Astronomers using data from NASA's Kepler Space Telescope have discovered a planet about twice the size of Earth that orbits a star in the low-mass binary system K2-288 (also known as EPIC 210693462, LP 413-32, NLTT 11596 and 2MASS J03414639 + 1816082). Nicknamed K2-288Bb, the strange world could be rocky or it could be a gaseous planet similar to Neptune.
Located 226 light-years away, in the constellation of Taurus, the newly discovered planet orbits the weakest member of the binary system K2-288.
This system contains a pair of dark and M-type stars separated by approximately 5.1 trillion miles (8.2 billion kilometers), approximately six times the distance between Saturn and the Sun.
The brightest star, K2-288A, is about half as massive and large as the Sun, while its companion, K2-288B, is about one-third the mass and size of the Sun.
"The candidate planet was first identified by citizen scientists who used Exoplanet Explorers hosted on the Zooniverse platform," said University of Chicago graduate student Adina Feinstein and colleagues.
"The follow-up observations and detailed analyzes validate the planet and indicate that it probably orbits the secondary star in a period of 31.4 days."
"This orbit places K2-288Bb in or near the habitable zone of its low-mass host star."
K2-288Bb has a radius of about 1.9 times that of Earth, which places it in the so-called Fulton gap, a likely transition zone between rocky super-Earths and gaseous subnepts.
"Among the planets orbiting near their stars, there is a curious shortage of worlds between 1.5 and twice the size of Earth," the astronomers explained.
"This is probably the result of intense starlight that breaks down atmospheric molecules and erodes the atmospheres of some planets over time, leaving behind two populations."
"Since the radius of K2-288Bb places it in this gap, it can provide a case study of planetary evolution within this size range."
The discovery is reported in an article in the Astronomical Magazine.
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