A team of astronomers at the Massachusetts Institute of Technology (MIT) has discovered one of the closest multi-planet systems to ours . The two super-Earths orbit the cool M-dwarf star HD 260655, and the entire system is located 10 parsecs, or about 33 light-years away.
The first planet, HD 260655 b , orbits the star every 2.8 days and has about 1.2 times the mass of Earth, but about twice the mass. The HD 260655 c is further along. It orbits the star in 5.7 days, has about three Earth masses and is 1.5 times larger. The discovery was presented at the 240th Meeting of the American Astronomical Society.
While this dwarf star is much cooler than our Sun, the planets being much closer causes them to be hotter and stay outside the “habitable zone.” The innermost planet is estimated to have scorching temperatures of 437°C , while the outer planet is estimated to be around 287°C .
” We think this range is outside the habitable zone and is too hot for liquid water to exist on the surface ,” said Michelle Kunimoto , a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Studies and lead scientist on the discovery.
The planets may not be habitable, but their relative proximity to us and the brightness of their stars will allow astronomers to study them in detail and perhaps reveal features of any atmospheres they may have.
” Both planets in this system are considered among the best targets for atmospheric study because of the brightness of their stars, ” says Kunimoto . will be great test beds for these discoveries. ”
Two planets may not be alone
Co-author Avi Shporer adds that “there may be more planets in the system ,” adds: “ There are many multi-planet systems that host five or six planets, especially around smaller stars like this one. Hopefully we’ll find more and one might be in the habitable zone. This is an optimistic thought. ”
The system was first identified using NASA’s planet hunter Transiting Exoplanet Survey Satellite (TESS) , which describes dips in brightness as planets regularly pass in front of their stars. To confirm that the planets were indeed there, the team needed to use an independent method. They looked at observations of the star HD 260655 to identify potential wobbles caused by the gravitational pull of the planets.
” Every planet orbiting a star will have some gravitational effect on its star ,” Kunimoto says .
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