HD 15906 b
HD 15906 b is a mini-Neptune orbiting the K V star HD 15906 in the constellation Cetus. It lies about 149 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is HD 15906 b?
HD 15906 b has a radius of 2.24 times that of Earth.
Is HD 15906 b in the Habitable Zone?
HD 15906 b orbits inside the inner edge of the habitable zone of HD 15906. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 15906: 0.411–1.005 AU (conservative: 0.521–0.953 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 15906 b
The equilibrium temperature of HD 15906 b is about 668 K (395 °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 33.14 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 15906 b — one full orbit around HD 15906 — lasts 10.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.090 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.11).
How Was HD 15906 b Discovered?
HD 15906 b was discovered in 2023 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 15906 b?
HD 15906 b is 148.6 light-years (45.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1878. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,615,360 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. HD 15906 b scores 0.28, ranking #2,217 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 15906
HD 15906
- Spectral type
- K V
- Surface temperature
- 4,757 K (Sun: 5,772 K)
- Mass
- 0.79 M☉
- Radius
- 0.76 R☉
- Luminosity
- 0.2700 L☉
The HD 15906 Planetary System
HD 15906 b is one of 2 known planets in the HD 15906 system. Its siblings:
- HD 15906 c (Mini Neptune)
HD 15906 b — Complete Data
| Radius | 2.240 Earth radii (0.200 Jupiter radii) |
|---|---|
| Orbital period | 10.92 days |
| Orbital distance | 0.090 AU |
| Eccentricity | 0.110 |
| Equilibrium temperature | 668 K (395 °C) |
| Stellar irradiation | 33.14× Earth |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 148.6 light-years (45.6 parsecs) |
| Constellation | Cetus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-06-27. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 15906 b
Is HD 15906 b habitable?
No — HD 15906 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 15906 b?
HD 15906 b is about 149 light-years from Earth in the constellation Cetus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,615,360 years to get there.
How big is HD 15906 b compared to Earth?
HD 15906 b has 2.24 times the radius of Earth.
How long is a year on HD 15906 b?
One orbit around HD 15906 takes 10.9 Earth days — short enough that 33 of its years would fit into one Earth year.
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