HD 211403 b
HD 211403 b is a cold gas giant orbiting the F7 V star HD 211403 in the constellation Cepheus. It lies about 271 light-years from Earth and was discovered in 2021 using the radial velocity method.
Is HD 211403 b in the Habitable Zone?
HD 211403 b orbits inside the inner edge of the habitable zone of HD 211403. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 211403: 1.035–2.412 AU (conservative: 1.311–2.287 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 211403 b
The equilibrium temperature of HD 211403 b is about 380 K (107 °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 3.44 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 211403 b — one full orbit around HD 211403 — lasts 223.8 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.768 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.08).
How Was HD 211403 b Discovered?
HD 211403 b was discovered in 2021 using the radial velocity method, with observations from Haute-Provence Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is HD 211403 b?
HD 211403 b is 271.0 light-years (83.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1755. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,769,600 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 211403 b scores 0.26, ranking #2,776 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 211403
HD 211403
- Spectral type
- F7 V
- Surface temperature
- 6,273 K (Sun: 5,772 K)
- Mass
- 1.20 M☉
- Radius
- 1.21 R☉
Planetary System
HD 211403 b is the only planet known to orbit HD 211403 so far.
HD 211403 b — Complete Data
| Mass (best estimate) | 1,760.77 Earth masses |
|---|---|
| Orbital period | 223.80 days |
| Orbital distance | 0.768 AU |
| Eccentricity | 0.084 |
| Equilibrium temperature | 380 K (107 °C) |
| Stellar irradiation | 3.44× Earth |
| Earth Similarity Index | 0.26 |
| Distance from Earth | 271.0 light-years (83.1 parsecs) |
| Constellation | Cepheus |
| Discovery method | Radial Velocity |
| Discovery facility | Haute-Provence Observatory |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-10-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 211403 b
Is HD 211403 b habitable?
No — HD 211403 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 211403 b?
HD 211403 b is about 271 light-years from Earth in the constellation Cepheus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,769,600 years to get there.
How long is a year on HD 211403 b?
One orbit around HD 211403 takes 223.8 Earth days.
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