GJ 273 b
GJ 273 b is a super-Earth orbiting the M3.5 star GJ 273 in the constellation Canis Minor. It lies about 19 light-years from Earth and was discovered in 2017 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 GJ 273 b in the Habitable Zone?
GJ 273 b orbits within the optimistic habitable zone of GJ 273 — the broader region where liquid water might be possible under favorable atmospheric conditions.
Habitable zone of GJ 273: 0.077–0.201 AU (conservative: 0.097–0.190 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 273 b
GJ 273 b receives 1.06 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 273 b — one full orbit around GJ 273 — lasts 18.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.091 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.10).
How Was GJ 273 b Discovered?
GJ 273 b was discovered in 2017 using the radial velocity method, with observations from La Silla 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 GJ 273 b?
GJ 273 b is 19.3 light-years (5.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 2007. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 339,680 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. GJ 273 b scores 0.85, ranking #13 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 273
GJ 273
- Spectral type
- M3.5
- Surface temperature
- 3,382 K (Sun: 5,772 K)
- Mass
- 0.29 M☉
- Radius
- 0.29 R☉
- Luminosity
- 0.0088 L☉
The GJ 273 Planetary System
GJ 273 b is one of 2 known planets in the GJ 273 system. Its siblings:
- GJ 273 c (Terrestrial)
GJ 273 b — Complete Data
| Mass (best estimate) | 2.89 Earth masses |
|---|---|
| Orbital period | 18.65 days |
| Orbital distance | 0.091 AU |
| Eccentricity | 0.100 |
| Stellar irradiation | 1.06× Earth |
| Earth Similarity Index | 0.85 |
| Distance from Earth | 19.3 light-years (5.9 parsecs) |
| Constellation | Canis Minor |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2017-03-29. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 273 b
Is GJ 273 b habitable?
GJ 273 b orbits within the habitable zone of GJ 273, 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 GJ 273 b?
GJ 273 b is about 19 light-years from Earth in the constellation Canis Minor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 339,680 years to get there.
How long is a year on GJ 273 b?
One orbit around GJ 273 takes 18.6 Earth days — short enough that 20 of its years would fit into one Earth year.
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