alf Tau b
The parameters of this planet are disputed or ambiguous in the scientific literature.
alf Tau b is a cold gas giant orbiting the K5 III star alf Tau in the constellation Taurus. It lies about 67 light-years from Earth and was discovered in 2015 using the radial velocity method.
Is alf Tau b in the Habitable Zone?
alf Tau b orbits inside the inner edge of the habitable zone of alf Tau. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of alf Tau: 17.994–45.420 AU (conservative: 22.792–43.062 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 alf Tau b — one full orbit around alf Tau — lasts 629.0 Earth days, longer than an Earth year. It orbits at an average distance of 1.460 AU. Its orbit is mildly elliptical (eccentricity 0.10).
How Was alf Tau b Discovered?
alf Tau b was discovered in 2015 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 alf Tau b?
alf Tau b is 66.6 light-years (20.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1960. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,172,160 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. alf Tau b scores 0.07, ranking #4,791 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: alf Tau
alf Tau b belongs to a system of 2 stars; it orbits alf Tau.
alf Tau
- Spectral type
- K5 III
- Surface temperature
- 4,055 K (Sun: 5,772 K)
- Mass
- 1.13 M☉
- Radius
- 45.10 R☉
- Age
- 6.6 billion years (Sun: 4.6)
Planetary System
alf Tau b is the only planet known to orbit alf Tau so far.
alf Tau b — Complete Data
| Mass (best estimate) | 2,056.36 Earth masses |
|---|---|
| Orbital period | 628.96 days |
| Orbital distance | 1.460 AU |
| Eccentricity | 0.100 |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 66.6 light-years (20.4 parsecs) |
| Constellation | Taurus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2015 |
Data: NASA Exoplanet Archive, last updated 2015-06-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About alf Tau b
Is alf Tau b habitable?
No — alf Tau b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is alf Tau b?
alf Tau b is about 67 light-years from Earth in the constellation Taurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,172,160 years to get there.
How long is a year on alf Tau b?
One orbit around alf Tau takes 629.0 Earth days.
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