As names go, Ross-128b belies the exciting potential of this remote, Earth-sized planet to harbor life. Perched in orbit around the dimly-glowing Class M red dwarf star called Ross 128, which is about one fifth of the size of the Sun, Ross 128b has taken researchers at the European Southern Observatory (ESO) more than a decade to detect. 5 Xavier Bonfils and his colleagues, who have published the findings in the journal Astronomy and Astrophysics, used an instrument called HARPS – short for High Accuracy Radial velocity Planet Searcher – at the La Silla Observatory, in Chile, to spot regular tiny dips in the intensity of the light reaching the Earth from the Ross 128 star.

These dips, which occurred roughly every 10 days, correspond to the planet passing in front of 10 the parent star, blocking the path of some of its light and making it momentarily dimmer. The orbiting planet also pulls on the host star as it moves around it, producing a warping effect that slightly alters the color of the light reaching us. And because the researchers know how big the star is, this color shift can be used to calculate the size and mass of the planet.

Liquid water could well exist under these conditions, because the planet is sitting either just 15 inside, or on the cusp of what is dubbed the habitable zone. This is the “Goldilocks” section of space around a star where the temperature is just right to sustain life processes. The observations for Ross 128b suggest average surface temperatures of relatively comfortable range, somewhere between -60°C and +20°C. Whether there is water there, and the prospect for finding life too, will depend heavily upon the 20 existence of an atmosphere, which the researchers have not been able to measure yet. Before they do, they must to decide which molecules to look for as hallmarks of life itself.