TOI-4438 b
TOI-4438 b is a mini-Neptune orbiting the M3.5 V star TOI-4438 in the constellation Hercules. It lies about 98 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-4438 b?
TOI-4438 b has a radius of 2.52 times that of Earth. Its mass is 5.4 times that of Earth, giving it a density of 1.85 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-4438 b in the Habitable Zone?
TOI-4438 b orbits inside the inner edge of the habitable zone of TOI-4438. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-4438: 0.107–0.279 AU (conservative: 0.135–0.264 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-4438 b
The equilibrium temperature of TOI-4438 b is about 435 K (162 °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 6.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-4438 b — one full orbit around TOI-4438 — lasts 7.45 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.053 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.14).
How Was TOI-4438 b Discovered?
TOI-4438 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-4438 b?
TOI-4438 b is 98.0 light-years (30.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1928. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,724,800 years to make the journey.
The Host Star: TOI-4438
TOI-4438
- Spectral type
- M3.5 V
- Surface temperature
- 3,422 K (Sun: 5,772 K)
- Mass
- 0.37 M☉
- Radius
- 0.37 R☉
- Luminosity
- 0.0171 L☉
- Age
- 5.1 billion years (Sun: 4.6)
Planetary System
TOI-4438 b is the only planet known to orbit TOI-4438 so far.
TOI-4438 b — Complete Data
| Radius | 2.520 Earth radii (0.225 Jupiter radii) |
|---|---|
| Mass | 5.40 Earth masses (0.017 Jupiter masses) |
| Density | 1.85 g/cm³ (Earth: 5.51) |
| Orbital period | 7.45 days |
| Orbital distance | 0.053 AU |
| Eccentricity | 0.140 |
| Equilibrium temperature | 435 K (162 °C) |
| Stellar irradiation | 6.00× Earth |
| Distance from Earth | 98.0 light-years (30.0 parsecs) |
| Constellation | Hercules |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-03-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-4438 b
Is TOI-4438 b habitable?
No — TOI-4438 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-4438 b?
TOI-4438 b is about 98 light-years from Earth in the constellation Hercules. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,724,800 years to get there.
How big is TOI-4438 b compared to Earth?
TOI-4438 b has 2.52 times the radius of Earth and about 5.4 times its mass.
How long is a year on TOI-4438 b?
One orbit around TOI-4438 takes 7.4 Earth days — short enough that 49 of its years would fit into one Earth year.
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