TOI-5181 A b
TOI-5181 A b is a hot Jupiter orbiting TOI-5181 A in the constellation Hercules. It lies about 1,566 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is TOI-5181 A b?
TOI-5181 A b has a radius of 13.35 times that of Earth, or 1.19 times the radius of Jupiter. Its mass is 331 times that of Earth, giving it a density of 0.76 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-5181 A b in the Habitable Zone?
TOI-5181 A b orbits inside the inner edge of the habitable zone of TOI-5181 A. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5181 A: 1.250–2.924 AU (conservative: 1.583–2.773 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5181 A b
The equilibrium temperature of TOI-5181 A b is about 1,585 K (1,312 °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 1,053 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-5181 A b — one full orbit around TOI-5181 A — lasts 3.89 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.052 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.15).
How Was TOI-5181 A b Discovered?
TOI-5181 A 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-5181 A b?
TOI-5181 A b is 1,566.1 light-years (480.2 parsecs) from Earth. Light arriving here tonight left the planet about 1,566 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 27,563,360 years to make the journey.
The Host Star: TOI-5181 A
TOI-5181 A b belongs to a system of 2 stars; it orbits TOI-5181 A.
TOI-5181 A
- Surface temperature
- 6,060 K (Sun: 5,772 K)
- Mass
- 1.25 M☉
- Radius
- 1.53 R☉
- Luminosity
- 2.8700 L☉
- Age
- 4.1 billion years (Sun: 4.6)
Planetary System
TOI-5181 A b is the only planet known to orbit TOI-5181 A so far.
TOI-5181 A b — Complete Data
| Radius | 13.350 Earth radii (1.191 Jupiter radii) |
|---|---|
| Mass | 330.54 Earth masses (1.040 Jupiter masses) |
| Density | 0.76 g/cm³ (Earth: 5.51) |
| Orbital period | 3.89 days |
| Orbital distance | 0.052 AU |
| Eccentricity | 0.150 |
| Equilibrium temperature | 1,585 K (1,312 °C) |
| Stellar irradiation | 1,053.00× Earth |
| Distance from Earth | 1,566.1 light-years (480.2 parsecs) |
| Constellation | Hercules |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-07-29. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5181 A b
Is TOI-5181 A b habitable?
No — TOI-5181 A b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5181 A b?
TOI-5181 A b is about 1,566 light-years from Earth in the constellation Hercules. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 27,563,360 years to get there.
How big is TOI-5181 A b compared to Earth?
TOI-5181 A b has 13.35 times the radius of Earth and about 331 times its mass.
How long is a year on TOI-5181 A b?
One orbit around TOI-5181 A takes 3.9 Earth days — short enough that 94 of its years would fit into one Earth year.
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