Old data reveals Super-Earth lurking in a nearby star's habitable zone

UPR Arecibo

A reanalysis of old data obtained by an Earth-based observatory has found what seems to be the signal of a large planet, somewhere between the mass of Earth and Neptune, orbiting a dwarf star about 42 light years from Earth. It's part of a crowded system of six planets, but appears to be the only one of them that's in the host star's habitable zone. And, according to the people who have identified it, the planet should be close enough to Earth to be imaged directly by some of the observatories currently in the planning stages.

The star in question is HD 40307, which is only about three-quarters the mass of the Sun, and quite a bit dimmer. The star has been targeted for observations using the HARPS, the same instrument that recently spotted the signal of an exoplanet in the Alpha Centauri system. The instrument looks for periodic changes in the light emitted by the star. These arise from Doppler shifts caused by its orbiting planets, which periodically pull the star in different directions.

The HARPS team had already analyzed data from HD 40307, and determined that there were three planets apparent in the data obtained by the instrument. But now, an international team of researchers has gone back and reanalyzed the data using a number of different methods. Their work suggests there are at least six planets in the system.

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