*Tokyo: *Scientists have discovered 15 new planets – including one’super-Earth’ that could harbour liquid water – orbiting small, cool starsnear our solar system.
The stars, known as red dwarfs, are of interest for studies of planetaryformation and evolution, said the team led by Teruyuki Hirano from theTokyo Institute of Technology.
“Red dwarf systems, especially coolest red dwarfs, are just beginning to beinvestigated, so they are very exciting targets for future exoplanetresearch,” Mr Hirano said.
One of the brightest red dwarfs – K2-155 that is around 200 light yearsaway from Earth – has three transiting “super-Earths”, which are slightlybigger than our own planet.
Of those three “super-Earths”, the outermost planet, K2-155d, with a radius1.6 times that of Earth, could be within the host star’s habitable zone,the researchers noted in the study appeared in The Astronomical Journal.
The team found that K2-155d could potentially have liquid water on itssurface based on three-dimensional global climate simulations.
To reach this conclusion, the team sifted through data from NASA Keplerspacecraft’s second mission, K2, and follow-up observations usingground-based telescopes, including the Subaru Telescope in Hawaii and theNordic Optical Telescope (NOT) in Spain.
A more precise estimate of the radius and temperature of the K2-155 starwould be needed to conclude definitively whether K2-155d is habitable.
Achieving such precision would require further studies, for example, usinginterferometric techniques, the researchers said.
The researchers also investigated the relationship between planet radiusand metallicity of the host star.
“Large planets are only discovered around metal-rich stars and what wefound was consistent with our predictions. The few planets with a radiusabout three times that of Earth were found orbiting the most metal-rich reddwarfs,” Hirano noted.
With the planned launch of NASA’s Transiting Exoplanet Survey Satellite(TESS) in April this year, Mr Hirano is hopeful that even more planets willbe discovered.
“TESS is expected to find many candidate planets around bright stars closerto Earth,” he said. – Agencies