New ‘super-earth’ discovered in the sun’s neighbourhood


A planet three times bigger than Earth orbits a star just six light-years away. Ben Lewis reports.


An unusually heliocentric illustration showing the proximity of Barnard's Star to the sun.

An unusually heliocentric illustration showing the proximity of Barnard's Star to the sun.

IEEC/Science-Wave - Guillem Ramisa

Astronomers have announced the discovery of a super-Earth in our relative neighbourhood.

The planet measures around 3.2 times the mass of Earth, and was discovered orbiting Barnard’s Star, fewer than six light-years from the sun. That makes it the second closest exoplanet to Earth, according to Ignasi Ribas from the Institute of Space Studies of Catalonia in Spain.

The planet, the description of which is published in the journal Nature, was discovered by same projects which have previously discovered the exoplanet Proxima b, orbiting our closest star Proxima Centauri.

A red dwarf that predates the solar system, Barnard’s Star is the closest solitary star to the sun. Its proximity to the solar system has made it a long-running candidate in the hunt for exoplanets, but previous searches have found none.

Analysing more than 20 years of data, Ribas found the planet orbiting its host at just 40% of the equivalent distance that the Earth orbits the sun – roughly the same distance out as Mercury.

That means it has a “year” of about 233 days. Even at such a close distance the planet would still have a dim existence, because Barnard’s Star emits far less energy than the sun.

This places the exoplanet close to the “snow line”, the region where volatile compounds such as water can condense into solid ice. The researchers write that this freezing, shadowy world could have a temperature of minus-170 degrees Celsius, probably thsu making it inhospitable for life as we know it.

“After a very careful analysis, we are 99% confident that the planet is there,” says Ribas. They haven’t, however, ruled out the possibility of at least one other planet further out from the star.

  1. https://www.nature.com/articles/s41586-018-0677-y
  2. https://www.eso.org/public/news/eso1629
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