Oldest Object in Universe Found : Discovery News
The universe's most senior citizen is a galaxy that formed 600 million years after the Big Bang.
The earliest known astronomical object is a galaxy appearing about 600 million years after the universe formed.
The previously known most distant object was a short-lived gamma ray burst.
The newly discovered galaxy is interesting to astrophysicists trying to understand how these early objects changed gas in interstellar space.
Homing in on an object found during the Hubble Space Telescope's long, deep stare into the distant past, astronomers have fished out a galaxy whose light has traveled more than 13 billion light-years to get here, making it the oldest astronomical object found so far.
The universe's most senior citizen is called UDFy-38135539, but scientists suspect its title as record-holder -- previously held by a gamma-ray burst -- will not last.
"I don't think this is the limit, perhaps not even that close to it," lead researcher Matthew Lehnert, with France's Observatoire de Paris, told Discovery News.
Measurements taken of UDFy-38135539 by Lehnert and colleagues confirm it formed within 600 million years of the universe's creation. Theoretical models and computer simulations suggest that the first galaxies could have formed as early as 200 million years after the Big Bang event.
Lehnert says it will be increasingly more difficult to find these objects, since they would be extremely faint and have much fewer stars and gas to make their presence known.
"UDFy-38135539 was already a challenge and perhaps we won't be able to do much better than it for a while yet," Lehnert said, adding that it took about four years of work to make the jump from the 2006 detection of the previously known most distant galaxy, which existed about 750 million years after the Big Bang (a distance referred to in scientific parlance as a redshift of 6.96) to confirmation of UDFy-38135539 at a redshift of 8.6.
Redshift refers to what happens when light seen coming from an object is proportionally shifted to appear more red. It is similar to how the sound of a train's whistle seems to shift as it recedes into the distance. The universe as it appears today is redshift 0. Redshift 1 refers to when the universe was half its present age.
"Redshift 8.6 is likely to be about as high as we can reach with the current generation of telescopes," astrophysicist Michele Trenti, with the University of Colorado in Boulder, told Discovery News. "With the Hubble Space Telescope it might be possible to find some galaxies up to redshift 10, but these objects are expected to be very rare and extremely faint."
Confirmation of a galaxy within 600 million light-years of the Big Bang is particularly interesting to scientists because it is during this time that radiation from the first objects in the universe is believed to have stripped off electrons from hydrogen atoms created during the Big Bang, added Trenti,.
"It's quite amazing to me that humble, small galaxies -- the ones that likely existed at this high redshifts, early in the history of the universe -- could literally change its overall state," Lehnert said.
What is clear is that UDFy-38135539 couldn't have ionized the gas on its own.
"It raises the question what are these other sources and are they like UDFy-38135539 or not? We know from the (Hubble Ultra Deep Field) images that whatever they are, they are not detected in those images. We need more data and much deeper data," Lehnert said.
The research appears in this week's issue of Nature.