Kepler-101 b
Kepler-101 b is a Neptune-like planet orbiting the G3 IV star Kepler-101 in the constellation Draco. It lies about 3,027 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-101 b?
Kepler-101 b has a radius of 5.77 times that of Earth, or 0.51 times the radius of Jupiter. Its mass is 51.1 times that of Earth, giving it a density of 1.45 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-101 b in the Habitable Zone?
Kepler-101 b orbits inside the inner edge of the habitable zone of Kepler-101. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-101: 1.134–2.679 AU (conservative: 1.436–2.540 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-101 b
The equilibrium temperature of Kepler-101 b is about 1,513 K (1,240 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on Kepler-101 b — one full orbit around Kepler-101 — lasts 3.49 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.047 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.09).
How Was Kepler-101 b Discovered?
Kepler-101 b was discovered in 2014 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-101 b?
Kepler-101 b is 3,026.7 light-years (928.0 parsecs) from Earth. Light arriving here tonight left the planet about 3,027 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 53,269,920 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-101 b scores 0.14, ranking #4,265 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-101
Kepler-101
- Spectral type
- G3 IV
- Surface temperature
- 5,667 K (Sun: 5,772 K)
- Mass
- 1.17 M☉
- Radius
- 1.56 R☉
- Age
- 5.9 billion years (Sun: 4.6)
The Kepler-101 Planetary System
Kepler-101 b is one of 2 known planets in the Kepler-101 system. Its siblings:
- Kepler-101 c (Terrestrial)
Kepler-101 b — Complete Data
| Radius | 5.770 Earth radii (0.510 Jupiter radii) |
|---|---|
| Mass | 51.10 Earth masses (0.160 Jupiter masses) |
| Density | 1.45 g/cm³ (Earth: 5.51) |
| Orbital period | 3.49 days |
| Orbital distance | 0.047 AU |
| Eccentricity | 0.086 |
| Equilibrium temperature | 1,513 K (1,240 °C) |
| Earth Similarity Index | 0.14 |
| Distance from Earth | 3,026.7 light-years (928.0 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-09-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-101 b
Is Kepler-101 b habitable?
No — Kepler-101 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-101 b?
Kepler-101 b is about 3,027 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 53,269,920 years to get there.
How big is Kepler-101 b compared to Earth?
Kepler-101 b has 5.77 times the radius of Earth and about 51.1 times its mass.
How long is a year on Kepler-101 b?
One orbit around Kepler-101 takes 3.5 Earth days — short enough that 105 of its years would fit into one Earth year.
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