Published: Tue, March 13, 2018
Research | By Jody Lindsey

Scientists discover 15 new planets orbiting red dwarf stars

Scientists discover 15 new planets orbiting red dwarf stars

Hirano further commented on the finding that planets that orbit red dwarfs have a similar radius gap to planets orbiting solar-type stars, saying that his team's discovery was "unique", and that astronomers are now trying to figure out the reason behind the radius gap.

New research has confirmed the presence of 15 exoplanets orbiting smaller, cooler red dwarf stars. The findings the scientists have made are based on data from the Kepler spacecraft's second mission and follow-up observations from ground-based telescopes including the Subaru Telescope in Hawaii and Nordic Optical Telescope in Spain.

Three super-Earths slightly bigger than our own planet were found transiting one of the brightest red dwarfs, K2-155, which is located around 200 light years away from Earth. The space agency also hopes to document over 1,500 transiting exoplanet candidates with TESS, including about 500 which could be classified as Earth-sized or super-Earth planets. It is the home to three planets, the farthest of which, K2-155d, looks habitable and, according to the scientists, is similar in its climate and hydrological conditions to the Earth.

One of the primary outcomes of the new research highlighted that the planets surrounding red dwarf stars may have exceptionally similar characteristics to planets orbiting solar system stars.

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Astronomers will have to calculate K2-155d's radius and temperature to see if it really is habitable. Teruyuki Hirano who is a researcher at the Department of Earth and Planetary Sciences at Tokyo Institute of Technology stated that planets which revolve around red dwarfs are usually smaller compared to the one revolving around solar-type stars. Hirano expresses both excitement and restraint, as he says: "In our simulations, the atmosphere and the composition of the planet were assumed to be Earth-like, and there's no guarantee that this is the case". Hirano also points out that red dwarf stars are just beginning to be investigated and are "exciting" targets for exoplanet research. The planets orbiting red dwarfs are usually tidally locked to the star, meaning that only one side of the planet is lightened by the star and the other side is in darkness. According to Hirano, the gap is likely due to the lack of large planets in the proximity of host stars, which is caused by photoevaporation, which can strip away the envelop of the planetary atmosphere. It's been observed that, where large planets do form around cool dwarf stars, the stars in question typically have a higher metal count.

Going forward, Hirano is optimistic that NASA's Transiting Exoplanet Survey Satellite (TESS) would yield more information on potentially habitable super-Earths such as K2-155d.

The red dwarf system is an interesting premise that the scientists need to investigate further. The results show a "radius gap", or a dip in the number of stars with a radius between 1.5-2.0 times that of Earth. "This will greatly facilitate tracking observations, including the study of planetary atmospheres and determination of the precise orbit of planets".

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