Andrew Yee
September 22nd 05, 04:46 PM
Joint Harvard-Smithsonian Center for Astrophysics-University of Texas at
Austin release
For more information, contact:
David A. Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam, Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
Rebecca Johnson, UT Austin
512-475-6763
Release No.: 05-31
For Immediate Release: Thursday, September 22, 2005
Ferreting Out The First Stars
Cambridge, MA -- What did the very first stars look like? How did they
live and die? Astronomers have ideas, but no proof. The first stars are so
distant and formed so long ago that they are invisible to our best
telescopes.
Until they explode. Hypernovas (more powerful cousins of supernovas) and
their associated gamma-ray bursts offer astronomers the possibility of
detecting light from the first generations of stars.
NASA's Swift satellite already has seen a gamma-ray burst (GRB) with a
redshift of 6.29, meaning that the progenitor star exploded about 13
billion years ago, when the universe was less than a billion years old.
Theorists Volker Bromm (University of Texas at Austin) and Avi Loeb
(Harvard-Smithsonian Center for Astrophysics) predict that one-tenth of
the blasts Swift will spot during its operational lifetime will come from
stars at a redshift of 5 or greater, that lived and died during the first
billion years of the universe.
"Most of those GRBs will come from second generation or later stars," said
Loeb. "But if we get lucky, Swift may even detect a burst from one of the
very first stars that formed -- a star made of only hydrogen and helium."
Calculations suggest that such stars, which are called Population III for
historical reasons, would have been behemoths weighing 50-500 times as
much as the Sun. A Population III star would have gulped its nuclear fuel
faster than an SUV, dying quickly and explosively.
"Our best guess right now is that the recent GRB was not from a Pop III
star. However, its redshift is high enough to make it very interesting,"
said Bromm.
One key question examined by Bromm and Loeb is whether a Pop III star
could have generated a GRB -- a blast powerful enough to be seen from a
distance of more than 13 billion light-years.
The answer they derived is a qualified yes. Pop III stars were massive
enough to explode violently, leaving behind a black hole in most cases.
However, a Pop III star likely would have to be part of a tight binary
system to generate a GRB.
A close binary companion could strip the outer layers of a dying Pop III
star, leaving less material to block the star's explosive death throes.
Jets of material generated from the newborn black hole therefore could
punch their way out more easily, creating a burst of gamma-ray energy
detectable across the universe.
About half of all nearby stars are members of binary or multiple star
systems. The frequency of binaries, particularly close binaries, among Pop
III stars remains unknown.
"Astronomers will address this question of the Pop III binary frequency
using a dual approach, both observational and theoretical," said Bromm.
"By searching for high-redshift GRBs, we can constrain that number
empirically. We also will try to improve simulations and make them
detailed enough to model those details of star formation."
If binary star systems are common among Pop III stars, then high-redshift
GRBs could offer astronomers an ideal opportunity to study the first
generation of stars.
"If Pop III binaries are common, Swift will be the first observatory to
probe Population III star formation at high redshifts," said Loeb.
This research has been submitted for publication to The Astrophysical
Journal and is available online at
http://arxiv.org/abs/astro-ph/0509303.
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 to editors:
High-resolution images to accompany this release are available online at
http://www.cfa.harvard.edu/press/pr0531image.html
Austin release
For more information, contact:
David A. Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam, Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
Rebecca Johnson, UT Austin
512-475-6763
Release No.: 05-31
For Immediate Release: Thursday, September 22, 2005
Ferreting Out The First Stars
Cambridge, MA -- What did the very first stars look like? How did they
live and die? Astronomers have ideas, but no proof. The first stars are so
distant and formed so long ago that they are invisible to our best
telescopes.
Until they explode. Hypernovas (more powerful cousins of supernovas) and
their associated gamma-ray bursts offer astronomers the possibility of
detecting light from the first generations of stars.
NASA's Swift satellite already has seen a gamma-ray burst (GRB) with a
redshift of 6.29, meaning that the progenitor star exploded about 13
billion years ago, when the universe was less than a billion years old.
Theorists Volker Bromm (University of Texas at Austin) and Avi Loeb
(Harvard-Smithsonian Center for Astrophysics) predict that one-tenth of
the blasts Swift will spot during its operational lifetime will come from
stars at a redshift of 5 or greater, that lived and died during the first
billion years of the universe.
"Most of those GRBs will come from second generation or later stars," said
Loeb. "But if we get lucky, Swift may even detect a burst from one of the
very first stars that formed -- a star made of only hydrogen and helium."
Calculations suggest that such stars, which are called Population III for
historical reasons, would have been behemoths weighing 50-500 times as
much as the Sun. A Population III star would have gulped its nuclear fuel
faster than an SUV, dying quickly and explosively.
"Our best guess right now is that the recent GRB was not from a Pop III
star. However, its redshift is high enough to make it very interesting,"
said Bromm.
One key question examined by Bromm and Loeb is whether a Pop III star
could have generated a GRB -- a blast powerful enough to be seen from a
distance of more than 13 billion light-years.
The answer they derived is a qualified yes. Pop III stars were massive
enough to explode violently, leaving behind a black hole in most cases.
However, a Pop III star likely would have to be part of a tight binary
system to generate a GRB.
A close binary companion could strip the outer layers of a dying Pop III
star, leaving less material to block the star's explosive death throes.
Jets of material generated from the newborn black hole therefore could
punch their way out more easily, creating a burst of gamma-ray energy
detectable across the universe.
About half of all nearby stars are members of binary or multiple star
systems. The frequency of binaries, particularly close binaries, among Pop
III stars remains unknown.
"Astronomers will address this question of the Pop III binary frequency
using a dual approach, both observational and theoretical," said Bromm.
"By searching for high-redshift GRBs, we can constrain that number
empirically. We also will try to improve simulations and make them
detailed enough to model those details of star formation."
If binary star systems are common among Pop III stars, then high-redshift
GRBs could offer astronomers an ideal opportunity to study the first
generation of stars.
"If Pop III binaries are common, Swift will be the first observatory to
probe Population III star formation at high redshifts," said Loeb.
This research has been submitted for publication to The Astrophysical
Journal and is available online at
http://arxiv.org/abs/astro-ph/0509303.
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 to editors:
High-resolution images to accompany this release are available online at
http://www.cfa.harvard.edu/press/pr0531image.html