A team of international scientists detected a rocky, super-Earth orbiting within the so-called "habitable zone of a cool M-type star about 40 light-years away.

The planet, described in a paper published in the journal Nature, is about 1.4 times the radius of the Earth and about 6.6 times its mass. The size and mass of the new planet, dubbed as LHS 1140b, highly suggests that it has a rocky composition.

"This is the most exciting exoplanet which I have seen in the last ten years" said study first author Jason Dittmann, from the Harvard-Smithsonian Centre for Astrophysics (CfA), in a press release. "It would be difficult to find a better objective for carrying out one of the most important searches in science: for evidence of life beyond the Earth".

The researchers detected LHS 1140b using the so-called transit technique. Transits occur when a planet orbiting a distant star comes between its host star and the Earth, cutting off a small portion of the star's light when viewed from Earth.

First detected in 2014 by the MEarth projects, the presence of LHS 1140b was later confirmed using data from MEarth-South, at the Interamerican Observatory of Cerro and the HARPS spectrograph on the 3.6m telescope at the La Silla Observatory of the European Southern Observatory. Both observatories are located in Chile.

LHS 1140b orbits around the M-type star known as LHS 1140 with a period of 25 days. M-type stars are the type of stars that have sizes and luminosities lesser than our Sun. Additionally, M-type stars are the most abundant stars in our Galaxy.

What makes the newly discovered planet interesting is that it orbits within the habitable zone, the region around the star that has the right temperature for water to exist in all different states: solid, liquid and gas.

The temperature and mass of LHS 1140b mean that it's possible to retain its own atmosphere. This makes the planet one of the most promising candidates for the detection and study of atmospheres and life beyond Earth.