An international team of astronomers led by Guillem Anglada-Escude of the Queen Mary University, London, announced that they have found two planets that orbit the Kapteyn’s star, only 13 light years from Earth. In particular, the planet Kapteyn b is interesting because it is a super-Earth, meaning a rocky planet with a mass about five times the Earth, where liquid water could exist, one of the essential requirements to host life as we know it.

Kapteyn’s star was discovered only in 1898 by the Dutch astronomer Jacobus Kapteyn because it’s a class sdM1 red subdwarf, too small to be seen with the naked eye. It’s a halo star which orbits around the center of the Milky Way in a highly elliptical orbit.

There are several interesting facts about Kapteyn’s star. It, along with the Omega Centauri cluster it belongs to, is probably what remains of a dwarf galaxy that in the past merged with the Milky Way. It’s a very old star, about 11.5 billion years old.

The astronomers used the HARPS (High Accuracy Radial Velocity Planet Searcher) spectrometer installed on ESO’s telescope at La Silla Observatory in Chile to detect Kapteyn’s star’s planets. They also analyzed data from two other spectrometers: HIRES (High Resolution Echelle Spectrometer) at Keck Observatory and PFS at Magellan/Las Campanas Observatory.

The planet Kapteyn b orbits its star in just 48 days but if the atmosphere was similar to that of the Earth it would be colder than it because its star is very small. It’s possible that there is liquid water and if that’s the case it had plenty of time to develop life forms of the type we know.

The planet Kapteyn c orbits its star in 121 days but astronomers think it’s too cold to host water in the liquid state. This planet is another super-Earth even more massive that the other one in the system.

The observations of Kapteyn’s star’s system will continue to try to detect other data that would allow to understand what kind of atmosphere its planets have. If Kapteyn b turns out to be really potentially habitable, it would be further evidence that even very small stars but also very common need to be analyzed to look for alien life forms.

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