Kepler-138 b: 0.64 Times Earth
Terrestrial around Kepler-138
It is 0.64 times Earth's radius, closest in size to Mars, and 0.1 times Earth's mass, at 1.70 g/cm3, less dense than Earth. A year there lasts 10.31 days, on an orbit 5 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 452 K, hotter than any desert. The host star Kepler-138 runs at 3841 K with 0.54 times the Sun's mass.
Kepler-138 from the inside out
Orbit
/
Planet
Radius
0.64 Earth radii
Mass
0.1 Earth masses
Equilibrium temperature
452 K (measured)
One year
10.31 days
Orbit radius
0.0753 AU
Host star
Kepler-138 at 3841 K
Distance
218 light-years
Starlight blocked
0.012% at each transit
0.64xEarth: smaller than Venus
What you get from the shadow
Block a known fraction of a known star and you have measured a width.
Found by Kepler in 2014. Kepler watched a single field continuously, so it found the planets that come round often. A world with a long year simply never repeated within the mission.
Kepler-138 has 4 known planets. Systems like this are the ones where architecture can be studied instead of guessed at.
Two independent measurements sit behind this page: a dip in starlight for the size, and something else entirely for the mass. Together they make a density.
