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| A galaxy cluster 7.7 billion light-years away has been discovered using infrared data from NASA's Wide-field Infrared Survey Explorer (WISE). Image credit: NASA/JPL-Caltech/UCLA/WIYN/Subaru |
Our
solar system, with its colorful collection of planets, asteroids and comets, is
a fleck in the grander cosmos. Hundreds of billions of solar systems are
thought to reside in our Milky Way galaxy, which is itself just a drop in a sea
of galaxies.
The
rarest and largest of galaxy groupings, called galaxy clusters, can be the
hardest to find. That's where NASA's Wide-field Infrared Survey Explorer (WISE)
can help. The mission's all-sky infrared maps have revealed one distant galaxy
cluster and are expected to uncover thousands more.
These
massive structures are collections of up to thousands of galaxies bound
together by gravity. They were born out of seeds of matter formed in the very
early universe, and grew rapidly by a process called inflation.
"One
of the key questions in cosmology is how did the first bumps and wiggles in the
distribution of matter in our universe rapidly evolve into the massive
structures of galaxies we see today," said Anthony Gonzalez of University
of Florida, Gainesville, who led the research program. The results are
published in the Astrophysical Journal.
"By
uncovering the most massive of galaxy clusters billions of light-years away
with WISE, we can test theories of the universe's early inflation period."
WISE
completed its all-sky survey in 2011, after surveying the entire sky twice at
infrared wavelengths. The 16-inch (40-centimeter) telescope ran out of its
coolant as expected in 2010, but went on to complete the second sky scan using
two of its four infrared channels, which still functioned without coolant. At
that time, the goal of the mission extension was to hunt for more near-Earth
asteroids via a project called NEOWISE.
NASA
has since funded the WISE team to combine all that data, allowing astronomers
to study everything from nearby stars to distant galaxies. These
next-generation all-sky images, part of a new project called
"AllWISE," will be significantly more sensitive than those previously
released, and will be publicly available in late 2013.
Gonzalez
and his team plan to use the enhanced WISE data to hunt for more massive galaxy
clusters. The first one they spotted, MOO J2342.0+1301, is located more than 7
billion light-years away, or halfway back to the time of the Big Bang. It is
hundreds of times more massive than our Milky Way.
By
scanning the whole sky with the improved AllWISE data, the team will sleuth out
the true monsters of the bunch, clusters as big as thousands of times the mass
of the Milky Way, assembled even earlier in the history of the universe.
Galaxy
clusters from the first half of the universe are hard to find because they are
so far away and because not very many had time to assemble by then. What's
more, they are especially hard to see using visible-light telescopes: light
that left these faraway structures in visible wavelengths has been stretched
into longer, infrared wavelengths due to the expansion of space. WISE can hunt
some of these rare colossal structures down because it scanned the whole sky in
infrared light.
"I
had pretty much written off using WISE to find distant galaxy clusters because
we had to reduce the telescope diameter to only 16 inches [40 centimeters] to
stay within our cost guidelines, so I am thrilled that we can find them after
all," said Peter Eisenhardt, the WISE project scientist at NASA's Jet
Propulsion Laboratory, Pasadena, Calif. and an author of the new paper.
"The longer exposures from AllWISE open the door wide to see the most
massive structures forming in the distant universe."
Other
projects planned for the enhanced WISE data include the search for nearby,
hidden cool stars, including those with masses as low as planets. If a large
planet or tiny star does exist close to our solar system, an object some call
"Tyche," then WISE's infrared data may reveal it.
Other
authors of the new study are: Daniel Gettings and Conor Mancone of the
University of Florida; Adam Stanford of Lawrence Livermore National Laboratory,
Livermore, Calif., and University of California, Davis; Mark Brodwin of
University of Missouri, Kansas City; Daniel Stern of JPL; Gregory Zeimann of
University of California, Davis; Frank Masci of the Infrared Processing and
Analysis Center at the California Institute of Technology, Pasadena; Casey
Papovich of Texas A&M University, College Station; Ichi Tanaka of the
National Astronomical Observatory of Japan; and Edward (Ned) Wright of UCLA.
JPL manages, and operated, WISE for NASA's Science Mission
Directorate. Edward Wright is the principal investigator and is at UCLA. The
mission was selected competitively under NASA's Explorers Program managed by
the agency's Goddard Space Flight Center in Greenbelt, Md. The science
instrument was built by the Space Dynamics Laboratory in Logan, Utah. The
spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder,
Colo. Science operations and data processing take place at the Infrared
Processing and Analysis Center at the California Institute of Technology in
Pasadena. Caltech manages JPL for NASA.
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