Found! Potentially Earth-Like Planet at Proxima Centauri is Closest Ever

Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System.
Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System.

The star closest to the sun hosts a planet that may be very much like Earth, a new study reports.

Astronomers have discovered a roughly Earth-size alien world around Proxima Centauri, which lies just 4.2 light-years from our own solar system. What’s even more exciting, study team members said, is that the planet, known as Proxima b, circles in the star’s “habitable zone” — the range of distances at which liquid water could be stable on a world’s surface.

“We hope these findings inspire future generations to keep looking beyond the stars,” lead author Guillem Anglada-Escude, a physics and astronomy lecturer at Queen Mary University of London, said in a statement.”The search for life on Proxima b comes next.” [In Pictures: The Discovery of Planet Proxima b]

A Long Search

The discovery of Proxima b was a long time in the making.

Astronomers have been hunting intensively for planets around Proxima Centauri for more 15 years, using instruments such as the Ultraviolet and Visual Echelle Spectrograph (UVES) and the High Accuracy Radial velocity Planet Searcher (HARPS), both of which are installed on telescopes run by the European Southern Observatory in Chile.

UVES, HARPS and other instruments like them allow researchers to detect the slight wobbles in a star’s movement caused by the gravitational tugs of orbiting planets.

Astronomers found hints of such a wobble back in 2013, but the signal was not convincing, Anglada-Escude said. So he and a number of other researchers launched a campaign to ferret out the planet. They called this effort the Pale Red Dot — a nod to Carl Sagan’s famous description of Earth as a “pale blue dot,” and the fact that Proxima Centauri is a small, dim star known as a red dwarf.

The Pale Red Dot team focused HARPS on Proxima Centauri every night from Jan. 19, 2016, through March 31 of this year. After they combined this new data with UVES observations from 2000 through 2008 and HARPS observations from 2005 through early 2014, the signal of a possible planet came through loud and clear.

Then, after analyzing observations of the star’s brightness made by several other telescopes, Anglada-Escude and his colleagues ruled out the possibility that this signal could be caused by the variable activity of Proxima Centauri.


“The conclusion: We have found a planet around Proxima Centauri,” Anglada-Escude said Tuesday (Aug. 23) during a news conference.


How did Proxima b remain undetected for so long, in an era when astronomers are finding exoplanets thousands of light-years from Earth?

“The uneven and sparse sampling, combined with the longer term variability of the star, seem to be the reasons why the signal could not be unambiguously confirmed with pre-2016 data, rather than the total amount of data accumulated,” the researchers wrote in the new study, which was published online today (Aug. 24) in the journal Nature.

The news confirms rumors first reported earlier this month by German magazine Der Spiegel.