TOI-5205 b
TOI-5205 b is a hot Jupiter orbiting the M4.0 star TOI-5205 in the constellation Vulpecula. It lies about 282 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-5205 b?
TOI-5205 b has a radius of 11.60 times that of Earth, or 1.03 times the radius of Jupiter. Its mass is 343 times that of Earth, giving it a density of 1.21 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-5205 b in the Habitable Zone?
TOI-5205 b orbits inside the inner edge of the habitable zone of TOI-5205. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5205: 0.114–0.297 AU (conservative: 0.144–0.281 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5205 b
The equilibrium temperature of TOI-5205 b is about 737 K (464 °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 49.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-5205 b — one full orbit around TOI-5205 — lasts just 39.1 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.020 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.020).
How Was TOI-5205 b Discovered?
TOI-5205 b was discovered in 2023 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-5205 b?
TOI-5205 b is 282.0 light-years (86.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1744. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,963,200 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. TOI-5205 b scores 0.10, ranking #4,453 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-5205
TOI-5205
- Spectral type
- M4.0
- Surface temperature
- 3,430 K (Sun: 5,772 K)
- Mass
- 0.39 M☉
- Radius
- 0.39 R☉
- Luminosity
- 0.0194 L☉
Planetary System
TOI-5205 b is the only planet known to orbit TOI-5205 so far.
TOI-5205 b — Complete Data
| Radius | 11.600 Earth radii (1.030 Jupiter radii) |
|---|---|
| Mass | 343.00 Earth masses (1.080 Jupiter masses) |
| Density | 1.21 g/cm³ (Earth: 5.51) |
| Orbital period | 1.63 days |
| Orbital distance | 0.020 AU |
| Eccentricity | 0.020 |
| Equilibrium temperature | 737 K (464 °C) |
| Stellar irradiation | 49.00× Earth |
| Earth Similarity Index | 0.10 |
| Distance from Earth | 282.0 light-years (86.4 parsecs) |
| Constellation | Vulpecula |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-03-15. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5205 b
Is TOI-5205 b habitable?
No — TOI-5205 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5205 b?
TOI-5205 b is about 282 light-years from Earth in the constellation Vulpecula. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,963,200 years to get there.
How big is TOI-5205 b compared to Earth?
TOI-5205 b has 11.60 times the radius of Earth and about 343 times its mass.
How long is a year on TOI-5205 b?
One orbit around TOI-5205 takes 1.6 Earth days — short enough that 224 of its years would fit into one Earth year.
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