Hubble spots presumed oldest galaxy: Hot, faint, and 13 billion years old
Wednesday, January 26, 2011; 1:13 PM
Hubble's still got it.
The aging beauty of a space telescope has glimpsed a presumed galaxy that astronomers say might just be the oldest thing ever seen, a small, hot affair that blazed to life during the childhood of the cosmos.
Age of Hubble: Almost 21.
Age of the possible galaxy: 13 billion years, give or take.
Although NASA's Hubble has offered a generation's worth of spectacular images - sparkling galaxies, billowing nebulae, stunning star clusters - its latest quarry lacks charisma. The presumed oldest galaxy is but a faint smudge on Hubble's Ultra Deep Field image, the astronomical equivalent of a days-long staring contest.
In 2009, Hubble's operators turned the telescope toward a dark pocket in the southern sky and "bored a hole," in the words of one Hubble enthusiast, funneling a trickle of light thrown off by the most ancient stuff we've ever seen.
The Ultra Deep Field displays a roiling zoo of galaxies - thin ones, fat ones, cigars, pinwheels, discs, and clouds. But the oldest galaxy is nothing but a smear.
Still, this "candidate" galaxy - so-called because it could turn out to be something much less exciting - marks the latest entry in a quickening deep-space race among astronomers to bag and tag ever older objects.
Hubble's new wide field camera 3, installed during a tense 2009 spacewalk, has sparked the race, peering into the heavens with 40 times the sensitivity of its predecessor.
"The idea that you can detect something from the beginning of cosmic time by looking at a patch of sky for 87 hours is just wild," says Rychard Bouwens, an astronomer from Leiden Observatory in the Netherlands, who led the team that made the discovery.
As for the impossible-sounding age of the possible galaxy, Bouwens adds, "I'm kind of wowed by it myself."
Or, as Daniel Fabricant, an astronomer at Harvard University puts it: "If true, the discovery would be a very big deal."
Writing in the journal Nature, Bouwens and his team say they are 80 percent certain the object is, in fact, an ancient galaxy. They won't know for sure until new telescopes come online over the next few years, particularly the over-budget James Webb Space Telescope, slated to replace Hubble in 2015.
Light from the presumed galaxy lies outside the range of human vision, smeared deep into the infrared by the extreme velocity at which the object is racing away from us - some 98 percent the speed of the light, the universe's ultimate speed limit.
Measuring this redshift tells astronomers the age - and distance - of stars, galaxies, and other heavenly objects.
But because Hubble's new camera lacks the capability to directly measure redshift, Bouwens and his colleagues instead employed a proxy measure made possible by a cloudy quirk of the primordial universe.
As the first stars sparked to life, great clouds of hydrogen and helium filled the universe. This fog absorbed much of the visible light produced by early galaxies, cosmologists say, providing a signature drop-out of light waves at particular frequencies. Bouwens detected such drop-outs for the presumed galaxy.
This technique dates the galaxy to the childhood of the cosmos, just 500 million years after the Big Bang, the cataclysmic explosion that rocketed the universe into existence. No other data exist from this early epoch, leaving cosmologists eager to fill the gaps in their knowledge.
Observations from the new camera, and from another NASA space telescope called Spitzer, tell us that the first galaxies were small-less than one percent the mass of our own Milky Way-and hot, blazing with early stars that hungrily gobbled up the hydrogen fuel around them. "They were forming stars as fast as they could," Bouwens says.
And although the new galaxy might be one of the first, an explosion in galactic growth soon followed. By 2 billion years after the Big Bang, the universe had grown out of its childhood, and galaxy formation slowed dramatically.
"If you would have asked me five years ago if we could see things this old and study them in any detail, I'd say, 'No, they're too faint,' " says Matt Lehnert, an astrophysicist at the Paris Observatory who last October spotted a galaxy almost as old as the new candidate.
So the race to peer deeper and deeper into space continues. Lehnert's galaxy - which is a more certain find than the new candidate - hails from about 600 million years after the Big Bang. In April 2009, a group led by Edo Berger of Harvard University reported signals from a massive star that went supernova some 30 million years after that.
"We have a friendly competition with the galaxy people over who has the most distant object," says Berger, who hunts for distant supernovae with NASA's orbiting Swift observatory. "We've been leapfrogging each other recently."
Now Berger is poised to leap ahead again. As soon as next week, he says, he will announce another ancient supernova that could push back the distance record even further, and once again we'll have a newest oldest thing in the universe.