"Long before it's in the papers"
September 20, 2012

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Record-distance galaxy may confirm theories

Sept. 20, 2012
Courtesy of the Carnegie Institution
and World Science staff

A gal­axy has been de­tected at pos­sibly a rec­ord dis­tance from us, and its size is con­sist­ent with main­stream the­o­ries that hold the ear­li­est ga­lax­ies were small, as­tro­no­mers say.

Lead­ing cos­mo­lo­g­i­cal the­o­ries main­tain that rel­a­tively ti­ny early ga­lax­ies merged pro­gres­sively to be­come the larg­er ones we see to­day. By ob­serv­ing a very dis­tant gal­axy, as oc­curred in this case, sci­en­tists say they’re al­so see­ing a gal­axy that ex­isted far back in time, since its light takes a long time to get he­re.

Com­pos­ite col­or im­age of clus­ter MAC­S1149+2223. Its huge grav­i­ta­tion­al force makes a "cos­mic lens" that mag­ni­fies an ex­treme­ly dis­tant gal­axy in the back­ground, as shown in the in­let." (Cred­it: The CLASH team / The Space Tel­e­scope Sci­ence In­sti­tute)

With the com­bined pow­er of NA­SA’s Spit­zer and Hub­ble Space Tele­scopes, as well as a cos­mic mag­nif­ica­t­ion ef­fect, a team of as­tro­no­mers, in­clud­ing Dan­iel Kel­son of the Car­ne­gie In­sti­tu­tion for Sci­ence in Wash­ing­ton, spot­ted what they said could be the most dis­tant gal­axy ev­er seen. Light from the young gal­axy cap­tured by the or­bit­ing ob­ser­va­to­ry was emit­ted when our 13.7-bil­lion-year-old uni­verse was just 500 mil­lion years old. Their work is pub­lished in the Sept. 20 is­sue of the re­search jour­nal Na­ture.

The far-off gal­axy ex­isted during an im­por­tant era when the uni­verse just emerged from the so-called cos­mic Dark Ages, as­tro­no­mers say. Dur­ing this pe­ri­od, the uni­verse went from a dark, star­less ex­panse to a rec­og­niz­a­ble cos­mos full of ga­lax­ies. The discovery of the faint, small gal­axy the­refore is be­lieved to open a win­dow in­to the deep­est, re­mot­est ep­ochs of cos­mic his­to­ry.

“This gal­axy is the most dis­tant ob­ject we have ev­er ob­served with high con­fi­dence,” said Wei Zheng of Johns Hop­kins Uni­vers­ity in Mar­y­land, the lead au­thor of the stu­dy. “Fu­ture work in­volv­ing this gal­ax­y—as well as oth­ers like it that we hope to find­—will al­low us to study the uni­verse’s ear­li­est ob­jects and how the Dark Ages end­ed.”

Light from the pri­mor­di­al gal­axy trav­eled an es­ti­mat­ed 13.2 bil­lion light-years be­fore reach­ing NASA’s tele­scopes. In oth­er words, the star­light snagged by Hub­ble and Spitzer would have left the gal­axy when the uni­verse was just 3.6 per­cent of its pre­s­ent age.

Un­like pre­vi­ous de­tec­tions of this ep­och’s gal­axy can­di­dates, which were only glimpsed in a sin­gle col­or, or wave­band, this new­found gal­axy has been seen in five wave­bands, the re­search­ers said. As part of the Clus­ter Lens­ing And Su­per­no­va sur­vey with Hub­ble (CLASH) pro­gram, the Hub­ble Space Tel­e­scope reg­is­tered the newly de­scribed, far-flung gal­axy in four vis­i­ble and in­fra­red wave­bands, and Spitzer meas­ured it in a fifth in­fra­red band.

Ob­jects at these ex­treme dis­tances are mostly be­yond the de­tec­tion sen­si­ti­vity of to­day’s larg­est tele­scopes. To catch sight of these ear­ly, dis­tant ga­lax­ies, as­tro­no­mers rely on “gravita­t­ional lens­ing.” In this phe­nom­e­non, pre­dicted by Al­bert Ein­stein a cen­tu­ry ago, the gra­vity of fore­ground ob­jects warps and mag­ni­fies the light from back­ground ob­jects. A mas­sive gal­axy clus­ter sit­u­at­ed be­tween our gal­axy and the new­found, early gal­axy mag­ni­fied the lat­ter’s light, bright­en­ing the re­mote ob­ject some 15 times and bring­ing it in­to view.

Based on the Hub­ble and Spitzer ob­serva­t­ions, as­tro­no­mers think the dis­tant gal­axy is less than 200 mil­lion years old. It is al­so small and com­pact, con­tain­ing only about one per­cent of the Milky Way’s mass. Ac­cord­ing to lead­ing cos­mo­lo­g­i­cal the­o­ries, the first ga­lax­ies should in­deed have started out ti­ny. They then pro­gres­sively merged, even­tu­ally ac­cu­mu­lating in­to the siz­a­ble ga­lax­ies of the more mod­ern uni­verse.

