HD 219134 b
HD 219134 b is a super-Earth orbiting HD 219134 in the constellation Cassiopeia. It lies about 21 light-years from Earth and was discovered in 2015 using the radial velocity method.
How Big Is HD 219134 b?
HD 219134 b has a radius of 1.60 times that of Earth. Its mass is 4.7 times that of Earth, giving it a density of 6.34 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is HD 219134 b in the Habitable Zone?
HD 219134 b orbits inside the inner edge of the habitable zone of HD 219134. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 219134: 0.408–1.000 AU (conservative: 0.517–0.948 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 219134 b
The equilibrium temperature of HD 219134 b is about 1,015 K (742 °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 176 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 219134 b — one full orbit around HD 219134 — lasts 3.09 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.039 AU — closer to its star than Mercury is to the Sun.
How Was HD 219134 b Discovered?
HD 219134 b was discovered in 2015 using the radial velocity method, with observations from Roque de los Muchachos 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 219134 b?
HD 219134 b is 21.3 light-years (6.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 2005. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 374,880 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 219134 b scores 0.28, ranking #2,182 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 219134
HD 219134
- Surface temperature
- 4,699 K (Sun: 5,772 K)
- Mass
- 0.81 M☉
- Radius
- 0.78 R☉
- Luminosity
- 0.2646 L☉
- Age
- 11.0 billion years (Sun: 4.6)
The HD 219134 Planetary System
HD 219134 b is one of 6 known planets in the HD 219134 system. Its siblings:
- HD 219134 c (Super Earth)
- HD 219134 d (Super Earth)
- HD 219134 f (Super Earth)
- HD 219134 g (Neptune-like)
- HD 219134 h (Cold Gas Giant)
HD 219134 b — Complete Data
| Radius | 1.602 Earth radii (0.143 Jupiter radii) |
|---|---|
| Mass | 4.74 Earth masses (0.015 Jupiter masses) |
| Density | 6.34 g/cm³ (Earth: 5.51) |
| Orbital period | 3.09 days |
| Orbital distance | 0.039 AU |
| Equilibrium temperature | 1,015 K (742 °C) |
| Stellar irradiation | 176.20× Earth |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 21.3 light-years (6.5 parsecs) |
| Constellation | Cassiopeia |
| Discovery method | Radial Velocity |
| Discovery facility | Roque de los Muchachos Observatory |
| Discovery year | 2015 |
Data: NASA Exoplanet Archive, last updated 2017-03-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 219134 b
Is HD 219134 b habitable?
No — HD 219134 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 219134 b?
HD 219134 b is about 21 light-years from Earth in the constellation Cassiopeia. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 374,880 years to get there.
How big is HD 219134 b compared to Earth?
HD 219134 b has 1.60 times the radius of Earth and about 4.7 times its mass.
How long is a year on HD 219134 b?
One orbit around HD 219134 takes 3.1 Earth days — short enough that 118 of its years would fit into one Earth year.
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