The Alpha Centauri binary system (double star) has a little friend. Researchers have finally made the discovery that an Earth-like planet orbits Alpha Centauri B, the most brilliant object in the sky. A cozy 4.3 light years away, it marks the end of hundreds of years of speculation about planets orbiting Alpha Centauri. The discovery was made by a team lead by Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper which is now available in the scientific journal Nature.
“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,” said Dumusque. ”It’s an extraordinary discovery and it has pushed our technique to the limit!”
According to the paper, Dumusque and team found the planet by observing tiny oscillations in Alpha Centauri B, created by the planet’s gravitation pull. The perturbations are minuscule to the human eye—51 centimetres per second (1.8 km/hour), to be exact. At six million kilometers from Alpha Centauri B, it’s orbit is approximately that of Mercury’s in relation to our Sun.
As to whether there is life on the planet, it’s not likely. But there may be other planets to be discovered by researchers down the road.
“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.”