Scientists used
the newly commissioned Gemini Planet Imager, which is mounted on
top of a telescope in Chile, to find the planet, known as 51
Eridani b. It circles a very young sun-like star that is located
about 96 light years from Earth.
The planet, which is about double the size of Jupiter, is
positioned a bit farther away from its parent star than Saturn
orbits the sun. 51 Eridani b is one of the smallest planets
beyond the solar system to be directly imaged.
Still radiating heat from its formation less than 20 million
years ago, or about 40 million years after dinosaurs became
extinct, 51 Eridani b is glowing in infrared light, which is how
the telescope saw it.
"51 Eri b provides an opportunity to study in detail a planet
that is still influenced by its formation initial conditions,"
Stanford University astronomer Bruce Macintosh and colleagues
wrote in this week's issue of the journal Science.
Follow-up analysis revealed that the planet's atmosphere, like
Jupiter's, is dominated by methane. The discovery provides an
important clue for scientists trying to figure out how these
types of gas-giant planets form and evolve.
"51 Eri b is the first young planet that probably looks like
Jupiter did billions of years ago, making it currently our most
important cornerpiece of the planet-formation jigsaw puzzle,"
University of Arizona planetary scientist Travis Barman said in
a statement.
Astronomers have only been able to directly see a handful of
planets beyond the solar system and nearly all of those have
been five to 13 times as massive as Jupiter.
Other telescopes, like NASA's Kepler observatory, look for
planets indirectly. Kepler, for example, looked for slight dips
in the amount of light coming from target stars, a possible clue
that an orbiting planet was crossing the face of its parent
star.
Another method is to look for wobbles in starlight that may be
caused by the slight gravitational tugs of circling planets.
(Reporting by Irene Klotz. Editing by David Adams and Alan
Crosby)
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