MessageToEagle.com - European astronomers have discovered an intriguing planet with about the mass of the Earth
orbiting a star in the Alpha Centauri system, one of the brightest stars in the southern skies and located only 4.3
light-years away from Earth.
The planet is the lightest exoplanet ever found around a star similar to our Sun.
Alpha Centauri is a triple star - a system consisting of two stars similar to the Sun orbiting close to each other,
designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri.
Click on image to enlarge
This artist’s impression shows the planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Alpha Centauri B is the most brilliant object in the sky and the other dazzling object is Alpha Centauri A. Our own Sun is visible to the upper right. The tiny signal of the planet was found with the HARPS spectrograph on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile.
Credit: ESO/L. Calçada/N. Risinger (skysurvey.org)
"Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real,
signal from a planet orbiting Alpha Centauri B every 3.2 days," says Xavier Dumusque (Geneva Observatory, lead author of the paper.
"It's an extraordinary discovery and it has pushed our technique to the limit!"
The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created
by the gravitational pull of the orbiting planet.
Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with
a mass of a little more than that of the Earth, is orbiting about six million kilometres away from the star, much
closer than Mercury is to the Sun in the Solar System.
The first exoplanet around a Sun-like star was found by the same team back in 1995 and since then there have been
more than 800 confirmed discoveries, but most are much bigger than the Earth, and many are as big as Jupiter.
"This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to
its star and it must be much too hot for life as we know it," Stéphane Udry, a co-author of the paper said.
"But it may well be just one planet in a system of several.
Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems," Udry added.
"This result represents a major step towards the detection of a twin Earth in the immediate vicinity of the Sun. We live
in exciting times!" concludes Xavier Dumusque.
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