An international team of astronomers has discovered a rocky exoplanet with an orbital period of 8.9 hours.
EPIC 228732031b orbits so close to its parent star that a new year comes every 8.9 hours. Image credit: NASA’s Goddard Space Flight Center / TESS / MIT / Lincoln Laboratory.
The newly detected planet, designated EPIC 228732031b, is 1.81 times the size of Earth and 6.5 times more massive, resulting in a mean density of 6 g/cm3.
The alien world belongs to a class of planets called ultra-short-period exoplanets that have orbits of less than a day.
The planet whizzes around its host star every 8 hours and 54 minutes.
The star, called EPIC 228732031, is a G-type (yellow) dwarf with about 84% the mass of the Sun.
It is nearly 568 light-years away and is both very hot (5,200 K) and very bright (V=12).
The G-type dwarf star EPIC 228732031. Image credit: Dai et al, arXiv: 1710.00076.
According to the astronomers, EPIC 228732031b is likely far too hot to be habitable for life as we know it.
The planet was found using NASA’s prolonged Kepler mission known as K2.
The detection was made using the now common transit technique, in which astronomers calculate a planet’s mass and size based on the periodic dimming of starlight the exoplanet creates when it passes in front of its host star.
A second planet with a longer orbit might also circle EPIC 228732031.
“Many of the detected ultra-short-period planets have planetary companions,” the scientists said.
“Although K2 light curve did not reveal another transiting planet, there could be the signal of a non-transiting planet lurking in our radial velocity dataset.”
A paper describing the discovery will appear in the Astronomical Journal and is now available online at arXiv.org.
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Fei Dai et al. 2017. The discovery and mass measurement of a new ultra-short-period planet: EPIC 228732031b. AJ, in press; arXiv: 1710.00076
