eps Tau b
eps Tau b is a cold gas giant orbiting the K0 III star eps Tau in the constellation Taurus. It lies about 155 light-years from Earth and was discovered in 2006 using the radial velocity method.
Is eps Tau b in the Habitable Zone?
eps Tau b orbits inside the inner edge of the habitable zone of eps Tau. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of eps Tau: 6.962–16.917 AU (conservative: 8.818–16.039 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 eps Tau b — one full orbit around eps Tau — lasts 585.8 Earth days, longer than an Earth year. It orbits at an average distance of 1.878 AU. Its orbit is mildly elliptical (eccentricity 0.08).
How Was eps Tau b Discovered?
eps Tau b was discovered in 2006 using the radial velocity method, with observations from Okayama Astrophysical 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 eps Tau b?
eps Tau b is 155.0 light-years (47.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1871. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,728,000 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. eps Tau b scores 0.12, ranking #4,349 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: eps Tau
eps Tau
- Spectral type
- K0 III
- Surface temperature
- 4,877 K (Sun: 5,772 K)
- Mass
- 2.57 M☉
- Radius
- 12.35 R☉
- Luminosity
- 78.1106 L☉
Planetary System
eps Tau b is the only planet known to orbit eps Tau so far.
eps Tau b — Complete Data
| Mass (best estimate) | 2,285.19 Earth masses |
|---|---|
| Orbital period | 585.82 days |
| Orbital distance | 1.878 AU |
| Eccentricity | 0.076 |
| Earth Similarity Index | 0.12 |
| Distance from Earth | 155.0 light-years (47.5 parsecs) |
| Constellation | Taurus |
| Discovery method | Radial Velocity |
| Discovery facility | Okayama Astrophysical Observatory |
| Discovery year | 2006 |
Data: NASA Exoplanet Archive, last updated 2023-09-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About eps Tau b
Is eps Tau b habitable?
No — eps Tau b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is eps Tau b?
eps Tau b is about 155 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,728,000 years to get there.
How long is a year on eps Tau b?
One orbit around eps Tau takes 585.8 Earth days.
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