Scientists from the Tokyo Institute of Technology have discovered 15 new planets orbiting small, cool dwarf stars near our solar system, including one planet that may be habitable.
Their findings, recently published as two papers in The Astronomical Journal, are based on data from NASA Kepler spacecraft's second mission (K2) and other follow-up observations from the Subaru Telescope in Hawaii and Spain's Nordic Optical Telescope.
Through their analysis, the team confirmed the existence of the 15 exoplanets orbiting the K2-155 red dwarf star, including three super-Earths — planets that are “somewhat larger cousins” of Earth, but smaller than Neptune.
Based on global climate simulations, the researchers also discovered that one of the three super-Earths (K2-155d) could hold liquid water on its surface, making it potentially habitable. K2-155d had a radius that is 1.6 times larger than that of Earth.
But, lead researcher Teruyuki Hirano said in a news release, "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."
Unlike the solar-type star in Earth's solar system, habitable zones for red dwarf planets are typically much smaller and the planets orbiting the stars are much closer to the stars themselves, Tech Times reported.
This means that one side of the planet is “tidally locked” to the star, leading to potentially erratic storms that could deem the area unlivable.
To determine whether the planet truly is habitable, Hirano said more precise estimates of the radius and temperature of the K2-155 red dwarf star are necessary and would require further research.
It’s important to note that the number of planets around red dwarfs is much smaller than the number around solar-type stars,” Hirano added. “Red dwarf systems, especially coolest red dwarfs, are just beginning to be investigated, so they are very exciting targets for future exoplanet research.”
But the team noted a key outcome of their findings is how similar planets orbiting red dwarf stars may be to planets orbiting solar-type stars. In fact, this is the first time that researchers have shown a similar radius gap in both groups.
"This is a unique finding, and many theoretical astronomers are now investigating what causes this gap," Hirano said.
According to NASA's exoplanet archive, there are 2,342 Kepler confirmed planets as of March 13, 2018.
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