tau Boo b
tau Boo b is a hot Jupiter orbiting tau Boo in the constellation Boötes. It lies about 51 light-years from Earth and was discovered in 1996 using the radial velocity method.
Is tau Boo b in the Habitable Zone?
tau Boo b orbits inside the inner edge of the habitable zone of tau Boo. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of tau Boo: 1.288–2.992 AU (conservative: 1.632–2.837 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 tau Boo b — one full orbit around tau Boo — lasts 3.31 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.049 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.011).
How Was tau Boo b Discovered?
tau Boo b was discovered in 1996 using the radial velocity method, with observations from Lick 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 tau Boo b?
tau Boo b is 51.1 light-years (15.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 1975. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 899,360 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. tau Boo b scores 0.07, ranking #4,932 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: tau Boo
tau Boo b belongs to a system of 2 stars; it orbits tau Boo.
tau Boo
- Surface temperature
- 6,466 K (Sun: 5,772 K)
- Mass
- 1.32 M☉
- Radius
- 1.43 R☉
- Luminosity
- 3.2024 L☉
Planetary System
tau Boo b is the only planet known to orbit tau Boo so far.
tau Boo b — Complete Data
| Mass (best estimate) | 1,373.03 Earth masses |
|---|---|
| Orbital period | 3.31 days |
| Orbital distance | 0.049 AU |
| Eccentricity | 0.011 |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 51.1 light-years (15.7 parsecs) |
| Constellation | Boötes |
| Discovery method | Radial Velocity |
| Discovery facility | Lick Observatory |
| Discovery year | 1996 |
Data: NASA Exoplanet Archive, last updated 2015-04-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About tau Boo b
Is tau Boo b habitable?
No — tau Boo b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is tau Boo b?
tau Boo b is about 51 light-years from Earth in the constellation Boötes. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 899,360 years to get there.
How long is a year on tau Boo b?
One orbit around tau Boo takes 3.3 Earth days — short enough that 110 of its years would fit into one Earth year.
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