New
worlds no longer so alien
Technology
helps scientists rapidly detect exoplanets
July
25, 2007
BY ROBERT
S. BOYD
MCCLATCHY
NEWSPAPERS
WASHINGTON
-- It's boom time for planet hunters. Astronomers are bagging new worlds at an
average rate of more than two a month.
As
of Friday, the latest available date, 246 extrasolar planets had been detected
circling other stars in the Milky Way galaxy. Among them are 25 alien solar systems
consisting of two, three or four bodies orbiting single suns.
Four
new exoplanets, as they're also called, were reported this month; three were reported
in May and 28 during the last 12 months. The smallest known exoplanet, only twice
as wide and five times heavier than Earth, was revealed in April.
"Ten
years ago, we knew of no extrasolar planets," said John Bally, an astronomer
at the University of Colorado in Boulder. "Now we're discovering planets
almost weekly."
"Extrasolar
planets are everywhere in the sky," said Sylvain Korzennik, a researcher
at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
In
addition to simply boosting the count of planets, new technologies are letting
scientists begin to analyze the chemical makeup of their finds.
Water
molecules have been spotted in the atmosphere of at least one new planet. The
fingerprints of elements such as carbon, oxygen, sodium, silicon and iron have
shown up.
So
far, none of the known exoplanets seems likely to harbor life. That is because
almost all the discoveries are gas giants, as big or bigger than Jupiter. Most
of them huddle close to their stars -- inside Mercury's orbit if they were in
Earth's solar system -- and are far too hot for liquid water, an essential for
life on Earth. Many orbit so rapidly that their years last only a few days.
Planet
hunters are confident that new telescopes soon will be able to identify smaller,
solid bodies in Earthlike orbits in the so-called habitable zone: close enough
-- but not too close -- to their stars to permit liquid water and perhaps life.
The
pace of discovery is bound to increase.
A
European planet-hunting satellite, named Corot, was launched in December and reported
its first discovery May 3.
In
early 2009, NASA is to launch a more powerful telescope, named Kepler, that will
monitor 100,000 stars in the northern sky for four years. Kepler will have "enough
precision to find Earth-size planets," said William Borucki, a space scientist
at NASA's Ames Research Laboratory in Mountain View, Calif.
Borucki
said he hoped to find 50 Earthlike planets and 500 objects twice as massive.
