HERSCHEL
SPACE OBSERVATORY FINDS OCEANS OF WATER IN PLANET-FORMING DISK AROUND NEARBY
STAR
From
NASA
Oct.
20, 2011
Using
data from the Herschel Space Observatory, astronomers have detected for the
first time cold water vapor enveloping a dusty disk around a young star. The
findings suggest that this disk, which is poised to develop into a solar
system, contains great quantities of water, suggesting that water-covered
planets like Earth may be common in the universe. Herschel is a European Space
Agency mission with important NASA contributions.
Scientists
previously found warm water vapor in planet-forming disks close to a central
star. Evidence for vast quantities of water extending out into the cooler, far
reaches of disks where comets take shape had not been seen until now. The more
water available in disks for icy comets to form, the greater the chances that
large amounts eventually will reach new planets through impacts. "Our
observations of this cold vapor indicate enough water exists in the disk to
fill thousands of Earth oceans," said astronomer Michiel Hogerheijde of
Leiden Observatory in The Netherlands. Hogerheijde is the lead author of a
paper describing these findings in the Oct. 21 issue of the journal Science.
The
star with this water-logged disk, called TW Hydrae, is 10 million years old and
located about 175 light-years away from Earth, in the constellation Hydra. The
frigid watery haze detected by Hogerheijde and his team is thought to originate
from ice-coated grains of dust near the disk's surface. Ultraviolet light from
the star causes some water molecules to break free of this ice, creating a thin
layer of gas with a light signature detected by Herschel's Heterodyne
Instrument for the Far-Infrared, or HIFI. "These are the most sensitive
HIFI observations to-date," said Paul Goldsmith, NASA project scientist
for the Herschel Space Observatory at the agency's Jet Propulsion Laboratory in
Pasadena , Calif.
"It is a testament to the instrument-builders that such weak signals can
be detected."
TW
Hydrae is an orange dwarf star, somewhat smaller and cooler than our
yellow-white sun. The giant disk of material that encircles the star has a size
nearly 200 times the distance between Earth and the sun. Over the next few
million years, astronomers believe matter within the disk will collide and grow
into planets, asteroids and other cosmic bodies. Dust and ice particles will
assemble as comets. As the new solar system evolves, icy comets are likely to
deposit much of the water they contain on freshly created worlds through
impacts, giving rise to oceans. Astronomers believe TW Hydrae and its icy disk
may be representative of many other young star systems, providing new insights
on how planets with abundant water could form throughout the universe.
[Where
there is water there should (eventually) be life – or so we suspect. If water
is as common as this observation suggests then it’s likely that rocky planets
outside of our Solar System might be expected to have liquid water on their
surface where conditions allow. As life on Earth almost certainly began in our
oceans this looks good for the emergence of life elsewhere. The evidence,
circumstantial though it is at present, keeps on piling up in favour of life
elsewhere.]
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