Astronomers discover earth-sized exoplanet just 4.3 light-years away

17 Oct 2012

Artist's impression showing the newly discovered planet orbiting the star Alpha Centauri B, a member of the triple star system Alpha Centauri that is the closest to earth. Image via ESO/L. Calçada/N. Risinger

Astronomers in Europe are claiming to have found the nearest planet outside of our solar system at just 4.3 light-years away. The exoplanet, which has a similar mass to Earth, is apparently the lightest exoplanet ever discovered around a star like the sun.

The astronomers discovered the planet orbiting a star in the closest stellar system to Earth, Alpha Centauri. The nearest stellar system to our own solar system, Alpha Centauri is a triple star and consists of two stars similar to the sun that orbit close to each other as well as a distant third star known as Proxima Centauri.

The astronomers said they detected the exoplanet using a 3.6-metre telescope at the European Southern Observatory’s (ESO) La Silla Observatory in Chile.

Their findings have been published in Nature this week.

According to the scientists, astronomers have been speculating since the 19th century that planets orbit around these stars in Alpha Centauri, but their searches have 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,” said the lead author of the paper Xavier Dumusque from Geneva Observatory in Switzerland and the Centro de Astrofisica da Universidade do Porto in Portugal.

The astronomers working with ESO said they found 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.

Based on their findings, it seems the newly discovered planet has a mass that is a little more than Earth’s mass. It orbits around 6m kilometres away from Alpha Centauri B. This orbit is much closer than Mercury is to the sun in our own solar system.

The astronomers said the next challenge is to detect and characterise a planet of mass similar to Earth that is orbiting in the habitable zone around another star.

“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,” said Stéphane Udry from Geneva Observatory and a co-author of the paper.

He said the planet could be just one planet in a system of several planets.

Carmel Doyle was a long-time reporter with Silicon Republic