[meteorite-list] FIRST TERRESTIAL (EARTH-LIKE) EXTRA-SOLAR PLANET FOUND

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu Jan 26 16:45:05 2006
Message-ID: <004701c622c1$ad6b22f0$727cd745_at_ATARIENGINE>

Hi,

    Just announced today, the discovery
of a 5.5 Earth-mass planet, 2.5 AU from
its dim parent star, 28,000 light years
away, using gravitational lensing.
    This is too small to be a Jovian or
gas giant, so it has to be a rocky body.
    Or, since its probable temperature
is -220 degreed C, rock and ice is more
like it.
    Here's the URL and the text of the
article in Nature:

Sterling K. Webb
------------------------------------------

http://www.nature.com/news/2006/060123/full/060123-5.htm

Found: one Earth-like planet
Astronomers use gravity lensing to spot homely planets.
by Mark Peplow

Astronomers say they have found the most Earth-like planet yet outside our
Solar System. At just 5.5 times the mass of Earth it is one of the smallest
extrasolar planets ever found, and orbits its star at a distance comparable
to that of habitable worlds.

Similarly sized extrasolar planets have been found before. But the method
used to detect them meant we could see smallish planets only when they were
very close to their suns, and such bodies are battered by scorching
radiation.

Planet OGLE-2005-BLG-390Lb looks much more like home. It lies about 390
million kilometres from its star: if it were inside our Solar System, the
planet would sit between Mars and Jupiter.

It takes ten years for the planet to orbit its parent star, a
common-or-garden red dwarf that lies about 28,000 light years from Earth,
close to the centre of our Galaxy.

But sadly this Earth-like body probably isn't crawling with life. Its dwarf
star is so dim that the surface temperature of this planet is thought to be
about - 220 ?C.

"The search for a second Earth is the driving force behind our research,"
says Daniel Kubas at the European Southern Observatory in Santiago de Chile,
Chile, part of the team that made the discovery. They are optimistic that
the clever method they used to spot the planet could soon uncover an alien
twin to our own world.

Wobbly stars

More than 170 planets have been discovered outside our Solar System.
Astronomers usually detect them by watching how they make their parent star
wiggle, a technique known as the Doppler method. This is ideal if you are
looking for massive planets orbiting very close to their star, which induce
a lot of wobble.

But there is no way this can be used to find small, blue-green planets
approximately 150 million kilometres from a yellow sun. It is simply not
sensitive enough, says Didier Queloz, an astronomer from Geneva Observatory
in Switzerland who was part of the team that found the first extrasolar
planet, just 11 years ago1.

The new sighting relies on an effect called gravitational lensing, where a
massive object such as a star warps space so that it behaves like a lens.
This means that it bends and slightly magnifies light from a more distant
star before it reaches our telescopes. Adding a planet to the mix modifies
the lensing effect by a tiny amount, just enough to work out its mass and
orbit.

"Microlensing is the fastest way to find small, cool planets, down to the
mass of the Earth," says Keith Horne, one of the planet's discoverers and an
astronomer from the University of St Andrews, UK.

Spot the difference

The planet was found by a consortium of 73 astronomers from 12 different
countries. Its star was first spotted by scientists working on the Optical
Gravitational Lensing Experiment (OGLE), before the planet itself was
noticed by astronomer Pascal Fouqu?.

OGLE-2005-BLG-390Lb is only the third planet found using the microlensing
technique so far, but astronomers expect to spot many more. "The other two
microlensing planets have masses of a few times that of Jupiter, but the
discovery of a five-Earth-mass planet is a strong hint that these objects
are very common," says Jean-Philippe Beaulieu of the Astrophysics Institute
of Paris. Beaulieu is lead author of the paper describing the find in this
week's Nature.
Received on Thu 26 Jan 2006 04:44:24 PM PST