Star count: Australian National U. astronomer makes best yet (Forwarded)

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Thursday, 17 July 2003

STAR COUNT: ANU ASTRONOMER MAKES BEST YET

There are more stars in the sky than all the grains of sand on every beach and
in every desert on earth, according to an Australian National University
astronomer who has made the most accurate calculation of star numbers to date.

Dr Simon Driver, of the ANU Research School of Astronomy and Astrophysics, using
some of the most powerful telescopes in the world, concluded that about 70
thousand million million million stars (7×10**22) shine down on us each night.

"Even for a professional astronomer used to dealing in monster numbers this is
mind-boggling," Dr Driver says.

Most of these stars are too dim to see with the naked human eye, which can pick
out only around 5,000 stars at the darkest parts of earth and just 100 in the
middle of a big city, such as Sydney.

Dr Driver and his collaborators -- Dr Jochen Liske, from the Royal Observatory
Edinburgh; Dr Nicholas Cross, from Johns Hopkins University; Professor Warrick
Couch, from the University of New South Wales and Dr David Lemon from St Andrews
University -- did not count the stars one by one.

Rather, Dr Driver and his team counted all the galaxies, which are large
collections of stars, in one small region of the universe close to Earth.

By measuring precisely how bright each galaxy is they were able to estimate how
many stars it contained and extrapolated this out to the whole region of the
Universe visible through telescopes.

The researchers, who will present their finding to the General Assembly of the
International Astronomical Union today, believe their estimate is ten times more
accurate than any previous count.

"This is not the total number of stars in the universe, but it's the number
within range of our telescopes. The real number could be much, much larger still
-- some people think it is infinite."

There have been other estimates of the number of stars over the years, but Dr
Driver's calculation is the closest so far because it combines the best counts
of galaxies ever conducted with the most modern cosmological measurements of the
geometry of our universe.

The observations were carried out using many of the world's most powerful
telescopes, including the Anglo-Australian Telescope, located at the
University's Siding Spring Observatory, near the town of Coonabarabran. The
calculations would not have been possible without the world's largest galaxy
survey, the 2dF Galaxy Redshift Survey, which will be released at this meeting.

"Most of these stars probably have planets, a fraction of which probably have
life," Dr Driver says.

"But they are very, very far away. It's not so much a question of whether other
life exists, but whether we will ever be able to contact them given the massive
distances involved."

Andrew Yee wrote:

There are more stars in the sky than all the grains of sand on every
beach and in every desert on earth, according to an Australian
National University astronomer who has made the most accurate
calculation of star numbers to date.

I'll delurk long enough to point out that I posted an order of magnitude
estimate of the stars/sand ratio to sci.astro.amateur several years ago,
and it's pretty close to 1.0. See

http://www.google.com/groups?selm=37...E65%40home.com
http://www.google.com/groups?selm=3A...97A%40home.com

"Even for a professional astronomer used to dealing in monster numbers
this is mind-boggling," Dr Driver says.

People enjoy being boggled, I guess. Hopefully it doesn't diminish the
grandeur of the universe to realize that we can find numbers of this
size in things, like sand grains, that are closer to human scale.

- Ernie http://mywebpages.comcast.net/erniew

In message , Ernie Wright
writes
Andrew Yee wrote:

There are more stars in the sky than all the grains of sand on every
beach and in every desert on earth, according to an Australian
National University astronomer who has made the most accurate
calculation of star numbers to date.

I'll delurk long enough to point out that I posted an order of magnitude
estimate of the stars/sand ratio to sci.astro.amateur several years ago,
and it's pretty close to 1.0. See

http://www.google.com/groups?selm=37...E65%40home.com
http://www.google.com/groups?selm=3A...97A%40home.com

"Even for a professional astronomer used to dealing in monster numbers
this is mind-boggling," Dr Driver says.

People enjoy being boggled, I guess. Hopefully it doesn't diminish the
grandeur of the universe to realize that we can find numbers of this
size in things, like sand grains, that are closer to human scale.

A chemist probably wouldn't be impressed :-) It's roughly the number of
atoms in 1 gram of carbon, if I've done my sums right.
--
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relativity"
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