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For Release: Thursday, July 31, 2008

Release No.: 2008-14

The First Stars

Cambridge, MA -- The universe began with the Big Bang about 13.7 billion
years ago. Very soon after that event, the first stars formed. Today, those
stars are dead and gone leaving little evidence of their size and
composition behind. Now, a new computer simulation now offers the most
detailed picture yet of how these first stars came into existence. These
findings will be published by the journal Science on Friday, 1 August. The
composition of the early universe was quite different from that of today,
and the physics that governed the early universe were also somewhat simpler.
Dr. Naoki Yoshida, Nagoya University in Nagoya, Japan and co-author Dr. Lars
Hernquist at the Harvard-Smithsonian Center for Astrophysics in Cambridge,
MA, incorporated these conditions of the early universe, sometimes referred
to as the "cosmic dark ages," to simulate the formation of an astronomical
object that would eventually shine as a star.

According to their simulations, gravity acted on minute density variations
in matter, gases, and the mysterious "dark matter" of the
universe after the
Big Bang in order to form the early stages of a star called a protostar.
With a mass of just one percent of our Sun, Dr. Yoshida's simulation also
shows that the protostar would likely evolve into a massive star capable of
synthesizing heavy elements, not just in later generations of stars, but
soon after the Big Bang. These stars would have been up to one hundred times
as massive as our Sun and would have burned for no more than one million
years. "This general picture of star formation, and the ability to compare
how stellar objects form in different time periods and regions of the
universe, will eventually allow investigation in the origins of life and
planets," said Hernquist.

"The abundance of elements in the Universe has increased as stars have
accumulated," he says, "and the formation and destruction of
stars continues
to spread these elements further across the Universe. So when you think
about it, all of the elements in our bodies originally formed from nuclear
reactions in the centers of stars, long ago." Their simulation of the birth
of a protostar in the early universe signifies a key step toward the
ambitious goal of piecing together the formation of an entire primordial
star and of predicting the mass and properties of these first stars of the
universe. More powerful computers, more physical data, and an even larger
range will be needed for further calculations and simulations, but these
researchers hope to eventually extend this simulation to the point of
nuclear reaction initiation -- when a stellar object becomes a true star.

"Dr. Yoshida has taken the study of primordial star formation to a new level
with this simulation, but it still gets us only to the halfway point towards
our final goal. It is like laying the foundation of a skyscraper," said
Volker Bromm, Assistant Professor of Astronomy at the University of Texas,
Austin and the author of a companion article. "We must continue our studies
in this area to understand how the initially tiny protostar grows, layer by
layer, to eventually form a massive star. But here, the physics become much
more complicated and even more computational resources are needed."

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.

[NOTE: An image supporting this release is available at
http://cfa-www.harvard.edu/press/2008/pr200814_images.html ]
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