by Melissa Gray
September 3, 2010
The dying star IRC+10216
is surrounded by a large volume of
high-temperature water vapor.
London, England (CNN)
European scientists say they've figured out
the recipe for water in space: Just add starlight.
They made the discovery while examining a dying star that is 500
light-years away from Earth, using an infrared observatory launched
by the European Space Agency last year.
"This is a good example of how better instruments can change our
picture completely," said Leen Decin of the Catholic University of
Leuven in Belgium, who is the lead author of the paper about the
The story begins in 2001, when astronomers discovered an unexpected
cloud of water vapor around an old star called
is known as a carbon star, not thought to make much water, so
scientists initially thought the star's heat must have evaporated
comets or dwarf planets to produce the water vapor.
European Space Agency's Herschel laboratory launched last
year, however, scientists discovered spectral lines in the light
coming from the water vapor.
"Some of these lines can only be there if the temperature is high,
otherwise we wouldn't see them," said Goran Pilbratt, a project
scientist for the Herschel space observatory. "None of them have
been seen before."
Those spectral lines gave scientists a vital clue: The water was
hot, with temperatures as high as 800 degrees Celsius (nearly 1,500
That meant the water was too hot to have been
formed by the destruction of icy celestial bodies, and had to have
been formed much closer to the star than comets could stably exist.
So if the water wasn't the result of comets being blasted apart as
they passed by, scientists wondered, where did it come from?
The water vapor sits in a dusty cloud surrounding IRC+10216.
Scientists deduced that ultraviolet light from surrounding stars had
penetrated that dusty cloud, breaking up molecules in it like carbon
monoxide and silicon monoxide, which in turn released oxygen atoms.
Those oxygen atoms attached themselves to hydrogen molecules,
"The ultraviolet light didn't create it - it helped it to be
formed," Pilbratt told CNN.
Ultraviolet light is the only way water could have been produced in
such conditions, he said.
IRC+10216 is a red giant star, hundreds of times the sun's size, the
European Space Agency said. If it replaced the sun in our solar
system, it would extend beyond the orbit of Mars.
The star is barely detectable at visible wavelengths because of that
huge cloud of dust surrounding it. It can be seen at some infrared
wavelengths, however, because the dust cloud absorbs almost all of
the star's visible radiation and re-emits it as infrared light.
Scientists now hope to observe other carbon stars.
"We are very
hopeful that Herschel will find the same situations around those
stars too," Decin said.