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First Supernovae Quickly Seeded Universe With Stuff Of Life



 
 
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Old September 19th 03, 04:20 AM
Ron Baalke
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Default First Supernovae Quickly Seeded Universe With Stuff Of Life

http://cfa-www.harvard.edu/press/pr0321.html

Harvard-Smithsonian Center for Astrophysics
Release No.: 03-21
For Release: September 18, 2003

First Supernovae Quickly Seeded Universe With Stuff Of Life

Note to Editors: Animations and an image are available at:
http://cfa-www.harvard.edu/press/pr0321image.html

The early universe was a barren wasteland of hydrogen, helium, and a touch
of lithium, containing none of the elements necessary for life as we know
it. From those primordial gases were born giant stars 200 times as massive
as the Sun, burning their fuel at such a prodigious rate that they lived
for only about 3 million years before exploding. Those explosions spewed
elements like carbon, oxygen and iron into the void at tremendous speeds.
New simulations by astrophysicists Volker Bromm (Harvard-Smithsonian
Center for Astrophysics), Naoki Yoshida (National Astronomical Observatory
of Japan) and Lars Hernquist (CfA) show that the first, "greatest
generation" of stars spread incredible amounts of such heavy elements
across thousands of light-years of space, thereby seeding the cosmos with
the stuff of life.

This research is posted online at http://arxiv.org/abs/astro-ph/0305333
and will be published in an upcoming issue of The Astrophysical Journal
Letters.

"We were surprised by how violent the first supernova explosions were,"
says Bromm. "A universe that was in a pristine state of tranquility was
rapidly and irreversibly transformed by a colossal input of energy and
heavy elements, setting the stage for the long cosmic evolution that
eventually led to life and intelligent beings like us."

Approximately 200 million years after the Big Bang, the universe underwent
a dramatic burst of star formation. Those first stars were massive and
fast-burning, quickly fusing their hydrogen fuel into heavier elements
like carbon and oxygen. Nearing the end of their lives, desperate for
energy, those stars burned carbon and oxygen to form heavier and heavier
elements until reaching the end of the line with iron. Since iron cannot
be fused to create energy, the first stars then exploded as supernovae,
blasting the elements that they had formed into space.

Each of those first giant stars converted about half of its mass into
heavy elements, much of it iron. As a result, each supernova hurled up to
100 solar masses of iron into the interstellar medium. The death throes of
each star added to the interstellar bounty. Hence, by the remarkably young
age of 275 million years, the universe was substantially seeded with
metals.

That seeding process was aided by the structure of the infant universe,
where small protogalaxies less than one-millionth the mass of the Milky
Way crammed together like people on a crowded subway car. The small sizes
of and distances between those protogalaxies allowed an individual
supernova to rapidly seed a significant volume of space.

Supercomputer simulations by Bromm, Yoshida, and Hernquist showed that the
most energetic supernova explosions sent out shock waves that flung heavy
elements up to 3,000 light-years away. Those shock waves swept huge
amounts of gas into intergalactic space, leaving behind hot "bubbles," and
triggered new rounds of star formation.

Supernova expert Robert Kirshner (CfA) says, "Today this is a fascinating
theory, based on our best understanding of how the first stars worked. In
a few years, when we build the James Webb Space Telescope, the successor
to the Hubble Space Telescope, we should be able to see these first
supernovae and test Volker's ideas. Stay tuned!"

Lars Hernquist notes that the second generation of stars contained heavy
elements from the first generation - seeds from which rocky planets like
Earth could grow. "Without that first, 'greatest generation' of stars, our
world would not exist."

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics 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.

For more information, contact:

David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468


Christine Lafon
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016


 




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