NASA's
Spitzer Space Telescope has revealed a dusty star system being soaked with a
"steamy rain" of water vapor.
The water,
pulled from gassy stellar leftovers into a dusty disk, provides what
astronomers think is the first direct look at how the life-giving liquid makes
its way into planets. The disk is the same sort of thing that forms around many
stars and, in the case of our sun, was the seedbed for planet formation.
The amount
of water in the newly observed disk is thought to equal more than five times
that of all oceans on Earth.
"For
the first time, we are seeing water being delivered to the region
where planets will most likely form," said Dan Watson, an
astrophysicist at the University of Rochester in New York.
Watson and
his colleagues' work will be detailed in the Aug. 30 issue of the journal Nature.
Steamy
surprise
Water is
abundant throughout our universe, existing as ice or gas around stars and in
the space between stars, but rarely as a liquid.
"On
Earth, water arrived in the form of icy asteroids and comets," Watson
said. "Water also exists mostly as ice in the dense clouds that form
stars."
Astronomers
found the watery evidence in a young star system called NGC 1333-IRAS 4B, located
1,000 light-years away in the constellation Perseus. The system still grows
inside a cooled cocoon of gas and dust, and Spitzer data show that ice is
falling from the cocoon into a warm disk of potential planet-forming
materials circling the star.
As the ice
smacks into the dust, it vaporizes.
"Now
we've seen that water, falling as ice from a young star system's envelope to
its disk, actually vaporizes on arrival," Watson said. "This water
vapor will later freeze again into asteroids and comets."
Dry
search
Watson and
his team's discovery comes after a detailed look at 30 similarly young star
systems with Spitzer's infrared spectrograph, an instrument that reveals
"fingerprints" of molecules like water. Of the 30 stellar embryos
investigated, only NGC 1333-IRAS 4B harbors significant amounts of water.
The dry
search, however, may not be due to a lack of water in the other star systems,
the astronomers explained. NGC 1333-IRAS 4B is in just the right orientation
for Spitzer to view its dense core and, they added, such a watery phase is
short-lived and hard to catch.
"We
have captured a unique phase of a young star's evolution, when the stuff of life
is moving dynamically into an environment where
planets could form," said Michael Werner, a project scientist with the
Spitzer mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The
astronomers explained that water serves as an important tool for studying the planet
formation process, which is not very well understood.
"Water
is easier to detect than other molecules, so we can use it as a probe to look
at more brand-new disks and study their physics and chemistry," said
Watson. "This will teach us a lot about how
planets form."
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