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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
(7×1022) 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."
ANU MEDIA OFFICE CONTACT: Tim Winkler (02) 6125 5001/0416 249 231
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