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ESO's HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B
10.16.2012

See European Southern Observatory full press release at
http://www.eso.org/public/news/eso1241/

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.
Artist’s impression shows the planet orbiting the star Alpha Centauri B. Original artwork is in full press release - http://www.eso.org/public/news/eso1241/
Credit: ESO/L. Calçada/N. Risinger (skysurvey.org)

Excerpt: European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results [are] online in the journal Nature on 17 October 2012.
[http://www.eso.org/public/archives/releases/sciencepapers/eso1241/eso1241a.pdf]

Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System — only 4.3 light-years away. It is actually 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. Since the nineteenth century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

“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, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), 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...it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.

…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 orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet’s skies….

“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,” adds Stéphane Udry (Geneva Observatory), a co-author of the paper and member of the team, “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.”

“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….

Artist’s impression of the planet around Alpha Centauri B (Annotated)

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. Original artwork is in full press release - http://www.eso.org/public/news/eso1241/
Credit: ESO/L. Calçada/N. Risinger (skysurvey.org)



See also: 2012-10-22. Out There: Discovery Rekindles Wish for a Journey to the Stars | by Dennis Overbye, New York Times. Excerpt: The discovery last week of an Earth-like planet circling Alpha Centauri B "set off an epidemic of daydreaming among the astronomical and sci-fi set," including Sara Seager, an MIT astronomer, who repeated a call made last year by Berkeley astronomer Geoff Marcy that "we should drop everything and send a probe there.” "But if astronomers have learned anything over the last few years from devices like the Kepler satellite, it is that small planets come in packs. There is plenty of room in the system for more planets, habitable ones." Read the full article: http://www.nytimes.com/2012/10/23/science/space/discovery-rekindles-wish-for-a-journey-to-the-stars.html?scp=8&sq=Berkeley&st=nyt

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