Kepler-1987 b
Kepler-1987 b is a terrestrial planet orbiting Kepler-1987 in the constellation Cygnus. It lies about 1,943 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-1987 b?
Kepler-1987 b has a radius of 1.23 times that of Earth.
Is Kepler-1987 b in the Habitable Zone?
Kepler-1987 b orbits inside the inner edge of the habitable zone of Kepler-1987. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-1987: 0.385–0.940 AU (conservative: 0.488–0.891 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-1987 b
The equilibrium temperature of Kepler-1987 b is about 997 K (724 °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. It receives 233 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-1987 b — one full orbit around Kepler-1987 — lasts 2.35 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.032 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-1987 b Discovered?
Kepler-1987 b was discovered in 2023 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-1987 b?
Kepler-1987 b is 1,942.9 light-years (595.7 parsecs) from Earth. Light arriving here tonight left the planet about 1,943 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 34,195,040 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-1987 b scores 0.29, ranking #1,561 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-1987
Kepler-1987
- Surface temperature
- 4,769 K (Sun: 5,772 K)
- Mass
- 0.80 M☉
- Radius
- 0.71 R☉
The Kepler-1987 Planetary System
Kepler-1987 b is one of 4 known planets in the Kepler-1987 system. Its siblings:
- Kepler-1987 c (Super Earth)
- Kepler-1987 d (Mini Neptune)
- Kepler-1987 e (Super Earth)
Kepler-1987 b — Complete Data
| Radius | 1.230 Earth radii (0.110 Jupiter radii) |
|---|---|
| Orbital period | 2.35 days |
| Orbital distance | 0.032 AU |
| Equilibrium temperature | 997 K (724 °C) |
| Stellar irradiation | 233.38× Earth |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 1,942.9 light-years (595.7 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2017-05-08. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-1987 b
Is Kepler-1987 b habitable?
No — Kepler-1987 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-1987 b?
Kepler-1987 b is about 1,943 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 34,195,040 years to get there.
How big is Kepler-1987 b compared to Earth?
Kepler-1987 b has 1.23 times the radius of Earth.
How long is a year on Kepler-1987 b?
One orbit around Kepler-1987 takes 2.3 Earth days — short enough that 156 of its years would fit into one Earth year.
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