Astronomers using data from NASA’s Kepler Space Telescope have discovered a planet roughly twice the size of Earth orbiting a star in the low-mass binary system K2-288 (also known as EPIC 210693462, LP 413-32, NLTT 11596 and 2MASS J03414639+1816082). Dubbed K2-288Bb, the alien world could be rocky or could be a gaseous planet similar to Neptune.
Located 226 light-years away in the constellation Taurus, the newly-discovered planet orbits the fainter member of the K2-288 binary system.
This system contains a pair of dim, cool M-type stars separated by about 5.1 billion miles (8.2 billion km), roughly six times the distance between Saturn and the Sun.
The brighter star, K2-288A, is about half as massive and large as the Sun, while its companion, K2-288B, is about one-third the Sun’s mass and size.
“The candidate planet was first identified by citizen scientists using Exoplanet Explorers hosted on the Zooniverse platform,” said University of Chicago graduate student Adina Feinstein and colleagues.
“Follow-up observations and detailed analyses validate the planet and indicate that it likely orbits the secondary star on a 31.4-day period.”
“This orbit places K2-288Bb in or near the habitable zone of its low-mass host star.”
“Among planets that orbit close to their stars, there’s a curious dearth of worlds between about 1.5 and two times Earth’s size,” the astronomers explained.
“This is likely the result of intense starlight breaking up atmospheric molecules and eroding away the atmospheres of some planets over time, leaving behind two populations.”
“Since K2-288Bb’s radius places it in this gap, it may provide a case study of planetary evolution within this size range.”
The discovery is reported in a paper in the Astronomical Journal.
Adina D. Feinstein et al. 2019. K2-288Bb: A Small Temperate Planet in a Low-mass Binary System Discovered by Citizen Scientists. AJ 157, 40; doi: 10.3847/1538-3881/aafa70