Aging Universe May Still Be Spawning Massive Galaxies
NASA's Galaxy Evolution Explorer has spotted what appear to be
massive "baby" galaxies in our corner of the universe. Previously,
astronomers thought the universe's birth rate had dramatically
declined and only small galaxies were forming.
Image right: This animation shows a typical young galaxy, teeming with hot, newborn stars and exploding supernovas. The supernovas are seen as white flashes of light. Click for animation.
"We knew there were really massive young galaxies eons ago, but we
thought they had all matured into older ones more like our Milky
Way. If these galaxies are indeed newly formed, then this implies
parts of the universe are still hotbeds of galaxy birth," said Dr.
Chris Martin. He is principal investigator for the Galaxy Evolution
Explorer at the California Institute of Technology, Pasadena,
Calif., and co-author of the study.
Martin and colleagues, led by Dr. Tim Heckman of Johns Hopkins
University, Baltimore, Md., unearthed three-dozen bright, compact
galaxies that greatly resemble the youthful galaxies of more than 10
billions years ago. These new galaxies are relatively close to us,
ranging from two to four billion light-years away. They may be as
young as 100 million to one billion years old. The Milky Way is
approximately 10 billion years old.
Image above: This artist's conception illustrates the decline in our universe's "birth-rate" over time. When the universe was young, massive galaxies were forming regularly, like baby bees in a bustling hive. In time, the universe bore fewer and fewer "offspring," and newborn galaxies (white circles) matured into older ones more like our own Milky Way (spirals). Click for full caption.
The recent discovery suggests our aging universe is still alive with
youth. It also offers astronomers their first, close-up glimpse at
what our galaxy probably looked like when it was in its infancy.
"Now we can study the ancestors to galaxies much like our Milky Way
in much more detail than ever before," Heckman said. "It's like
finding a living fossil in your own backyard. We thought this type
of galaxy had gone extinct, but in fact newborn galaxies are alive
and well in the universe," he added.
The new discoveries are of a type called ultraviolet luminous
galaxies. They were discovered after the Galaxy Evolution Explorer
scanned a large portion of the sky with its highly sensitive
ultraviolet light detectors. Since young stars pack most of their
light into ultraviolet wavelengths, young galaxies appear to the
spacecraft like diamonds in a field of stones. Astronomers mined for
these rare gems before, but missed them because they weren't able to
examine a large enough slice of the sky.
"The Galaxy Evolution Explorer surveyed thousands of galaxies before
finding these few dozen ultraviolet-bright ones," said Dr. Michael
Rich, a co-author of the study from the University of California,
The newfound galaxies are about 10 times as bright in ultraviolet
wavelengths as the Milky Way. This indicates they are teeming with
violent star-forming regions and exploding supernova, which are
characteristics of youth.
When our universe was young, massive galaxies were regularly
bursting into existence. Over time, the universe bore fewer and
fewer galactic progeny, and its newborn galaxies grew up into ones
that look like our own. Until now, astronomers thought they had seen
the last of these giant babies.
The results will be published in an upcoming special issue of
Astrophysical Journal Letters, along with several other papers
describing new results from the Galaxy Evolution Explorer.
The Galaxy Evolution Explorer was launched on April 28, 2003. Its
mission is to study the shape, brightness, size and distance of
galaxies across 10 billion years of cosmic history. The Explorer's
50-centimeter-diameter (19.7-inch) telescope sweeps the skies in
search of ultraviolet-light sources.
Caltech leads the Galaxy Evolution Explorer mission and is
responsible for science operations and data analysis. NASA's Jet
Propulsion Laboratory, Pasadena, Calif., manages the mission and
built the science instrument. The mission was developed under NASA's
Explorers Program managed by the Goddard Space Flight Center,
Greenbelt, Md. South Korea and France are the international partners
in the mission.
For images and information about the Galaxy Evolution Explorer on
the Internet, visit
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Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
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NASA Headquarters, Washington, D.C.