March 13, 2006

Icy “super-Earth” found around faraway star

WASHINGTON (Reuters) - A cold, heavy "super-Earth" has been
found orbiting a distant star, using a method that holds
promise for detecting faraway planets that closely resemble our
own, astronomers said on Monday.

The planet weighs 13 times as much as Earth and is orbiting
a star about 9,000 light-years away. But instead of circling
close to its star, as Earth does, this "super-Earth" is about
as distant from its star as Jupiter and Saturn are from the

An international team of scientists figured the new planet
probably has a temperature of minus 330 degrees F (minus 201
C), making it one of the coldest planets detected outside our
solar system.

The discovery is billed as a super-Earth because it is
thought to be a rocky, terrestrial planet like Earth, even
though it is much more massive.

The planet was detected by astronomers using a project
called OGLE -- short for Optical Gravitational Lensing
Experiment -- which looks for changes in light coming from
distant stars.

If another star passes between the faraway star and a
telescope on Earth, the gravity of the intervening star acts
like a lens and magnifies the incoming light.

When a planet is orbiting the closer star, the planet's
gravity can add its own distinctive signature to the light.

This phenomenon is known as gravitational microlensing, and
it has the potential to detect less massive planets than other
methods of searching for planets around other stars.


The OGLE project detected the microlensing event in April;
36 astronomers working with OGLE found the signs of a planet,
9,000 light-years away in the direction of the Milky Way's
central galactic bulge.

A light-year is about 6 trillion miles, the distance light
travels in a year.

Andrew Gould, an Ohio State University professor who heads
the planet-hunting group MicroFUN -- short for Microlensing
Follow-Up Network -- said this discovery has two implications.

"First, this icy super-Earth dominates the region around
its star that in our solar system is populated by the gas-giant
planets, Jupiter and Saturn," Gould said in a statement. "We've
never seen a system like this before, because we've never had
the means to find them.

"And second," he said, "these icy super-Earths are pretty
common. Roughly 35 percent of all stars have them."

In the last decade, scientists have detected some 170
so-called extrasolar planets, using a variety of techniques.
The vast majority are gas giant planets like Jupiter which are
hostile to life as it is known on Earth.

In January, a planet about five-and-a-half times Earth's
mass circling a star near the center of the Milky Way was
detected using gravitational microlensing.