NASA Telescopes Help Find Rare Galaxy at Dawn of Time

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Feature: 2011-392 Dec. 21, 2011

NASA Telescopes Help Find Rare Galaxy at Dawn of Time

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-392&cid=release_2011-392

Astronomers using NASA's Spitzer and Hubble space telescopes have discovered that one of the
most distant galaxies known is churning out stars at a shockingly high rate. The blob-shaped galaxy,
called GN-108036, is the brightest galaxy found to date at such great distances.

The galaxy, which was discovered and confirmed using ground-based telescopes, is 12.9 billion
light-years away. Data from Spitzer and Hubble were used to measure the galaxy's high star
production rate, equivalent to about 100 suns per year. For reference, our Milky Way galaxy is about
five times larger and 100 times more massive than GN-108036, but makes roughly 30 times fewer
stars per year.

"The discovery is surprising because previous surveys had not found galaxies this bright so early in
the history of the universe," said Mark Dickinson of the National Optical Astronomy Observatory in
Tucson, Ariz. "Perhaps those surveys were just too small to find galaxies like GN-108036. It may
be a special, rare object that we just happened to catch during an extreme burst of star formation."

The international team of astronomers, led by Masami Ouchi of the University of Tokyo, Japan, first
identified the remote galaxy after scanning a large patch of sky with the Subaru Telescope atop
Mauna Kea in Hawaii. Its great distance was then carefully confirmed with the W.M. Keck
Observatory, also on Mauna Kea.

"We checked our results on three different occasions over two years, and each time confirmed the
previous measurement," said Yoshiaki Ono of the University of Tokyo, lead author of a new paper
reporting the findings in the Astrophysical Journal.

GN-108036 lies near the very beginning of time itself, a mere 750 million years after our universe
was created 13.7 billion years ago in an explosive "Big Bang." Its light has taken 12.9 billion years
to reach us, so we are seeing it as it existed in the very distant past.

Astronomers refer to the object's distance by a number called its "redshift," which relates to how
much its light has stretched to longer, redder wavelengths due to the expansion of the universe.
Objects with larger redshifts are farther away and are seen further back in time. GN-108036 has a
redshift of 7.2. Only a handful of galaxies have confirmed redshifts greater than 7, and only two of
these have been reported to be more distant than GN-108036.

Infrared observations from Spitzer and Hubble were crucial for measuring the galaxy's star-
formation activity. Astronomers were surprised to see such a large burst of star formation because
the galaxy is so small and from such an early cosmic era. Back when galaxies were first forming, in
the first few hundreds of millions of years after the Big Bang, they were much smaller than they are
today, having yet to bulk up in mass.

During this epoch, as the universe expanded and cooled after its explosive start, hydrogen atoms
permeating the cosmos formed a thick fog that was opaque to ultraviolet light. This period, before
the first stars and galaxies had formed and illuminated the universe, is referred to as the "dark
ages." The era came to an end when light from the earliest galaxies burned through, or "ionized," the
opaque gas, causing it to become transparent. Galaxies similar to GN-108036 may have played an
important role in this event.

"The high rate of star formation found for GN-108036 implies that it was rapidly building up its
mass some 750 million years after the Big Bang, when the universe was only about five percent of
its present age," said Bahram Mobasher, a team member from the University of California,
Riverside. "This was therefore a likely ancestor of massive and evolved galaxies seen today."

Other authors include: Kyle Penner and Benjamin J. Weiner of the University of Arizona, Tucson;
Kazuhiro Shimasaku and Kimihiko Nakajima of the University of Tokyo; Jeyhan S. Kartaltepe of
the National Optical Astronomy Observatory; Hooshang Nayyeri of the University of California,
Riverside; Daniel Stern of NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Nobunari
Kashikawa of the National Astronomical Observatory of Japan; and Hyron Spinrad of University of
California, Berkeley.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science Center at the California
Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about
Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

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