47 UMa b
47 UMa b is a cold gas giant orbiting 47 UMa in the constellation Ursa Major. It lies about 45 light-years from Earth and was discovered in 1996 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is 47 UMa b in the Habitable Zone?
47 UMa b orbits within the optimistic habitable zone of 47 UMa — the broader region where liquid water might be possible under favorable atmospheric conditions.
Habitable zone of 47 UMa: 0.937–2.202 AU (conservative: 1.187–2.088 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 47 UMa b — one full orbit around 47 UMa — lasts 1,078.0 Earth days, longer than an Earth year. It orbits at an average distance of 2.100 AU. Its orbit is nearly circular (eccentricity 0.032).
How Was 47 UMa b Discovered?
47 UMa 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 47 UMa b?
47 UMa b is 45.0 light-years (13.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1981. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 792,000 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. 47 UMa b scores 0.31, ranking #1,212 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: 47 UMa
47 UMa
- Surface temperature
- 5,872 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 1.21 R☉
- Luminosity
- 1.5769 L☉
The 47 UMa Planetary System
47 UMa b is one of 3 known planets in the 47 UMa system. Its siblings:
47 UMa b — Complete Data
| Mass (best estimate) | 804.08 Earth masses |
|---|---|
| Orbital period | 1,078.00 days |
| Orbital distance | 2.100 AU |
| Eccentricity | 0.032 |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 45.0 light-years (13.8 parsecs) |
| Constellation | Ursa Major |
| Discovery method | Radial Velocity |
| Discovery facility | Lick Observatory |
| Discovery year | 1996 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About 47 UMa b
Is 47 UMa b habitable?
47 UMa b orbits within the habitable zone of 47 UMa, the region where liquid water could exist on a planet's surface. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is 47 UMa b?
47 UMa b is about 45 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 792,000 years to get there.
How long is a year on 47 UMa b?
One orbit around 47 UMa takes 1,078.0 Earth days.
Explore 47 UMa b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
