TOI-1438 b
TOI-1438 b is a sub-Neptune orbiting the K0 V star TOI-1438 in the constellation Draco. It lies about 360 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is TOI-1438 b?
TOI-1438 b has a radius of 3.04 times that of Earth. Its mass is 9.4 times that of Earth, giving it a density of 1.80 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-1438 b in the Habitable Zone?
TOI-1438 b orbits inside the inner edge of the habitable zone of TOI-1438. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1438: 0.519–1.245 AU (conservative: 0.658–1.180 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-1438 b
The equilibrium temperature of TOI-1438 b is about 971 K (698 °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 145 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-1438 b — one full orbit around TOI-1438 — lasts 5.14 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.055 AU — closer to its star than Mercury is to the Sun.
How Was TOI-1438 b Discovered?
TOI-1438 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-1438 b?
TOI-1438 b is 360.4 light-years (110.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1666. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,343,040 years to make the journey.
The Host Star: TOI-1438
TOI-1438
- Spectral type
- K0 V
- Surface temperature
- 5,230 K (Sun: 5,772 K)
- Mass
- 0.88 M☉
- Radius
- 0.82 R☉
- Luminosity
- 0.4500 L☉
The TOI-1438 Planetary System
TOI-1438 b is one of 2 known planets in the TOI-1438 system. Its siblings:
- TOI-1438 c (Mini Neptune)
TOI-1438 b — Complete Data
| Radius | 3.040 Earth radii (0.271 Jupiter radii) |
|---|---|
| Mass | 9.40 Earth masses (0.030 Jupiter masses) |
| Density | 1.80 g/cm³ (Earth: 5.51) |
| Orbital period | 5.14 days |
| Orbital distance | 0.055 AU |
| Equilibrium temperature | 971 K (698 °C) |
| Stellar irradiation | 145.00× Earth |
| Distance from Earth | 360.4 light-years (110.5 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1438 b
Is TOI-1438 b habitable?
No — TOI-1438 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1438 b?
TOI-1438 b is about 360 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,343,040 years to get there.
How big is TOI-1438 b compared to Earth?
TOI-1438 b has 3.04 times the radius of Earth and about 9.4 times its mass.
How long is a year on TOI-1438 b?
One orbit around TOI-1438 takes 5.1 Earth days — short enough that 71 of its years would fit into one Earth year.
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