TOI-791 b
TOI-791 b is a cold gas giant orbiting the F7 star TOI-791 in the constellation Volans. It lies about 1,113 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-791 b?
TOI-791 b has a radius of 11.13 times that of Earth, or 0.99 times the radius of Jupiter. Its mass is 9.5 times that of Earth, giving it a density of 0.04 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-791 b in the Habitable Zone?
TOI-791 b orbits inside the inner edge of the habitable zone of TOI-791. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-791: 1.272–2.963 AU (conservative: 1.611–2.809 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-791 b
The equilibrium temperature of TOI-791 b is about 434 K (161 °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 8.47 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-791 b — one full orbit around TOI-791 — lasts 139.3 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.602 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.032).
How Was TOI-791 b Discovered?
TOI-791 b 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-791 b?
TOI-791 b is 1,112.9 light-years (341.2 parsecs) from Earth. Light arriving here tonight left the planet about 1,113 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 19,587,040 years to make the journey.
The Host Star: TOI-791
TOI-791
- Spectral type
- F7
- Surface temperature
- 6,294 K (Sun: 5,772 K)
- Mass
- 1.28 M☉
- Radius
- 1.47 R☉
The TOI-791 Planetary System
TOI-791 b is one of 2 known planets in the TOI-791 system. Its siblings:
- TOI-791 c (Cold Gas Giant)
TOI-791 b — Complete Data
| Radius | 11.131 Earth radii (0.993 Jupiter radii) |
|---|---|
| Mass | 9.50 Earth masses (0.030 Jupiter masses) |
| Density | 0.04 g/cm³ (Earth: 5.51) |
| Orbital period | 139.30 days |
| Orbital distance | 0.602 AU |
| Eccentricity | 0.032 |
| Equilibrium temperature | 434 K (161 °C) |
| Stellar irradiation | 8.47× Earth |
| Distance from Earth | 1,112.9 light-years (341.2 parsecs) |
| Constellation | Volans |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-07-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-791 b
Is TOI-791 b habitable?
No — TOI-791 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-791 b?
TOI-791 b is about 1,113 light-years from Earth in the constellation Volans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 19,587,040 years to get there.
How big is TOI-791 b compared to Earth?
TOI-791 b has 11.13 times the radius of Earth and about 9.5 times its mass.
How long is a year on TOI-791 b?
One orbit around TOI-791 takes 139.3 Earth days.
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