TOI-7166 b
TOI-7166 b is a mini-Neptune orbiting the M4.5+/-0.5 star TOI-7166 in the constellation Equuleus. It lies about 116 light-years from Earth and was discovered in 2025 using the transit method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
How Big Is TOI-7166 b?
TOI-7166 b has a radius of 2.01 times that of Earth.
Is TOI-7166 b in the Habitable Zone?
TOI-7166 b orbits within the optimistic habitable zone of TOI-7166 — the broader region where liquid water might be possible under favorable atmospheric conditions.
Habitable zone of TOI-7166: 0.053–0.139 AU (conservative: 0.067–0.132 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-7166 b
The equilibrium temperature of TOI-7166 b is about 249 K (-24 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 1.07 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-7166 b — one full orbit around TOI-7166 — lasts 12.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.062 AU — closer to its star than Mercury is to the Sun.
How Was TOI-7166 b Discovered?
TOI-7166 b was discovered in 2025 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-7166 b?
TOI-7166 b is 115.5 light-years (35.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1911. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,032,800 years to make the journey.
The Host Star: TOI-7166
TOI-7166
- Spectral type
- M4.5+/-0.5
- Surface temperature
- 3,099 K (Sun: 5,772 K)
- Mass
- 0.19 M☉
- Radius
- 0.22 R☉
- Luminosity
- 0.0041 L☉
- Age
- 4.0 billion years (Sun: 4.6)
Planetary System
TOI-7166 b is the only planet known to orbit TOI-7166 so far.
TOI-7166 b — Complete Data
| Radius | 2.010 Earth radii (0.179 Jupiter radii) |
|---|---|
| Orbital period | 12.92 days |
| Orbital distance | 0.062 AU |
| Equilibrium temperature | 249 K (-24 °C) |
| Stellar irradiation | 1.07× Earth |
| Distance from Earth | 115.5 light-years (35.4 parsecs) |
| Constellation | Equuleus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2026-01-15. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-7166 b
Is TOI-7166 b habitable?
TOI-7166 b orbits within the habitable zone of TOI-7166, 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 TOI-7166 b?
TOI-7166 b is about 116 light-years from Earth in the constellation Equuleus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,032,800 years to get there.
How big is TOI-7166 b compared to Earth?
TOI-7166 b has 2.01 times the radius of Earth.
How long is a year on TOI-7166 b?
One orbit around TOI-7166 takes 12.9 Earth days — short enough that 28 of its years would fit into one Earth year.
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