TOI-5120 b
TOI-5120 b is a cold gas giant orbiting TOI-5120 in the constellation Gemini. It lies about 750 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-5120 b?
TOI-5120 b has a radius of 10.86 times that of Earth, or 0.97 times the radius of Jupiter. Its mass is 391 times that of Earth.
Is TOI-5120 b in the Habitable Zone?
TOI-5120 b orbits inside the inner edge of the habitable zone of TOI-5120. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5120: 1.061–2.501 AU (conservative: 1.344–2.371 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5120 b
The equilibrium temperature of TOI-5120 b is about 796 K (523 °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 66.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-5120 b — one full orbit around TOI-5120 — lasts 24.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.172 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.10).
How Was TOI-5120 b Discovered?
TOI-5120 b was discovered in 2026 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-5120 b?
TOI-5120 b is 750.0 light-years (230.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1276. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 13,200,000 years to make the journey.
The Host Star: TOI-5120
TOI-5120
- Surface temperature
- 5,763 K (Sun: 5,772 K)
- Mass
- 1.12 M☉
- Radius
- 1.42 R☉
- Age
- 7.5 billion years (Sun: 4.6)
Planetary System
TOI-5120 b is the only planet known to orbit TOI-5120 so far.
TOI-5120 b — Complete Data
| Radius | 10.862 Earth radii (0.969 Jupiter radii) |
|---|---|
| Mass | 390.93 Earth masses (1.230 Jupiter masses) |
| Orbital period | 24.92 days |
| Orbital distance | 0.172 AU |
| Eccentricity | 0.100 |
| Equilibrium temperature | 796 K (523 °C) |
| Stellar irradiation | 66.00× Earth |
| Distance from Earth | 750.0 light-years (230.0 parsecs) |
| Constellation | Gemini |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-10-15. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5120 b
Is TOI-5120 b habitable?
No — TOI-5120 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5120 b?
TOI-5120 b is about 750 light-years from Earth in the constellation Gemini. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 13,200,000 years to get there.
How big is TOI-5120 b compared to Earth?
TOI-5120 b has 10.86 times the radius of Earth and about 391 times its mass.
How long is a year on TOI-5120 b?
One orbit around TOI-5120 takes 24.9 Earth days — short enough that 15 of its years would fit into one Earth year.
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