TOI-2120 b
TOI-2120 b is a super-Earth orbiting TOI-2120 in the constellation Cassiopeia. It lies about 105 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-2120 b?
TOI-2120 b has a radius of 2.12 times that of Earth. Its mass is 6.8 times that of Earth.
Is TOI-2120 b in the Habitable Zone?
TOI-2120 b orbits inside the inner edge of the habitable zone of TOI-2120. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-2120: 0.059–0.156 AU (conservative: 0.075–0.148 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-2120 b
The equilibrium temperature of TOI-2120 b is about 384 K (111 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 3.61 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-2120 b — one full orbit around TOI-2120 — lasts 5.80 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.038 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.32), swinging dramatically closer to and farther from its star.
How Was TOI-2120 b Discovered?
TOI-2120 b was discovered in 2024 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 TOI-2120 b?
TOI-2120 b is 104.9 light-years (32.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1922. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,846,240 years to make the journey.
The Host Star: TOI-2120
TOI-2120
- Surface temperature
- 3,131 K (Sun: 5,772 K)
- Mass
- 0.21 M☉
- Radius
- 0.25 R☉
- Luminosity
- 0.0052 L☉
Planetary System
TOI-2120 b is the only planet known to orbit TOI-2120 so far.
TOI-2120 b — Complete Data
| Radius | 2.122 Earth radii (0.189 Jupiter radii) |
|---|---|
| Mass | 6.80 Earth masses (0.021 Jupiter masses) |
| Orbital period | 5.80 days |
| Orbital distance | 0.038 AU |
| Eccentricity | 0.320 |
| Equilibrium temperature | 384 K (111 °C) |
| Stellar irradiation | 3.61× Earth |
| Distance from Earth | 104.9 light-years (32.2 parsecs) |
| Constellation | Cassiopeia |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2025-12-18. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-2120 b
Is TOI-2120 b habitable?
No — TOI-2120 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-2120 b?
TOI-2120 b is about 105 light-years from Earth in the constellation Cassiopeia. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,846,240 years to get there.
How big is TOI-2120 b compared to Earth?
TOI-2120 b has 2.12 times the radius of Earth and about 6.8 times its mass.
How long is a year on TOI-2120 b?
One orbit around TOI-2120 takes 5.8 Earth days — short enough that 63 of its years would fit into one Earth year.
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