Nearby Planet Found Circling Ancient Star May Have Water

One of the two newly discovered planets, circling an ancient star that is near to our own Sun, may have water on its surface, a new finding suggests.

A team of international astronomers in collaboration with Carnegie scientists has found new planets orbiting an ancient star,  Kapteny's Star, that was discovered at the end of the 19^th century.  Two of the planets orbiting the star that is a third of the mass of the Sun, are located at the right distance that might allow liquid water to exist on the surface, a key ingredient to support life.

Kapteyn's star is known to be the second fastest moving star in the sky and is a part of the Galatic halo. This red dwarf can be easily visible with an amateur telescope in the southern constellation of Pictor.

Using the new data from the HARPS spectrometer at the European Southern Observatory's La Silla observatory, the Planet Finding Spectrometer and the HIRES Spectrometer, the astronomers measured the tiny periodic changes in the motion of the star. With the help of the Doppler Effect, the researchers inferred some of the properties of the two planets which include their masses as well as the orbital periods.

"We were surprised to find planets orbiting Kapteyn's star. Previous data showed some irregular motion so we were looking for very short period planets when the new signals showed up loud and clear," explains lead author Dr. Guillem Anglada-Escude, from the Queen Mary University of London.

The astronomers believe that Kapteyn b that is five times the mass of Earth and orbits the star every 48 hours might hold water suggesting the planet is warm enough to hold water on its surface.

The second planet, Kapteyn c,  is much more massive compared to Kapteyn b. It is too cold to support liquid water and has an orbital period of 121 days.

Currently the researchers have learnt just a few properties of the planets that include mass, orbital periods and distance from the host star. The presence of water will be verified by measuring the planet's atmosphere using instruments that are currently under development.

"Finding a stable planetary system with a potentially habitable planet orbiting one of the very nearest stars in the sky is mind blowing. This is one more piece of evidence that nearly all stars have planets, and that potentially habitable planets in our Galaxy are as common as grains of sand on a beach," said Pamela Arriagada, the second author, and a Carnegie postdoctoral researcher.

This finding is interesting as it was believed that Kapteyn's star was born in a dwarf galaxy and was destroyed and sucked by the Milky Way. But this galactic cannibalization puts the star on a new path making it a part of the Milky Way's halo.