Earth-Sized Planet Discovered in Alpha Centauri Star System, 4.3 Light-Years Away

Posted on October 17, 2012

Planet Orbiting Alpha Centauri B

European astronomers have announced the discovery of a planet with a mass about the same as the Earth orbiting a star in the Alpha Centauri system, the nearest star system to Earth. The triple star system is about 4.3 light-years away.

The planet was discovered using ESO's HARPS instrument. The instrument detected tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet. An artist's impression of the planet around Alpha Centauri B is pictured above. You can see a larger version of the image here.

Here is a fly-through of the Alpha Centauri system from the ESO Observatory. Take a look:

Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper to be published in Nature, said in the announcement, "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. It's an extraordinary discovery and it has pushed our technique to the limit!"

The planet orbits about six million kilometres away from Alpha Centauri B. It is closer to Alpha Centauri B than Mercury is to our Sun, so the surface of the planet is likely to be extremely hot - too hot for life as we know it.

Stephane Udry (Geneva Observatory), a co-author of the paper and member of the team, said in the release, "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, 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."

A story discusses the possibility of sending a probe if a potentially habitable planet is found orbiting Alpha Centauri B. says it is a possible target of the 100 Year Starship initiative. EarthSky also has an interesting article about how long it would take to get to Alpha Centauri. It is still an insanely long journey with our current space travel technology, but it is amazing discoveries like this that will fuel the passion for space travel and lead to breakthroughs that get us there faster than we envision possible today.

This video shows an imaginary journey from Earth to the Alpha Centauri system. Take a look:

Photo: ESO/L. Calcada

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