Astronomers discovered the planet using the European Southern Observatory's High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile.
The facility can take measurements of radial velocities with the highest accuracy currently available – to the order of 1 metre/second.
This allows HARPS to identify minor 'wobbles' in a star's movement, induced by the gravitational tugs of orbiting planets.
Dr Nicola Astudillo-Defru, of the University of Geneva in Switzerland, said: 'This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques.
'Only HARPS has demonstrated such a precision and it remains the best planet hunter of its kind, 15 years after it began operations.'
Dr Xavier Bonfils, of Université Grenoble in France, named the HARPS programme 'the shortcut to happiness' as it is easier to detect small cool siblings of Earth around these stars, than around stars more similar to the sun..
Astronomers are now detecting more and more temperate exoplanets, and the next stage will be to study their atmospheres, composition and chemistry in more detail.
Vitally, the detection of biomarkers such as oxygen in the very closest exoplanet atmospheres will be a huge next step, which ESO's Extremely Large Telescope (ELT) is in prime position to take.
Dr Bonfils added: 'New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation.
'In particular, NIRPS, the infrared arm of HARPS, will boost our efficiency in observing red dwarfs, which emit most of their radiation in the infrared.
'And then, the ELT will provide the opportunity to observe and characterise a large fraction of these planets.'
Astronomers working with HARPS found that the red dwarf star Ross 128 is orbited by a low-mass 'exoplanet' every 9.9 days.
With the data from HARPS, the team found that Ross 128b orbits 20 times closer than the Earth orbits the sun.
But, despite the proximity, Ross 128b receives only 1.38 times more irradiation than the Earth.
As a result, Ross 128 b's equilibrium temperature is estimated to lie between -60 and 20°C (-76° to 68°F), thanks to the cool and faint nature of its small red dwarf host star, which has just over half the surface temperature of the sun.
While the scientists involved in the discovery consider Ross 128b to be a temperate planet, uncertainty remains as to whether the planet lies inside, outside, or on the cusp of the habitable zone, where liquid water may exist on a planet's surface.
Source : http://www.dailymail.co.uk/sciencetech/fb-5946559/HOW-ROS-128-HOST-LIFE.html449