BEIJING, July 26 (Xinhuanet) -- Astronomers working
with NASA's infrared Spitzer Telescope have located a swirling disk in a
four-star solar system that could be home to a planet in the making.
Astronomers spotted the disk around a pair of stars in the quadruple-star system HD 98800, located 150
light-years away in the constellation TW Hydrae. The finding will be detailed in
an upcoming issue of The Astrophysical Journal.
If a planet did form in the disk, its sky would be
bathed in the light of four suns. One pair of suns would blaze brightly, while
the other pair, gravitationally bound to the first pair, would appear as little
more than faint pinpoints of light.
So-called "circumstellar" disks like the one that
rings HD 98800 can be the birthplace of planets. Most disks are smooth and
continuous, but the Spitzer detected a gap in the HD 98800 disk that could be
evidence of one or more immature "protoplanets" carving out lanes in the
dust.
"Planets are like cosmic vacuums," said study team
member Elise Furlan of the NASA Astrobiology Institute at the University of
California, Los Angeles. "They clear up all the dirt that is in their path
around the central stars."
The researchers spied two separate belts of material
in the circumstellar disk. One belt sits at 1.5 to 2 astronomical units (AU) --
the distance between the Earth and sun -- from the binary stars and likely
consists of fine dust grains. The other is located about 5.9 AU away from and is
probably made up of asteroids or comets. A swath of near-empty space
separates the two belts, inside of which a budding planet might roam.
Alternatively, the researchers think the gap could be
caused by a gravitational tug-of-war between the system's four stars. The other
two stars are also doubled up, and the two binary pairs are separated by about
50 AU -- slightly more than the distance between our sun and Pluto.
"Typically, when astronomers see gaps like this in a
debris disk, they suspect that a planet has cleared a path," Furlan said.
"However, given the presence of the diskless pair of stars sitting 50 AU away,
the inward-migrating dust particles are likely subject to complex, time-varying
forces, so at this point the existence of a planet is just speculation."
(Agencies)
