NASA Telescopes Spy Ultra-Distant Galaxy

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Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@nasa.gov

News release: 2012-294 Sept. 19, 2012

NASA Telescopes Spy Ultra-Distant Galaxy

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-294&cid=release_2012-294

PASADENA, Calif. -- With the combined power of NASA's Spitzer and Hubble space
telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the
most distant galaxy ever seen. Light from the young galaxy captured by the orbiting
observatories first shone when our 13.7-billion-year-old universe was just 500 million years old.

The far-off galaxy existed within an important era when the universe began to transit from the
so-called cosmic dark ages. 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 opens a window
onto the deepest, most remote epochs of cosmic history.

"This galaxy is the most distant object we have ever observed with high confidence," said Wei
Zheng, a principal research scientist in the department of physics and astronomy at Johns
Hopkins University in Baltimore who is lead author of a new paper appearing in Nature. "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 approximately 13.2 billion light-years before reaching
NASA's telescopes. In other words, the starlight snagged by Hubble and Spitzer left the galaxy
when the universe was just 3.6 percent of its present age. Technically speaking, the galaxy has a
redshift, or "z," of 9.6. The term redshift refers to how much an object's light has shifted into
longer wavelengths as a result of the expansion of the universe. Astronomers use redshift to
describe cosmic distances.

Unlike previous detections of galaxy candidates in this age range, which were only glimpsed in a
single color, or waveband, this newfound galaxy has been seen in five different wavebands. As
part of the Cluster Lensing And Supernova Survey with Hubble Program, the Hubble Space
Telescope registered the newly described, far-flung galaxy in four visible and infrared
wavelength bands. 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 galaxy magnified the newfound galaxy'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 was less than
200 million years old when it was viewed. It also is small and compact, containing only about 1
percent of the Milky Way's mass. According to leading cosmological theories, the first galaxies
indeed should 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 demise of the universe's dark ages. This epoch began about 400,000 years after the
Big Bang when neutral hydrogen gas formed from cooling particles. The first luminous stars and
their host galaxies emerged a few hundred million years later. The energy released by these
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.

"In essence, during the epoch of reionization, the lights came on in the universe," said paper co-
author Leonidas Moustakas, a research scientist at NASA's Jet Propulsion Laboratory, a division
of the California Institute of Technology in Pasadena, Calif.

Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionization
with the successor to both Hubble and Spitzer, NASA's James Webb Telescope, which is
scheduled for launch in 2018. The newly described distant galaxy will likely be a prime target.

For more information about Spitzer, visit http://www.nasa.gov/spitzer . For more information
about Hubble, visit: http://www.nasa.gov/hubble .

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