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<H3 class=entry-header><A
href="http://www.dailygalaxy.com/my_weblog/2008/08/vals-sunday-pos.html"><FONT
face=Verdana size=5>Massive Radio-telescope in China to Explore 'Dark Age' of
Early Universe</FONT></A></H3>
<DIV class=entry-content>
<DIV class=entry-body>
<P><A
href="http://www.dailygalaxy.com/photos/uncategorized/2008/08/03/123752main_pia03538browse_2.jpg"><FONT
face=Verdana size=3></FONT></A><FONT face=Verdana size=3> <FONT
size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">Astronomers
in the <?xml:namespace prefix = st1 ns =
"urn:schemas-microsoft-com:office:smarttags" /><st1:country-region
w:st="on">U.S.</st1:country-region> and <st1:country-region
w:st="on">China</st1:country-region> are also building an enormous
radiotelescope array consisting of about 10,000 antennas in <st1:country-region
w:st="on">China</st1:country-region>'s <st1:place w:st="on"><st1:PlaceName
w:st="on">Xinjiang</st1:PlaceName> <st1:PlaceType
w:st="on">Province</st1:PlaceType></st1:place>. They plan to use it to map the
first glowing "bubbles" that appear as radiation from galaxies begins to ionize
the dense fog of hydrogen between them and light it up. </SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><?xml:namespace
prefix = o ns = "urn:schemas-microsoft-com:office:office"
/><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">"The
only way we're ever going to understand this is when the theoretical work that's
progressing rapidly in this field meets up with the observations work, which is
coming from the other direction" of the timeline, says Elizabeth Barton, an
astronomer at the University of California at Irvine.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">"It's
a big puzzle," she adds, and the new results, which appear in Friday's edition
of the journal Science, represent a small but important piece.</SPAN><SPAN
lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">Researchers
reported they have glimpsed – using computer simulations – the birth of the
first small, stable clumps of gas that would have served as seeds for the first
generation of stars. Within 10,000 years, the scientists say, these seeds would
blossom into blazing orbs at least 100 times more massive than the
sun.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
new study is part of a broader effort to understand the early years of the
universe, after the big bang using computer simulations can help scientists
understand events like the birth of the first stars in the universe. During much
of the universe's first billion years, the awesome brilliance born of the big
bang faded to black. This dark age represents the least-understood chapter in
the history of the cosmos scientists have compiled.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">"We
have a good understanding of what the universe looked like shortly after it
originated about 14 billion years ago. We also have a good idea of what the
universe looks like now," says Lars Hernquist, a <st1:place
w:st="on"><st1:PlaceName w:st="on">Harvard</st1:PlaceName> <st1:PlaceType
w:st="on">University</st1:PlaceType></st1:place> astrophysicist and member of
the team. "But there's a significant gap in our understanding of how the
universe made this transition from what it looked like after the big bang to how
it appears to us today."</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
model follows the simpler physics that ruled the early universe to see how cold
clumps of gas eventually grew into giant star embryos.<BR><BR>"Until you put
that physics in the code, you can't evaluate how the first protostars formed,"
said Lars Hernquist, an astrophysicist at <st1:place w:st="on"><st1:PlaceName
w:st="on">Harvard</st1:PlaceName> <st1:PlaceType
w:st="on">University</st1:PlaceType></st1:place> whose early-stars model is
detailed in this week's issue of the journal Science. His remarks were made
Wednesday during a press teleconference.<BR><BR>Mysterious "dark matter"
provided the first gravitational impetus for hydrogen and helium gas to start
clumping together, Hernquist said. The gas began releasing energy as it
condensed, forming molecules from atoms, which further cooled the clump and
allowed for even greater condensing.<BR><BR>Unlike previous models, the latest
simulation takes this cooling process of "complex radiative transfer" into
account, said <st1:place w:st="on"><st1:PlaceName
w:st="on">Nagoya</st1:PlaceName> <st1:PlaceType
w:st="on">University</st1:PlaceType></st1:place> astrophysicist Naoki Yoshida,
who headed up the modeling project.<BR><BR>Eventually gravity could not condense
