TOI-128.01
TOI-128.01 is a mini-Neptune orbiting TOI-128 in the constellation Mensa. It lies about 223 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-128.01?
TOI-128.01 has a radius of 2.22 times that of Earth.
Is TOI-128.01 in the Habitable Zone?
TOI-128.01 orbits inside the inner edge of the habitable zone of TOI-128. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-128: 0.923–2.159 AU (conservative: 1.170–2.047 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on TOI-128.01
The equilibrium temperature of TOI-128.01 is about 1,345 K (1,071 °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 182 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-128.01 — one full orbit around TOI-128 — lasts 4.94 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.054 AU — closer to its star than Mercury is to the Sun.
How Was TOI-128.01 Discovered?
TOI-128.01 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-128.01?
TOI-128.01 is 223.3 light-years (68.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1803. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,930,080 years to make the journey.
The Host Star: TOI-128
TOI-128
- Surface temperature
- 6,086 K (Sun: 5,772 K)
- Mass
- 0.85 M☉
- Radius
- 1.13 R☉
Planetary System
TOI-128.01 is the only planet known to orbit TOI-128 so far.
TOI-128.01 — Complete Data
| Radius | 2.219 Earth radii (0.198 Jupiter radii) |
|---|---|
| Orbital period | 4.94 days |
| Orbital distance | 0.054 AU |
| Equilibrium temperature | 1,345 K (1,071 °C) |
| Stellar irradiation | 182.41× Earth |
| Distance from Earth | 223.3 light-years (68.5 parsecs) |
| Constellation | Mensa |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-06-11. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-128.01
Is TOI-128.01 habitable?
No — TOI-128.01 orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-128.01?
TOI-128.01 is about 223 light-years from Earth in the constellation Mensa. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,930,080 years to get there.
How big is TOI-128.01 compared to Earth?
TOI-128.01 has 2.22 times the radius of Earth.
How long is a year on TOI-128.01?
One orbit around TOI-128 takes 4.9 Earth days — short enough that 74 of its years would fit into one Earth year.
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