![Kepler-37 b: 0.31 Times Earth](https://cdn.slatesource.com/9/e/3/9e3d7f91-b5b3-4e43-97ca-81d4635f916d.webp)

# Kepler-37 b: 0.31 Times Earth

- [Made in Slatesource](https://slatesource.com/@steph/kepler-37-b-0-31-times-earth)
- By [Steph](https://slatesource.com/@steph)
- Created on Sep 19, 2026

## Terrestrial around Kepler-37

It is 0.31 times Earth's radius, closest in size to Mars, and 0.8 times Earth's mass, at 140.00 g/cm3, denser than Earth. A year there lasts 13.37 days, on an orbit 4 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 718 K, hot enough to melt lead. The host star Kepler-37 runs at 5357 K with 0.79 times the Sun's mass.

**140.0** g/cm3: denser than iron at Earth surface pressure

journey·3 Planets

# Kepler-37 from the inside out

Orbit

/

Planet

"terrestrial, 718 K.

"terrestrial, 615 K.

"mini-Neptune, 499 K.

Radius

0.31 Earth radii

Mass

0.8 Earth masses

Equilibrium temperature

718 K (measured)

One year

13.37 days

Orbit radius

0.1019 AU

Host star

Kepler-37 at 5357 K

Distance

208 light-years

Starlight blocked

0.001% at each transit

What you get from the shadow

The fraction of starlight blocked sets the radius against the star's.

Found by Kepler in 2013. 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-37 has 4 known planets. Planets in company tug on each other, and those tugs are measurable, which is how masses get pinned down without a wobble.

Size from the shadow, mass from elsewhere. Most transiting planets never get the second half, and without it composition stays a guess.

[NASA Exoplanet Archive: every published measurement of this planet](https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-37%20b?utm_source=slatesource)