TOI-1173 b
TOI-1173 b is a hot Jupiter orbiting the G9 star TOI-1173 in the constellation Ursa Minor. It lies about 432 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-1173 b?
TOI-1173 b has a radius of 9.19 times that of Earth, or 0.82 times the radius of Jupiter. Its mass is 27.4 times that of Earth, giving it a density of 0.20 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-1173 b in the Habitable Zone?
TOI-1173 b orbits inside the inner edge of the habitable zone of TOI-1173. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1173: 0.616–1.470 AU (conservative: 0.780–1.394 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-1173 b
The equilibrium temperature of TOI-1173 b is about 868 K (595 °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 132 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-1173 b — one full orbit around TOI-1173 — lasts 7.06 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.070 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.023).
How Was TOI-1173 b Discovered?
TOI-1173 b was discovered in 2024 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-1173 b?
TOI-1173 b is 431.7 light-years (132.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1595. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 7,597,920 years to make the journey.
The Host Star: TOI-1173
TOI-1173 b belongs to a system of 2 stars; it orbits TOI-1173.
TOI-1173
- Spectral type
- G9
- Surface temperature
- 5,350 K (Sun: 5,772 K)
- Mass
- 0.91 M☉
- Radius
- 0.93 R☉
- Age
- 8.7 billion years (Sun: 4.6)
Planetary System
TOI-1173 b is the only planet known to orbit TOI-1173 so far.
TOI-1173 b — Complete Data
| Radius | 9.190 Earth radii (0.820 Jupiter radii) |
|---|---|
| Mass | 27.40 Earth masses (0.086 Jupiter masses) |
| Density | 0.20 g/cm³ (Earth: 5.51) |
| Orbital period | 7.06 days |
| Orbital distance | 0.070 AU |
| Eccentricity | 0.023 |
| Equilibrium temperature | 868 K (595 °C) |
| Stellar irradiation | 132.00× Earth |
| Distance from Earth | 431.7 light-years (132.4 parsecs) |
| Constellation | Ursa Minor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-08-07. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1173 b
Is TOI-1173 b habitable?
No — TOI-1173 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1173 b?
TOI-1173 b is about 432 light-years from Earth in the constellation Ursa Minor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 7,597,920 years to get there.
How big is TOI-1173 b compared to Earth?
TOI-1173 b has 9.19 times the radius of Earth and about 27.4 times its mass.
How long is a year on TOI-1173 b?
One orbit around TOI-1173 takes 7.1 Earth days — short enough that 52 of its years would fit into one Earth year.
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