isbacked by mounds of evidence.)

After this period, the universe continued to expand (at a lowerrate) and thus cool. A few minutes after the Big Bang, quarks com-

bined to form protons and neutrons. Those particles sloshedaround with electrons and radiation bits, called photons. Forthousands of years, radiation collided with other particles.

Then, when the universe had expanded enough to cool to 3000 K(4940 F), electrons and protons could combine as neutral hydrogenatoms, so photons had fewer particles to bounce off. The radiationcould stream free. This time of last scattering, as scientists call it,occurred about 370,000 years after the Big Bang. The light has beentraveling since then, filling the universe and landing on astronomersdetectors as blips of energy. Cosmic expansion has stretched, or red-shifted, that radiations wavelengths from infrared to microwave.

This radiation carried with it a picture of what the cosmoslooked like at the time of last scattering. Regions packed with

slightly more mass were warmer. On the resultant Planck CMBtemperature map, the redder (warmer) regions eventually pulled inmore matter and formed into todays superclusters of galaxies. Butthats not the only bit of information this map reveals.

Cosmic characteristicsPlanck scientists use the data compiled from the satellites ninewavelength bands to determine an array of cosmic parameters such as the universes age and the amounts of normal, or baryonic,matter that stars and people are made of; dark matter, a mysteriousinvisible mass; and dark energy, what seems to be speeding up cos-mic expansion. The CMB map may look clumpy with different-sized spots across the sky, but astronomers break apart this signal

e cosmic recipe

Using the new data from Planck, astronomers have revised the percent-ages of ordinary matter, dark matter, and dark energy that make up theuniverse. ASTRONOMY: ROEN KELLY

A look inside the Planck spacecraft shows how much of the volumeis dominated by cooling systems to ensure that the High and LowFrequency Instruments can detect temperature and thus energy differences a million times smaller than a degree. ESA/AOES MEDIALAB

PLANCKS INSTRUMENTS, AND HOW THEY COMPARE TO OTHERSPlanck is the third-generation cos-

mic microwave background (CMB)

spacecraft. The first one, the COs-

mic Background Explorer (COBE),

measured the radiations tempera-

ture profile in the 1990s accurately

to 2.725 0.002 kelvin (454.8

Fahrenheit), matching the valuethat scientists best theory

hypothesizes. The Wilkinson

Microwave Anisotropy Probe

(WMAP), the second-generation

CMB detector, then measured the

CMBs temperature variations as it

operated from 2001 through 2010.

WMAP and Planck work differ-

ently from COBE. Each measured

how specific spots in the sky differ

in temperature. But Planck views

the sky across a wider range of the

electromagnetic spectrum and can

see finer details. WMAPs detectors

had a sensitivity of 20 millionthsof a kelvin and could resolve

angles as small as 15 arcminutes

( degree); Plancks detectors have

a sensitivity of two millionths of a

kelvin and can resolve angles as

small as 5 arcminutes ( degree).

It also can see wavelengths 10

times shorter than WMAP could.

Plancks High Frequency Instru-

ment (HFI) collects light in six fre-

quency bands centered on 100

gigahertz, 143 GHz, 217 GHz, 353

GHz, 545 GHz, and 857 GHz. Each

collection band has a width, andthus HFI covers most frequencies

between 84 and 1,000 GHz. This

range spans radiation with wave-

lengths from 3.6 millimeters to

0.3mm. (Visible light corresponds

to energy with wavelengths

between 390nm and 700nm, or

roughly 1,000 times shorter.)

The Low Frequency Instrument

(LFI) measures light across three

bands between 27 and 77 GHz,

which spans 11.1mm to 3.9mm.

HFIs detectors must be kept

extraordinarily cold to register a

radiation change. A four-stepcooling system aboard Planck

brings the instruments tempera-

ture to just 0.1 K, making it the

coldest place in space. LFIs detec-

tors can operate at a higher tem-

perature about 20 K. L. K.


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18900

1

2

3

4

5

6

1 0.2 0.1 0.07Angular scale

Temperaturefluctuations

(thousandthsofakelvin)2


into its constituents. They essentially bin all the sizes a certainnumber are 2 wide, 1 wide, wide, and so on. They then plothow the temperature varies as a function of the sizes on the sky.This comparison is called the angular power spectrum, and eachbump on the plot corresponds to a binned variation size in theCMB map (see Listen to the universe, above).

Planck scientists model a universe with six specific variations for example, the density of baryonic matter and the fraction ofphotons that run into electrons and compare that to the angular

power spectrum compiled from the da

astronomy magazine october 2013

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