HD 207897 b
HD 207897 b is a super-Earth orbiting HD 207897 in the constellation Cepheus. It lies about 92 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is HD 207897 b?
HD 207897 b has a radius of 2.34 times that of Earth. Its mass is 14.8 times that of Earth, giving it a density of 6.29 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is HD 207897 b in the Habitable Zone?
HD 207897 b orbits inside the inner edge of the habitable zone of HD 207897. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 207897: 0.480–1.155 AU (conservative: 0.608–1.095 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 207897 b
The equilibrium temperature of HD 207897 b is about 582 K (309 °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.
Orbit and Year Length
A year on HD 207897 b — one full orbit around HD 207897 — lasts 16.2 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.117 AU — closer to its star than Mercury is to the Sun.
How Was HD 207897 b Discovered?
HD 207897 b was discovered in 2021 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 HD 207897 b?
HD 207897 b is 92.3 light-years (28.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1934. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,624,480 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. HD 207897 b scores 0.28, ranking #2,345 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 207897
HD 207897
- Surface temperature
- 5,106 K (Sun: 5,772 K)
- Mass
- 0.82 M☉
- Radius
- 0.78 R☉
- Luminosity
- 0.3790 L☉
- Age
- 4.7 billion years (Sun: 4.6)
Planetary System
HD 207897 b is the only planet known to orbit HD 207897 so far.
HD 207897 b — Complete Data
| Radius | 2.343 Earth radii (0.209 Jupiter radii) |
|---|---|
| Mass | 14.80 Earth masses (0.047 Jupiter masses) |
| Density | 6.29 g/cm³ (Earth: 5.51) |
| Orbital period | 16.20 days |
| Orbital distance | 0.117 AU |
| Equilibrium temperature | 582 K (309 °C) |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 92.3 light-years (28.3 parsecs) |
| Constellation | Cepheus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2024-07-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 207897 b
Is HD 207897 b habitable?
No — HD 207897 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 207897 b?
HD 207897 b is about 92 light-years from Earth in the constellation Cepheus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,624,480 years to get there.
How big is HD 207897 b compared to Earth?
HD 207897 b has 2.34 times the radius of Earth and about 14.8 times its mass.
How long is a year on HD 207897 b?
One orbit around HD 207897 takes 16.2 Earth days — short enough that 23 of its years would fit into one Earth year.
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