Although it is now 11 light-years from Earth, Ross 128 is moving towards us and is expected to become our nearest stellar neighbour in just 79 000 years-a blink of the eye in cosmic terms.
The new planet was discovered by an worldwide team of astronomers using the European Southern Observatory's (ESO) High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in the high desert of Chile.
The astronomers don't yet know whether Ross 128 b is in the habitable zone of its star, but it's likely, given what they understand about red dwarfs and the planets that orbit them.
Ross 128 is the "quietest" nearby star to host such a temperate exoplanet and its newly discovered companion - which orbits its host star in only 9.9 days - is the second-closest temperate planet to be detected after the discovery of Proxima b past year.
Ross 128 b is not the closest Earth-like world to us.
The chance to analyse these worlds more will come when the European Southern Observatory opens the European Extremely Large Telescope (E-ELT) in 2024. That distinction goes to Proxima Centauri b, which was discovered in 2016, and is just 4.24 light years away.
Although discoveries of this type are relatively uncommon at present, it is likely that temperate exoplanets such as these will be found in greater number with advancing technology. Ross 128 appears at the centre of the picture.
It will allow astronomers to collect the light from Ross 128 b and analyse it for biological gases such as oxygen.
The planet also orbits some 20 times closer to its star compared to Earth and our Sun.
No other star system has ever been found to contain so many Earth-sized and rocky planets of the kind thought to be necessary to contain aliens. If the planet is too close to the star, its water would evaporate; too far away and the water would freeze into ice.
This image shows the sky around the red dwarf star Ross 128 in the constellation of Virgo. In addition, it has a surface temperature from -60°C to 20°C.
Lead author Doctor Xavier Bonfils, said that many red dwarf stars, including Proxima Centauri, are subject to flares that occasionally bathe their orbiting planets in deadly ultraviolet and X-ray radiation. Ross 128 b could change this, because the planet and its star are moving toward us.
"Stellar activity is probably the highest concern regarding the emergence of life, and even the survival of an atmosphere", the study says.
Astronomers have spotted a roughly Earth-mass world circling the small, dim star Ross 128, which lies just 11 light-years from the sun. For that reason, the scientists refer to Ross 128 b as "the best temperate planet known to date". Considering the oldest human remains are thought to be hundreds of thousands or even millions of years old, it's not insane to think our species could still be roaming the Earth when Ross 128 b becomes the closest exoplanet to our home world.