“These first ga­lax­ies likely played the dom­i­nant role in the ep­och of reion­iz­a­tion, the event that sig­naled the end of the uni­verse’s Dark Ages,” Kel­son said. “In es­sence, the light was fi­nally able to pen­e­trate the fog of the uni­verse.”

Hy­dro­gen gas is thought to have formed from cool­ing par­t­i­cles, about 400,000 years af­ter the birth of the uni­verse. The first lu­mi­nous stars and their host ga­lax­ies, howev­er, did not emerge un­til a few hun­dred mil­lion years lat­er. The en­er­gy re­leased by the ear­li­est ga­lax­ies is thought to have caused the elec­tric­ally neu­tral hy­dro­gen strewn through­out the uni­verse to ion­ize, or lose an elec­tron, a state that the gas has re­mained in since that time.

As­tro­no­mers plan to study the rise of the first stars and ga­lax­ies and the ep­och of reion­iz­a­tion with the suc­ces­sor to both the Hub­ble and Spitzer tele­scopes, NASA’s James Webb Tel­e­scope, slat­ed for launch in 2018. The newly de­scribed, dis­tant gal­axy will likely be a prime tar­get giv­en the good for­tune of it be­ing so strongly gravita­t­ionally lensed, sci­en­tists say.

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A galaxy has been detected at possibly a record distance from us, and its size is consistent with mainstream theories that hold the earliest galaxies were small, astronomers say. Leading cosmological theories maintain that relatively tiny early galaxies merged progressively to become the larger ones we see today. By observing a very distant galaxy, as occurred in this case, scientists say they’re also seeing a galaxy that existed far back in time, since its light takes a long time to get here. With the combined power of NASA’s Spitzer and Hubble Space Telescopes, as well as a cosmic magnification effect, a team of astronomers, including Daniel Kelson of the Carnegie Institution for Science in Washington, spotted what they said could be the most distant galaxy ever seen. Light from the young galaxy captured by the orbiting observatories was emitted when our 13.7-billion-year-old universe was just 500 million years old. Their work is published in the Sept. 20 issue of the research journal Nature. The far-off galaxy existed within an important era when the universe just emerged from the so-called cosmic Dark Ages, astronomers say. During this period, the universe went from a dark, starless expanse to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy therefore is believed to open a window into the deepest, remotest epochs of cosmic history. “This galaxy is the most distant object we have ever observed with high confidence,” said Wei Zheng of Johns Hopkins University in Maryland, the lead author of the study. “Future work involving this galaxy—as well as others like it that we hope to find—will allow us to study the universe’s earliest objects and how the Dark Ages ended.” Light from the primordial galaxy traveled an estimated 13.2 billion light-years before reaching NASA’s telescopes. In other words, the starlight snagged by Hubble and Spitzer would have left the galaxy when the universe was just 3.6 percent of its present age. Unlike previous detections of this epoch’s galaxy candidates, which were only glimpsed in a single color, or waveband, this newfound galaxy has been seen in five wavebands, the researchers said. As part of the Cluster Lensing And Supernova survey with Hubble (CLASH) program, the Hubble Space Telescope registered the newly described, far-flung galaxy in four visible and infrared wavelength bands, and Spitzer measured it in a fifth longer-wavelength infrared band, placing the discovery on firmer ground. Objects at these extreme distances are mostly beyond the detection sensitivity of today’s largest telescopes. To catch sight of these early, distant galaxies, astronomers rely on “gravitational lensing.” In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. A massive galaxy cluster situated between our galaxy and the newfound, early galaxy magnified the latter’s light, brightening the remote object some 15 times and bringing it into view. Based on the Hubble and Spitzer observations, astronomers think the distant galaxy is less than 200 million years old. It is also small and compact, containing only about one percent of the Milky Way’s mass. According to leading cosmological theories, the first galaxies should indeed have started out tiny. They then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe. “These first galaxies likely played the dominant role in the epoch of reionization, the event that signaled the end of the universe’s Dark Ages,” Kelson said. “In essence, the light was finally able to penetrate the fog of the universe.” About 400,000 years after the Big Bang, neutral hydrogen gas formed from cooling particles. The first luminous stars and their host galaxies, however, did not emerge until a few hundred million years later. The energy released by the earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the universe to ionize, or lose an electron, a state that the gas has remained in since that time. Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionization with the successor to both the Hubble and Spitzer telescopes, NASA’s James Webb Telescope, slated for launch in 2018. The newly described, distant galaxy will likely be a prime target given the good fortune of it being so strongly gravitationally lensed, scientists say.