New super-Earths found close to home

Astronomers report detecting two, maybe even three, super-Earth exoplanets orbiting the brightest red dwarf star in the sky.

More importantly, they say GJ 887, which has roughly half the mass of our Sun, is just 11 light-years away, making this one of the closest multi-planet systems to our Solar System – and offering an opportunity to study exoplanet atmospheres.

Super-Earths are more massive than the Earth but substantially less massive than Uranus or Neptune.

“We now know of thousands of planets of super-Earth-mass or smaller, but most of those planets orbit distant and faint stars,” says Chris Tinney from Australia’s University of NSW, a co-author of a paper in the journal Science.

“Planets orbiting nearby stars are key for searches with future telescopes for both exoplanetary atmospheres, and eventually evidence for life.”

The research team, which was led by Sandra Jeffers from Germany’s University of Göttingen, used a technique known as Doppler wobble to observe GJ 887 each night for three months, then combined its data with archival measurements of the star spanning nearly 20 years.

The astronomers detected the presence of two super-Earth sized planets, tightly circling the nearby red dwarf with orbital periods of 9.3 and 21.8 days. They also found evidence for a possible third farther out, with an orbital period of approximately 50 days.

They suggest that the confirmed planets are likely too hot to maintain liquid water on their surfaces. However, the more distant location of the unconfirmed third planet may place it within GJ 887’s so-called “habitable zone”.

GJ 887 is less active than other red dwarfs, so the newly discovered worlds may be spared from harmful solar flares common to that type of star.

“If someone had to live around a red dwarf, they would want to choose a quieter star like GJ 887,” writes Melvyn Davies, from Sweden’s University in Lund, in a related Perspective article in the journal.

“If further observations confirm the presence of the third planet in the habitable zone, then GJ 887 could become one of the most studied planetary systems in the solar neighbourhood.”