Kepler-1981 b
Kepler-1981 b is a cold gas giant orbiting Kepler-1981 in the constellation Lyra. It lies about 2,151 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-1981 b?
Kepler-1981 b has a radius of 9.23 times that of Earth, or 0.82 times the radius of Jupiter.
Is Kepler-1981 b in the Habitable Zone?
Kepler-1981 b orbits inside the inner edge of the habitable zone of Kepler-1981. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-1981: 2.318–5.448 AU (conservative: 2.936–5.165 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on Kepler-1981 b
The equilibrium temperature of Kepler-1981 b is about 390 K (117 °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 5.45 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-1981 b — one full orbit around Kepler-1981 — lasts 453.5 Earth days, longer than an Earth year. It orbits at an average distance of 1.329 AU.
How Was Kepler-1981 b Discovered?
Kepler-1981 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-1981 b?
Kepler-1981 b is 2,150.7 light-years (659.4 parsecs) from Earth. Light arriving here tonight left the planet about 2,151 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 37,852,320 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-1981 b scores 0.43, ranking #389 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-1981
Kepler-1981
- Surface temperature
- 5,874 K (Sun: 5,772 K)
- Mass
- 1.52 M☉
- Radius
- 3.01 R☉
Planetary System
Kepler-1981 b is the only planet known to orbit Kepler-1981 so far.
Kepler-1981 b — Complete Data
| Radius | 9.230 Earth radii (0.823 Jupiter radii) |
|---|---|
| Orbital period | 453.54 days |
| Orbital distance | 1.329 AU |
| Equilibrium temperature | 390 K (117 °C) |
| Stellar irradiation | 5.45× Earth |
| Earth Similarity Index | 0.43 |
| Distance from Earth | 2,150.7 light-years (659.4 parsecs) |
| Constellation | Lyra |
| 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-1981 b
Is Kepler-1981 b habitable?
No — Kepler-1981 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-1981 b?
Kepler-1981 b is about 2,151 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 37,852,320 years to get there.
How big is Kepler-1981 b compared to Earth?
Kepler-1981 b has 9.23 times the radius of Earth.
How long is a year on Kepler-1981 b?
One orbit around Kepler-1981 takes 453.5 Earth days.
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