GJ 3473 b
GJ 3473 b is a super-Earth orbiting GJ 3473 in the constellation Canis Minor. It lies about 89 light-years from Earth and was discovered in 2020 using the transit method.
How Big Is GJ 3473 b?
GJ 3473 b has a radius of 1.26 times that of Earth. Its mass is 1.9 times that of Earth, giving it a density of 5.03 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is GJ 3473 b in the Habitable Zone?
GJ 3473 b orbits inside the inner edge of the habitable zone of GJ 3473. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 3473: 0.100–0.262 AU (conservative: 0.127–0.249 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3473 b
The equilibrium temperature of GJ 3473 b is about 773 K (500 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 59.40 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 3473 b — one full orbit around GJ 3473 — lasts just 28.8 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.016 AU — closer to its star than Mercury is to the Sun.
How Was GJ 3473 b Discovered?
GJ 3473 b was discovered in 2020 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is GJ 3473 b?
GJ 3473 b is 89.3 light-years (27.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1937. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,571,680 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 3473 b scores 0.31, ranking #1,130 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 3473
GJ 3473 b belongs to a system of 2 stars; it orbits GJ 3473.
GJ 3473
- Surface temperature
- 3,347 K (Sun: 5,772 K)
- Mass
- 0.36 M☉
- Radius
- 0.36 R☉
- Luminosity
- 0.0150 L☉
The GJ 3473 Planetary System
GJ 3473 b is one of 2 known planets in the GJ 3473 system. Its siblings:
- GJ 3473 c (Super Earth)
GJ 3473 b — Complete Data
| Radius | 1.264 Earth radii (0.113 Jupiter radii) |
|---|---|
| Mass | 1.86 Earth masses (0.006 Jupiter masses) |
| Density | 5.03 g/cm³ (Earth: 5.51) |
| Orbital period | 1.20 days |
| Orbital distance | 0.016 AU |
| Equilibrium temperature | 773 K (500 °C) |
| Stellar irradiation | 59.40× Earth |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 89.3 light-years (27.4 parsecs) |
| Constellation | Canis Minor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2020-10-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3473 b
Is GJ 3473 b habitable?
No — GJ 3473 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 3473 b?
GJ 3473 b is about 89 light-years from Earth in the constellation Canis Minor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,571,680 years to get there.
How big is GJ 3473 b compared to Earth?
GJ 3473 b has 1.26 times the radius of Earth and about 1.9 times its mass.
How long is a year on GJ 3473 b?
One orbit around GJ 3473 takes 1.2 Earth days — short enough that 305 of its years would fit into one Earth year.
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