Kepler-1801 c
Kepler-1801 c is a mini-Neptune orbiting Kepler-1801 in the constellation Cygnus. It lies about 2,738 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-1801 c?
Kepler-1801 c has a radius of 2.91 times that of Earth.
Is Kepler-1801 c in the Habitable Zone?
Kepler-1801 c orbits inside the inner edge of the habitable zone of Kepler-1801. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-1801: 0.728–1.717 AU (conservative: 0.922–1.627 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-1801 c
The equilibrium temperature of Kepler-1801 c is about 371 K (98 °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 4.47 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-1801 c — one full orbit around Kepler-1801 — lasts 116.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.457 AU — comparable to the inner Solar System.
How Was Kepler-1801 c Discovered?
Kepler-1801 c 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-1801 c?
Kepler-1801 c is 2,737.5 light-years (839.3 parsecs) from Earth. Light arriving here tonight left the planet about 2,738 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 48,180,000 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-1801 c scores 0.51, ranking #240 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-1801
Kepler-1801
- Surface temperature
- 5,738 K (Sun: 5,772 K)
- Mass
- 0.94 M☉
- Radius
- 0.98 R☉
The Kepler-1801 Planetary System
Kepler-1801 c is one of 2 known planets in the Kepler-1801 system. Its siblings:
- Kepler-1801 b (Mini Neptune)
Kepler-1801 c — Complete Data
| Radius | 2.910 Earth radii (0.260 Jupiter radii) |
|---|---|
| Orbital period | 116.58 days |
| Orbital distance | 0.457 AU |
| Equilibrium temperature | 371 K (98 °C) |
| Stellar irradiation | 4.47× Earth |
| Earth Similarity Index | 0.51 |
| Distance from Earth | 2,737.5 light-years (839.3 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-1801 c
Is Kepler-1801 c habitable?
No — Kepler-1801 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-1801 c?
Kepler-1801 c is about 2,738 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 48,180,000 years to get there.
How big is Kepler-1801 c compared to Earth?
Kepler-1801 c has 2.91 times the radius of Earth.
How long is a year on Kepler-1801 c?
One orbit around Kepler-1801 takes 116.6 Earth days.
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