:INFO
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.

:JOURNEY
Kepler-138 from the inside out
1 0.075 AU
2 0.091 AU
3 0.129 AU

:STATS
[icon:TARGET] Radius | 0.64 Earth radii
[icon:CHART] Mass | 0.1 Earth masses
[icon:FIRE] Equilibrium temperature | 452 K (measured)
[icon:CLOCK] One year | 10.31 days
[icon:BOLT] Orbit radius | 0.0753 AU
[icon:STAR] Host star | Kepler-138 at 3841 K
[icon:USERS] Distance | 218 light-years
[icon:TRENDING_DOWN] Starlight blocked | 0.012% at each transit

:COUNTER
0.64x Earth: smaller than Venus

:PATH
What you get from the shadow
Block a known fraction of a known star and you have measured a width.

:NOTE
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.

:NOTE
Kepler-138 has 4 known planets. Systems like this are the ones where architecture can be studied instead of guessed at.

:NOTE
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.

:LINK
https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-138%20b
NASA Exoplanet Archive: source data, including the values not used here