Astronomers Eye Ultra-Young, Bright Galaxy in Early Universe For…

 Astronomers Eye Ultra-Young, Bright Galaxy in Early Universe
For Release: February 12, 2008


NASA's Hubble and Spitzer space telescopes, with a boost from a natural "zoom
lens," have uncovered what may be one of the youngest and brightest galaxies
ever seen in the middle of the cosmic "dark ages," just 700 million years after
the beginning of our universe.

The detailed images from Hubble's Near Infrared Camera and Multi-Object
Spectrometer reveal an infant galaxy, dubbed A1689-zD1, undergoing a
firestorm of star birth during the dark ages, a time shortly after the Big Bang but
before the first stars reheated the cold, dark universe. Images from NASA's
Spitzer Space Telescope's Infrared Array Camera provided strong additional
evidence that it was a young star-forming galaxy in the dark ages.

"We certainly were surprised to find such a bright young galaxy 12.8 billion
years in the past," said astronomer Garth Illingworth of the University of
California, Santa Cruz, and a member of the research team. "This is the most
detailed look to date at an object so far back in time."

"The Hubble images yield insight into the galaxy's structure that we cannot get
with any other telescope," added astronomer Rychard Bouwens of UC Santa
Cruz, a co-discoverer. The new images should offer insights into the formative
years of galaxy birth and evolution and yield information on the types of objects
that may have contributed to ending the dark ages. The faraway galaxy also is
an ideal target for Hubble's successor, the James Webb Space Telescope,
scheduled to launch in 2013.

During its lifetime, the Hubble telescope has peered ever farther back in time,
viewing galaxies at successively younger stages of evolution. These snapshots
have helped astronomers create a scrapbook of galaxies from infancy to
adulthood. The new Hubble and Spitzer images of A1689-zD1 show a time
when galaxies were in their infancy.

Current theory holds that the dark ages began about 400,000 years after the Big
Bang, as matter in the expanding universe cooled and formed clouds of cold
hydrogen. These cold clouds pervaded the universe like a thick fog. At some
point during this era, stars and galaxies started to form. Their collective light
reheated the foggy, cold hydrogen, ending the dark ages about a billion years
after the Big Bang.
"This galaxy presumably is one of the many galaxies that helped end the dark
ages," said astronomer Larry Bradley of Johns Hopkins University in Baltimore,
Md., and leader of the study. "Astronomers are fairly certain that high-energy
objects such as quasars did not provide enough energy to end the dark ages of
the universe. But many young star-forming galaxies may have produced enough
energy to end it."

The galaxy is so far away it did not appear in images taken with Hubble's
Advanced Camera for Surveys, because its light is stretched to invisible infrared
wavelengths by the universe's expansion. It took Hubble's near infrared
camera/spectrometer, Spitzer, and a trick of nature called gravitational lensing
to see the faraway galaxy. The astronomers used a relatively nearby massive
cluster of galaxies known as Abell 1689, roughly 2.2 billion light-years away, to
magnify the light from the more distant galaxy directly behind it. This natural
telescope is called a gravitational lens.

Though the diffuse light of the faraway object is nearly impossible to see,
gravitational lensing has increased its brightness by nearly 10 times, making it
bright enough for Hubble and Spitzer to detect. A telltale sign of the lensing is
the smearing of the images of galaxies behind Abell 1689 into arcs by the
gravitational warping of space by the intervening galaxy cluster.

The images reveal bright, dense clumps of hundreds of millions of massive stars
in a compact region about 2,000 light-years across, which is only a fraction of
the width of our Milky Way Galaxy. This type of galaxy is not uncommon in the
early universe, when the bulk of star formation was taking place, Bradley and
Illingworth said.

Spitzer's images show the galaxy's mass is typical of galaxies in the early
universe. Its mass is equivalent to several billions of sunlike stars, or just a tiny
fraction of the mass of the Milky Way. "This observation confirms previous
Hubble studies that star birth happens in very tiny regions compared with the
size of the final galaxy," Illingworth said.

Even with the increased magnification from the gravitational lens, Hubble's
sharp "eye" can only see knots of the brightest, heftiest stars in the galaxy. The
telescope cannot pinpoint fainter, lower-mass stars, individual stars, or the
material surrounding the star-birthing region. To see those things, astronomers
will need the infrared capabilities of the Webb Telescope. The planned infrared
observatory will have a mirror about seven times the area of Hubble's primary
mirror and will collect more light from faint galaxies. It also will be able to view
even more remote galaxies whose light has been stretched deep into infrared
wavelengths that are out of the reach of Hubble.

Team member Holland Ford of Johns Hopkins University said this galaxy will be
one of the first objects the Webb Telescope will observe, saying, "This object is a
pathfinder for the James Webb Space Telescope for deciphering what is
happening in young galaxies." The astronomers noted that the faraway galaxy
also would be an ideal target for the Atacama Large Millimeter Array, which,
when completed in 2012, will be the world's most powerful radio telescope.
The results will appear in the Astrophysical Journal, with followup observations
planned with Hawaii's Keck telescope.

The Space Telescope Science Institute conducts science operations for Hubble, a
project of international cooperation between NASA and the European Space
Agency. The institute is operated for NASA by the Association of Universities for
Research in Astronomy, Inc., Washington. The Jet Propulsion Laboratory,
Pasadena, Calif., manages Spitzer for NASA's Science Mission Directorate.
Science operations are conducted at the Spitzer Science Center at the California
Institute of Technology, which manages JPL for NASA.