Earth-size planets spotted around distant star
24 Dec Yahoo News
Scientists have found two Earth-sized planets orbiting a star outside
the solar system, an encouraging sign for prospects of finding life
elsewhere.
The discovery shows that such planets exist and that they can be
detected by the Kepler spacecraft, said Francois Fressin of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
They’re the smallest planets found so far that orbit a star
resembling our sun. Scientists are seeking Earth-sized planets as
potential homes for extraterrestrial life, said Fressin, who reports the
new findings in a paper published online Tuesday by the journal Nature.
One planet’s diameter is only 3 percent larger than Earth’s, while
the other’s diameter is about nine-tenths that of Earth. They appear to
be rocky, like our planet. But they are too hot to contain life as we
know it, with calculated temperatures of about 1,400 degrees and 800
degrees Fahrenheit, he said.
Any life found on another plant may not be intelligent; it could be
bacteria or mold or some completely unknown form. Since it was launched
in 2009, NASA’s planet-hunting Kepler telescope has found evidence of
dozens of possible Earth-sized planets. But Fressin’s report is the
first to provide confirmation, said Alan Boss of the Carnegie
Institution for Science in Washington. He’s a member of the Kepler
science team but not an author of the paper.
The researchers ruled out a possible alternative explanation for the
signals that initially indicated the planets were orbiting the star
Kepler-20. The star is 950 light-years from Earth in the direction of
the constellation Lyra. The planets, called Kepler-20e and Kepler-20f,
are part of a five-planet system around the star, and their location
challenges current understanding of how planets form, scientists said.
In our own solar system, the small rocky planets are closest to the
sun, while gaseous giants are on the periphery. But the five-planet
system has no such dividing line; big and small planets alternate as one
moves away from the star.
That’s “crazy,” and unexplained by current understanding of how
planets form around stars, said study co-author and Harvard scientist
David Charbonneau.
Earlier this month, scientists said they’d found a planet around
another distant star with a life-friendly surface temperature of about
72 degrees. But it was too big to suggest life on its surface.
At 2.4 times the size of Earth, it could be more like the
gas-and-liquid Neptune with only a rocky core and mostly ocean,
scientists said. |