Kepler-407b is a transiting Earth-size planet detected by
NASA’s Kepler space telescope. Measuring 1.07 ± 0.02 times the radius of Earth,
Kepler-407b also whizzes around its host star, a Sun-like star, in an extremely
close-in orbit with a period of only 16 hours. At such close proximity to its
host star, temperatures on the planet’s day side are expected to reach well
over 2000 K.
Kepler-407b is most likely tidally-locked with the same side
of the planet always pointed towards its host star. A lave ocean could exist on
the planet’s intensely hot day side where temperatures are too high for rock
material to remain solid. Kepler-407b joins a growing list of planets with
orbital periods less than 24 hours. Other similar planets include Kepler-10b
and Kepler-78b.
Follow-up radial velocity (RV) measurements to determine the
mass of Kepler-407b could only provide a one sigma upper limit of 1.7 times the
mass of Earth. These RV measurements also detected the partial orbit of an
outer, non-transiting planet, hereafter identified as Kepler-407c. Given that
only a quarter of a potentially ~10 year long orbit was measured by RV, the
planet’s orbit and mass could only be weakly constrained.
Kepler-407c is estimated to have an orbital period of 3000 ±
500 days and somewhere between 5 to 20 times the mass of Jupiter. However, depending
on the inclination of its orbit, Kepler-407c could also be a more massive
object such as a brown dwarf or even a red dwarf star. Future RV measurements
will be needed to better constrain the masses of both Kepler-407b and c.
Reference:
Marcy et al. (2014), “Masses, Radii, and Orbits of Small
Kepler Planets: The Transition from Gaseous to Rocky Planets”, arXiv:1401.4195
[astro-ph.EP]