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Dim future for the Universe as stellar lights go out (Forwarded)



 
 
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Old August 12th 03, 04:25 PM
Andrew Yee
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Default Dim future for the Universe as stellar lights go out (Forwarded)

Royal Astronomical Society Press Notice
London, U.K.

Issued by: Jacqueline Mitton, RAS Press Officer
, tel: +44 (0)1223-564914

CONTACTS:

Prof Alan Heavens
Institute for Astronomy, University of Edinburgh
Phone: (+44) (0)131 668 8352
e-mail:


Prof Raul Jimenez
Assistant Professor of Physics & Astronomy
Dept of Physics & Astronomy, University of Pennsylvania
Phone: +1-215-573-5630
Fax : +1-215-898-2010
e-mail:


Date: 7 August 2003

PN03-32

DIM FUTURE FOR THE UNIVERSE AS STELLAR LIGHTS GO OUT

The universe is gently fading into darkness according to three astronomers who
have looked at 40,000 galaxies in the neighbourhood of the Milky Way. Research
student Ben Panter and Professor Alan Heavens from Edinburgh University's
Institute for Astronomy, and Professor Raul Jimenez of University of
Pennsylvania, USA, decoded the "fossil record" concealed in the starlight from
the galaxies to build up a detailed account of how many young, recently-formed
stars there were at different periods in the 14-billion-year existence of the
universe. Their history shows that, for billions of years, there have not been
enough new stars turning on to replace all the old stars that die and switch
off. The results will be published in the Monthly Notices of the Royal
Astronomical Society on 21 August 2003.

"Our analysis confirms that the age of star formation is drawing to a close",
says Alan Heavens. "The number of new stars being formed in the huge sample of
galaxies we studied has been in decline for around 6 billion years -- roughly
since the time our own Sun came into being."

Astronomers already had evidence that this was the case, mainly from observing
galaxies so far away that we see them as they were billions of years ago because
of the great length of time their light has taken to reach us. Now the same
story emerges strongly from the work of Panter, Heavens and Jimenez, who for the
first time approached the problem differently and used the whole spectrum of
light from an enormous number of nearby galaxies to get a more complete picture.

Galaxies shine with the combined light of all the stars in them. Most of the
light from young stars is blue, coming from very hot massive stars. These blue
stars live fast and die young, ending their lives in supernova explosions. When
they have gone, they no longer outshine the smaller red stars that are more
long-lived. Many galaxies look reddish overall rather than blue -- a broad sign
that most star formation happened long ago.

In their analysis, Panter, Heavens and Jimenez have used far more than the
simple overall colours of the galaxies, though. The spectrum observations they
used come from the Sloan Digital Sky Survey and the volume of data involved was
so vast, that the researchers had to develop a special lossless data compression
method, called MOPED, to allow them to analyse the sample in a reasonable length
of time, without losing accuracy.

NOTE

More information about the Sloan Digital Sky Survey may be obtained from
http://www.sdss.org

 




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