A research team led by Teruyuki Hirano of the Department of Earth Sciences and Planets of the Tokyo Institute of Technology validated a few days ago the discovery of 15 new exoplanets in orbit around red dwarfs.
The results, published as two articles in The Astronomical Journal, are based on new data collected by Kepler’s second K2 mission. Follow-up observations were then made on the ground with the Subaru telescope in Hawaii, and the Nordic Optical Telescope (NOT) in Spain. Among these stars, one of the brightest — K2-155 — is about 200 light-years away from Earth. There would be around this red dwarf three super-earths in orbit, slightly larger than our own planet. Of these three super-Earths, the outermost planet, K2-155d, has a radius of 1.6 times that of the Earth and could be in the habitable zone of its host star.
Based on three-dimensional climate simulations, the researchers also explain that K2-155d could potentially have liquid water on the surface. “In our simulations, the atmosphere and the composition of the planet are supposed to be similar to Earth, but there is no guarantee that this is the case,” say the scientists.
A more accurate estimate of the radius and temperature of star K2-155 will be needed to definitively conclude whether K2-155d is habitable or not.
The red dwarfs have for long been neglected by extraterrestrial life hunters, who thought that the planets in orbit around did not offer the conditions favorable to the appearance of life. Yet, these stars, among the oldest and the darkest in the universe, are numerous. They prove to be far more numerous than the stars of the size of our Sun – nearly 75% of the stars of our Galaxy. This is why astronomers are leaning more and more towards them.
Astronomers will soon be able to rely on the satellite TESS, whose launch is scheduled for next April. It is expected that more planets will be discovered. “TESS should find many candidate planets around bright stars closer to Earth,” notes Teruyuki Hirano. “This will greatly facilitate tracking observations, including the study of planetary atmospheres and determination of the precise orbit of planets.”