TOI-5811 B b
TOI-5811 B b is a hot Jupiter orbiting the K2 IV+ star TOI-5811 B in the constellation Delphinus. It lies about 555 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-5811 B b?
TOI-5811 B b has a radius of 21.97 times that of Earth, or 1.96 times the radius of Jupiter. Its mass is 257 times that of Earth, giving it a density of 0.13 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-5811 B b in the Habitable Zone?
TOI-5811 B b orbits inside the inner edge of the habitable zone of TOI-5811 B. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5811 B: 2.069–5.036 AU (conservative: 2.621–4.774 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5811 B b
The equilibrium temperature of TOI-5811 B b is about 1,530 K (1,257 °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 1,320 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-5811 B b — one full orbit around TOI-5811 B — lasts 6.26 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.073 AU — closer to its star than Mercury is to the Sun.
How Was TOI-5811 B b Discovered?
TOI-5811 B b was discovered in 2026 using the transit method, with observations from Multiple Observatories.
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-5811 B b?
TOI-5811 B b is 554.9 light-years (170.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1472. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 9,766,240 years to make the journey.
The Host Star: TOI-5811 B
TOI-5811 B b belongs to a system of 3 stars; it orbits TOI-5811 B.
TOI-5811 B
- Spectral type
- K2 IV+
- Surface temperature
- 4,840 K (Sun: 5,772 K)
- Mass
- 1.08 M☉
- Radius
- 3.73 R☉
- Luminosity
- 6.8770 L☉
Planetary System
TOI-5811 B b is the only planet known to orbit TOI-5811 B so far.
TOI-5811 B b — Complete Data
| Radius | 21.970 Earth radii (1.960 Jupiter radii) |
|---|---|
| Mass | 257.44 Earth masses (0.810 Jupiter masses) |
| Density | 0.13 g/cm³ (Earth: 5.51) |
| Orbital period | 6.26 days |
| Orbital distance | 0.073 AU |
| Equilibrium temperature | 1,530 K (1,257 °C) |
| Stellar irradiation | 1,320.00× Earth |
| Distance from Earth | 554.9 light-years (170.1 parsecs) |
| Constellation | Delphinus |
| Discovery method | Transit |
| Discovery facility | Multiple Observatories |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-08-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5811 B b
Is TOI-5811 B b habitable?
No — TOI-5811 B b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5811 B b?
TOI-5811 B b is about 555 light-years from Earth in the constellation Delphinus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 9,766,240 years to get there.
How big is TOI-5811 B b compared to Earth?
TOI-5811 B b has 21.97 times the radius of Earth and about 257 times its mass.
How long is a year on TOI-5811 B b?
One orbit around TOI-5811 B takes 6.3 Earth days — short enough that 58 of its years would fit into one Earth year.
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