Kepler-37 d
Kepler-37 d is a puffy low-density planet orbiting Kepler-37 in the constellation Lyra. It lies about 209 light-years from Earth and was discovered in 2013 using the transit method.
How Big Is Kepler-37 d?
Kepler-37 d has a radius of 2.03 times that of Earth. Its mass is 2.0 times that of Earth, giving it a density of 1.30 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-37 d in the Habitable Zone?
Kepler-37 d orbits inside the inner edge of the habitable zone of Kepler-37. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-37: 0.522–1.244 AU (conservative: 0.661–1.180 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-37 d
The equilibrium temperature of Kepler-37 d is about 499 K (226 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 10.39 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-37 d — one full orbit around Kepler-37 — lasts 39.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.211 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.10).
How Was Kepler-37 d Discovered?
Kepler-37 d was discovered in 2013 using the transit method, with observations from Kepler.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is Kepler-37 d?
Kepler-37 d is 208.5 light-years (63.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1818. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,669,600 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. Kepler-37 d scores 0.37, ranking #657 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-37
Kepler-37
- Surface temperature
- 5,357 K (Sun: 5,772 K)
- Mass
- 0.79 M☉
- Radius
- 0.79 R☉
- Age
- 7.6 billion years (Sun: 4.6)
The Kepler-37 Planetary System
Kepler-37 d is one of 4 known planets in the Kepler-37 system. Its siblings:
- Kepler-37 b (Terrestrial)
- Kepler-37 c (Terrestrial)
- Kepler-37 e
Kepler-37 d — Complete Data
| Radius | 2.030 Earth radii (0.181 Jupiter radii) |
|---|---|
| Mass | 2.00 Earth masses (0.006 Jupiter masses) |
| Density | 1.30 g/cm³ (Earth: 5.51) |
| Orbital period | 39.79 days |
| Orbital distance | 0.211 AU |
| Eccentricity | 0.100 |
| Equilibrium temperature | 499 K (226 °C) |
| Stellar irradiation | 10.39× Earth |
| Earth Similarity Index | 0.37 |
| Distance from Earth | 208.5 light-years (63.9 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-37 d
Is Kepler-37 d habitable?
No — Kepler-37 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-37 d?
Kepler-37 d is about 209 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,669,600 years to get there.
How big is Kepler-37 d compared to Earth?
Kepler-37 d has 2.03 times the radius of Earth and about 2.0 times its mass.
How long is a year on Kepler-37 d?
One orbit around Kepler-37 takes 39.8 Earth days.
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