Anancient galaxy has broken therecord for the most distant point in the sky known to date, with itslighttaking roughly 13.1 billion years to reach Earth.
Thisgalaxy may provide insightinto what the first stars were like and how they influenced theformation ofthe universe, researchers said. [Photo of the most distantgalaxy]
Thenew record-holder is namedUDFy-38135539 and contains roughly a billion stars that would haveformedwithin 600 million years of the Big Bang, which scientists thinkstarted theuniverse 13.7 billion years ago.
Thedistant galaxy was discoveredby the HubbleSpace Telescope in 2009. In the new study, researchers usedthe Very LargeTelescope in Chile to observe the galaxy for 16 hours to confirm itsdistancefrom Earth by measuring how much its extremely faint glow was distortedby theexpansion of the universe. UDFy-38135539 was found to be about 100millionlight-years farther than the previous record-holder, a gamma-ray burst.
Clearing out the fog
Scientistsare intrigued byUDFy-38135539 because it is the first galaxy known to havelived fullywithin the so-called epoch of reionization, which they say lasted fromabout150 million to 800 million years afterthe Big Bang.
Back then, intense ultravioletradiation from the firststars was clearing the opaque fog that filled the cosmos by splittingitshydrogen atoms into electrons and protons, a process known asreionization.
"One of the most dramatic impactsgalaxies have had onthe whole historyof the universe is through reionization," said MatthewLehnert at theParis Observatory in France. Lehnert is lead author of theUDFy-38135539 studyappearing in tomorrow's issue(Oct. 21) of the journal Nature.
"This is the first time we know forsure that we arelooking at one of the galaxies that cleared out the fog which hadfilled thevery early universe," said one of study's co-authors, Nicole Nesvadbaatthe University of Paris-Sud in France.
Window into the past
UDFy-38135539 may yield key cluesinto this mysterious timein the universe's history.
For instance, the researchers deducedthat a bubble ofionized hydrogen gas at least 6.5 million light-years wide surroundedUDFy-38135539.
Since this bubble seemed larger thanwhat the galaxy couldhave carved out by its own light, "there must be other galaxies —probablyfainter and less-massive nearby companions of UDFy-38135539 — which alsohelped make the space around the galaxy transparent," said co-authorMarkSwinbank at Durham University in England. "Without this additionalhelp,the light from the galaxy, no matter how brilliant, would have beentrapped inthe surrounding hydrogen fog, and we would not have been able to detectit."
Such tiny galaxies could have beenthe primary sources ofionization during this epoch, the researchers suggested.
Still, it is possible that it was aflattened bubble thatappears large only along our line of sight, they acknowledged.Astronomerswould need to examine more galaxies from this time to be sure.
"This is just the type of sciencethat will be routinewhen ESO's European Extremely Large Telescope — which will be thebiggestoptical and near infrared telescope in the world — becomesoperational,"
said co-author Jean-Gabriel Cuby ofthe Laboratory ofAstrophysics of Marseille in France.
Previous cosmic distancerecords
Thegalaxy UDFy-38135539joins an elite group of far-flung cosmic objects in the distant regionsof theuniverse.
Untilnow, the object known to bethe mostdistant in the universe was the gamma-ray burst discoveredjust last year,whose light took about 13 billion years to reach here. The most remotegalaxywas IOK-1, whose light took 12.88 billion years to reach Earth.
Althoughthe difference in age of100 million years or so between that gamma-ray burst and UDFy-38135539mightnot seem like much, "in that time, the universe changes ratherdramatically — reionization happened over just a few hundred millionyears," Lehnert told SPACE.com.
- Photos:Amazing Galaxy Images
- Top10 Star Mysteries
- MostMassive Galaxy Cluster of Early Universe Discovered