TOI-789 c
TOI-789 c is a terrestrial planet orbiting the M3 V star TOI-789 in the constellation Volans. It lies about 142 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-789 c?
TOI-789 c has a radius of 1.15 times that of Earth. Its mass is 3.0 times that of Earth.
Is TOI-789 c in the Habitable Zone?
TOI-789 c orbits inside the inner edge of the habitable zone of TOI-789. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-789: 0.110–0.285 AU (conservative: 0.139–0.270 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-789 c
The equilibrium temperature of TOI-789 c is about 394 K (121 °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 5.70 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-789 c — one full orbit around TOI-789 — lasts 8.04 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.056 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.05).
How Was TOI-789 c Discovered?
TOI-789 c was discovered in 2026 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-789 c?
TOI-789 c is 141.6 light-years (43.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1885. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,492,160 years to make the journey.
The Host Star: TOI-789
TOI-789
- Spectral type
- M3 V
- Surface temperature
- 3,471 K (Sun: 5,772 K)
- Mass
- 0.36 M☉
- Radius
- 0.37 R☉
The TOI-789 Planetary System
TOI-789 c is one of 3 known planets in the TOI-789 system. Its siblings:
TOI-789 c — Complete Data
| Radius | 1.150 Earth radii (0.103 Jupiter radii) |
|---|---|
| Mass | 3.00 Earth masses (0.009 Jupiter masses) |
| Orbital period | 8.04 days |
| Orbital distance | 0.056 AU |
| Eccentricity | 0.050 |
| Equilibrium temperature | 394 K (121 °C) |
| Stellar irradiation | 5.70× Earth |
| Distance from Earth | 141.6 light-years (43.4 parsecs) |
| Constellation | Volans |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-10-08. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-789 c
Is TOI-789 c habitable?
No — TOI-789 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-789 c?
TOI-789 c is about 142 light-years from Earth in the constellation Volans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,492,160 years to get there.
How big is TOI-789 c compared to Earth?
TOI-789 c has 1.15 times the radius of Earth and about 3.0 times its mass.
How long is a year on TOI-789 c?
One orbit around TOI-789 takes 8.0 Earth days — short enough that 45 of its years would fit into one Earth year.
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