alf Ari b
alf Ari b is a cold gas giant orbiting alf Ari in the constellation Aries. It lies about 66 light-years from Earth and was discovered in 2010 using the radial velocity method.
Is alf Ari b in the Habitable Zone?
alf Ari b orbits inside the inner edge of the habitable zone of alf Ari. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of alf Ari: 6.889–16.979 AU (conservative: 8.726–16.097 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 Ari b — one full orbit around alf Ari — lasts 380.8 Earth days, longer than an Earth year. It orbits at an average distance of 1.200 AU. Its orbit is mildly elliptical (eccentricity 0.25).
How Was alf Ari b Discovered?
alf Ari b was discovered in 2010 using the radial velocity method, with observations from Bohyunsan Optical Astronomical 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 alf Ari b?
alf Ari b is 65.9 light-years (20.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1961. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,159,840 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 Ari b scores 0.08, ranking #4,595 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: alf Ari
alf Ari
- Surface temperature
- 4,553 K (Sun: 5,772 K)
- Mass
- 1.50 M☉
- Radius
- 13.90 R☉
Planetary System
alf Ari b is the only planet known to orbit alf Ari so far.
alf Ari b — Complete Data
| Mass (best estimate) | 572.07 Earth masses |
|---|---|
| Orbital period | 380.80 days |
| Orbital distance | 1.200 AU |
| Eccentricity | 0.250 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 65.9 light-years (20.2 parsecs) |
| Constellation | Aries |
| Discovery method | Radial Velocity |
| Discovery facility | Bohyunsan Optical Astronomical Observatory |
| Discovery year | 2010 |
Data: NASA Exoplanet Archive, last updated 2019-01-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About alf Ari b
Is alf Ari b habitable?
No — alf Ari b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is alf Ari b?
alf Ari b is about 66 light-years from Earth in the constellation Aries. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,159,840 years to get there.
How long is a year on alf Ari b?
One orbit around alf Ari takes 380.8 Earth days.
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