HD 80606 b
HD 80606 b is a cold gas giant orbiting HD 80606 in the constellation Ursa Major. It lies about 217 light-years from Earth and was discovered in 2001 using the radial velocity method.
How Big Is HD 80606 b?
HD 80606 b has a radius of 11.57 times that of Earth, or 1.03 times the radius of Jupiter. Its mass is 1,323 times that of Earth.
Is HD 80606 b in the Habitable Zone?
HD 80606 b orbits inside the inner edge of the habitable zone of HD 80606. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 80606: 0.740–1.755 AU (conservative: 0.938–1.663 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on HD 80606 b — one full orbit around HD 80606 — lasts 111.4 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.460 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.93), swinging dramatically closer to and farther from its star.
How Was HD 80606 b Discovered?
HD 80606 b was discovered in 2001 using the radial velocity method, with observations from Multiple Observatories.
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 80606 b?
HD 80606 b is 216.8 light-years (66.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1810. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,815,680 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 80606 b scores 0.15, ranking #4,216 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 80606
HD 80606 b belongs to a system of 2 stars; it orbits HD 80606.
HD 80606
- Surface temperature
- 5,565 K (Sun: 5,772 K)
- Mass
- 1.05 M☉
- Radius
- 1.05 R☉
Planetary System
HD 80606 b is the only planet known to orbit HD 80606 so far.
HD 80606 b — Complete Data
| Radius | 11.568 Earth radii (1.032 Jupiter radii) |
|---|---|
| Mass | 1,323.47 Earth masses (4.164 Jupiter masses) |
| Orbital period | 111.44 days |
| Orbital distance | 0.460 AU |
| Eccentricity | 0.932 |
| Earth Similarity Index | 0.15 |
| Distance from Earth | 216.8 light-years (66.5 parsecs) |
| Constellation | Ursa Major |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2001 |
Data: NASA Exoplanet Archive, last updated 2025-12-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 80606 b
Is HD 80606 b habitable?
No — HD 80606 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 80606 b?
HD 80606 b is about 217 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,815,680 years to get there.
How big is HD 80606 b compared to Earth?
HD 80606 b has 11.57 times the radius of Earth and about 1,323 times its mass.
How long is a year on HD 80606 b?
One orbit around HD 80606 takes 111.4 Earth days.
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