TOI-238 b
TOI-238 b is a super-Earth orbiting the K2 V star TOI-238 in the constellation Aquarius. It lies about 263 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-238 b?
TOI-238 b has a radius of 1.56 times that of Earth. Its mass is 3.4 times that of Earth.
Is TOI-238 b in the Habitable Zone?
TOI-238 b orbits inside the inner edge of the habitable zone of TOI-238. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-238: 0.453–1.092 AU (conservative: 0.573–1.035 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-238 b
The equilibrium temperature of TOI-238 b is about 1,378 K (1,105 °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 753 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-238 b — one full orbit around TOI-238 — lasts just 30.6 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.021 AU — closer to its star than Mercury is to the Sun.
How Was TOI-238 b Discovered?
TOI-238 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-238 b?
TOI-238 b is 262.7 light-years (80.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1764. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,623,520 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. TOI-238 b scores 0.28, ranking #2,084 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-238
TOI-238
- Spectral type
- K2 V
- Surface temperature
- 5,059 K (Sun: 5,772 K)
- Mass
- 0.78 M☉
- Radius
- 0.76 R☉
- Age
- 7.9 billion years (Sun: 4.6)
The TOI-238 Planetary System
TOI-238 b is one of 2 known planets in the TOI-238 system. Its siblings:
- TOI-238 c (Mini Neptune)
TOI-238 b — Complete Data
| Radius | 1.559 Earth radii (0.139 Jupiter radii) |
|---|---|
| Mass | 3.37 Earth masses (0.011 Jupiter masses) |
| Orbital period | 1.27 days |
| Orbital distance | 0.021 AU |
| Equilibrium temperature | 1,378 K (1,105 °C) |
| Stellar irradiation | 753.10× Earth |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 262.7 light-years (80.5 parsecs) |
| Constellation | Aquarius |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2025-11-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-238 b
Is TOI-238 b habitable?
No — TOI-238 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-238 b?
TOI-238 b is about 263 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,623,520 years to get there.
How big is TOI-238 b compared to Earth?
TOI-238 b has 1.56 times the radius of Earth and about 3.4 times its mass.
How long is a year on TOI-238 b?
One orbit around TOI-238 takes 1.3 Earth days — short enough that 287 of its years would fit into one Earth year.
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