the gas cloud any further, because the densely-packed gas exerted a pressure
against further collapse. That equilibrium point marked the beginning of an
embryonic star, called a protostar by astronomers.<BR><BR>Simulation runs show
that the first protostar likely started with just 1 percent the mass of our sun,
but would have swelled to more than 100 solar masses in 10,000 years.<BR><BR>"No
simulation has ever gotten to the point of identifying this important stage in
the birth of a star," Hernquist noted.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">Until
new tools can peer more deeply into that gap, simulations remain the only
vehicles for exploring the transition.<BR><BR>The simulation is part of an
international effort to fill the dark-age gap. Astronomers worldwide are pushing
ground-based optical telescopes to their limits, building vast radiotelescope
arrays and looking to a new generation of space- and ground-based telescopes to
probe this crucial period. </SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
nuclear furnaces in the first stars would have formed the first atoms of carbon,
silicon, oxygen, and other heavy elements, researchers hold. These elements
would become incorporated into later generations of stars, which in turn would
add their contributions to the chemical inventory.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">Over
time, clusters of stars would form galaxies whose combined radiation would
eventually shift the cosmos from opaque to transparent. The heavier elements the
stars forged and launched into the cosmos would form basic organic and inorganic
molecules, and become the raw material for planets.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
research team started with a universe dominated by recently discovered dark
energy and by cold dark matter, which astronomers currently detect by its
gravitational influence on matter they can see. Hydrogen dominates the small
percentage of "normal" matter in this young, denser universe. It's in a form
that renders it opaque to light.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
simulation picks up the story when the universe was roughly 300 million years
old and 20 times more compact that it is today. The afterglow of the big bang
had long since faded. Subtle variations in the density of dark matter across
space led to regions where dark matter was more dense than others.</SPAN><SPAN
lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
simulation focuses on one of these denser areas, or halos. There, dark matter's
enhanced gravity corrals hydrogen. The hydrogen cloud undergoes alternate
periods of heating and cooling as it contracts due to gravitational collapse. It
also shifts from cloud to flattened disk and finally to a stable sphere of a
proto-star.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">At
this stage, with 1 percent of the sun's mass (or about 10 times Jupiter's mass),
the proto-star's internal temperature has risen high enough to generate an
outward pressure that prevents further collapse.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
stimulation stops there, but additional calculations suggest that within 1,000
years, the proto-star would have grown into a star 10 times more massive than
the sun. By 10,000 years, the star would have topped 100 times the sun's
mass.</SPAN><SPAN lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">Such
huge stars are thought to have lived only for about 1 million years, compared
with an expected lifetime of roughly 10 billion years for the sun.</SPAN><SPAN
lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><FONT size=2><SPAN lang=EN-GB
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'">The
new work also traces the formation of the first stable proto-stars. No star
could form without these stable proto-stars, even in today's universe, Dr.
Hernquist says. The researchers eventually hope to run the simulation all the
way up through the point where protostars ignite into true stars.</SPAN><SPAN
lang=EN-GB
style="FONT-SIZE: 24pt; FONT-FAMILY: Verdana; mso-font-kerning: 18.0pt; mso-ansi-language: EN-GB; mso-bidi-font-weight: bold"><o:p></o:p></SPAN></FONT></P>
<P style="mso-outline-level: 2"><SPAN
style="FONT-FAMILY: Verdana; mso-fareast-font-family: 'Arial Unicode MS'; mso-font-kerning: 18.0pt; mso-bidi-font-weight: bold; mso-bidi-font-family: 'Arial Unicode MS'"><FONT
size=2>Posted by Casey Kazan in</FONT></SPAN><SPAN
style="FONT-FAMILY: Verdana"><o:p> <FONT face=Arial><A
href="http://www.dailygalaxy.com/my_weblog/">http://www.dailygalaxy.com/my_weblog/</A></FONT></o:p></SPAN></P>
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