Kepler-1869 c
Kepler-1869 c is a terrestrial planet orbiting Kepler-1869 in the constellation Cygnus. It lies about 369 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-1869 c?
Kepler-1869 c has a radius of 0.74 times that of Earth.
Is Kepler-1869 c in the Habitable Zone?
Kepler-1869 c orbits inside the inner edge of the habitable zone of Kepler-1869. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-1869: 0.683–1.607 AU (conservative: 0.865–1.524 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-1869 c
The equilibrium temperature of Kepler-1869 c is about 1,455 K (1,182 °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 1,057 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-1869 c — one full orbit around Kepler-1869 — lasts just 41.2 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.028 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-1869 c Discovered?
Kepler-1869 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-1869 c?
Kepler-1869 c is 368.6 light-years (113.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1658. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,487,360 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-1869 c scores 0.29, ranking #2,026 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-1869
Kepler-1869
- Surface temperature
- 5,808 K (Sun: 5,772 K)
- Mass
- 0.99 M☉
- Radius
- 0.90 R☉
The Kepler-1869 Planetary System
Kepler-1869 c is one of 2 known planets in the Kepler-1869 system. Its siblings:
- Kepler-1869 b (Terrestrial)
Kepler-1869 c — Complete Data
| Radius | 0.740 Earth radii (0.066 Jupiter radii) |
|---|---|
| Orbital period | 1.72 days |
| Orbital distance | 0.028 AU |
| Equilibrium temperature | 1,455 K (1,182 °C) |
| Stellar irradiation | 1,056.84× Earth |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 368.6 light-years (113.0 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-1869 c
Is Kepler-1869 c habitable?
No — Kepler-1869 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-1869 c?
Kepler-1869 c is about 369 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,487,360 years to get there.
How big is Kepler-1869 c compared to Earth?
Kepler-1869 c has 0.74 times the radius of Earth.
How long is a year on Kepler-1869 c?
One orbit around Kepler-1869 takes 1.7 Earth days — short enough that 213 of its years would fit into one Earth year.
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