According to the team from the Tokyo Institute of Technology's Department of Earth and Planetary Scientists, the 15 exoplanets are orbiting red dwarf stars.
Common, relatively cool and potentially life-supporting, red dwarf stars are of particular interest to astronomers hunting down distant worlds.
According to simulations, it's even possible that the planet, known as K2-155d, might have liquid water on its surface, although the scientists involved in the study are quick to note that this is purely guesswork and that there's no indication yet as to what type of materials this world might be made of. Three super-Earths were found to be orbiting that bright red dwarf, but it was the outermost planet, K2-155d, that stood out as possibly being within K2-155's habitable zone.
The findings on K2-155d are based on data from the NASA Kepler spacecraft's second mission, K2, and follow-up observations from ground-based telescopes in Hawaii and Spain, among other places. The researchers will need a more precise estimate of the radius and temperature of K2-155, likely using interferometric techniques, to conclude definitively whether K2-155d is habitable. The stars these planets are orbiting are called red dwarfs.
Given that red dwarfs emit less light, the habitable zones covered by those stars are much smaller compared to the solar-type star that Earth is orbiting. Hirano also points out that red dwarf stars are just beginning to be investigated and are "exciting" targets for exoplanet research.
This is unedited, unformatted feed from the Press Trust of India wire.
As scientists noted, they were interested in celestial bodies revolving around stars that are not like our Sun and red dwarfs, which are small and boring stars with a bigger lifespan. It is expected that more planets will be discovered.
The planets were discovered using the transition method where planets give their presence away when they pass in front of a star, causing it to block out light which reaches Earth.
The studies were conducted as part of the KESPRINT collaboration, a group formed by the merger of KEST (Kepler Exoplanet Science Team) and ESPRINT (Equipo de Seguimiento de Planetas Rocosos Intepretando sus Transitos) in 2016. "TESS should find many candidate planets around bright stars closer to Earth", notes Teruyuki Hirano. Planets like Jupiter and Saturn are believed to have grown so large because their atmosphere had room to expand, and as such, it makes sense that a red dwarf might not provide the adequate environment for this process to take place. There seems to be a "gap" in the number of exoplanets with a radius between about 1.5 and 2 times that of Earth.
Nasa is planning on launching its Transiting Exoplanet Survey Satellite (TESS) in April this year, and it could open up new discoveries like this one. "This will greatly facilitate tracking observations, including the study of planetary atmospheres and determination of the precise orbit of planets".