TOI-5573 b
TOI-5573 b is a hot Jupiter orbiting TOI-5573 in the constellation Ursa Major. It lies about 609 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is TOI-5573 b?
TOI-5573 b has a radius of 9.75 times that of Earth, or 0.87 times the radius of Jupiter. Its mass is 112 times that of Earth, giving it a density of 0.66 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-5573 b in the Habitable Zone?
TOI-5573 b orbits inside the inner edge of the habitable zone of TOI-5573. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5573: 0.214–0.548 AU (conservative: 0.272–0.520 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5573 b
The equilibrium temperature of TOI-5573 b is about 528 K (255 °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 12.92 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-5573 b — one full orbit around TOI-5573 — lasts 8.80 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.071 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.07).
How Was TOI-5573 b Discovered?
TOI-5573 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-5573 b?
TOI-5573 b is 608.5 light-years (186.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1418. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 10,709,600 years to make the journey.
The Host Star: TOI-5573
TOI-5573
- Surface temperature
- 3,790 K (Sun: 5,772 K)
- Mass
- 0.62 M☉
- Radius
- 0.59 R☉
- Luminosity
- 0.0693 L☉
- Age
- 9.7 billion years (Sun: 4.6)
Planetary System
TOI-5573 b is the only planet known to orbit TOI-5573 so far.
TOI-5573 b — Complete Data
| Radius | 9.750 Earth radii (0.870 Jupiter radii) |
|---|---|
| Mass | 112.00 Earth masses (0.350 Jupiter masses) |
| Density | 0.66 g/cm³ (Earth: 5.51) |
| Orbital period | 8.80 days |
| Orbital distance | 0.071 AU |
| Eccentricity | 0.072 |
| Equilibrium temperature | 528 K (255 °C) |
| Stellar irradiation | 12.92× Earth |
| Distance from Earth | 608.5 light-years (186.6 parsecs) |
| Constellation | Ursa Major |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-05-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5573 b
Is TOI-5573 b habitable?
No — TOI-5573 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5573 b?
TOI-5573 b is about 609 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 10,709,600 years to get there.
How big is TOI-5573 b compared to Earth?
TOI-5573 b has 9.75 times the radius of Earth and about 112 times its mass.
How long is a year on TOI-5573 b?
One orbit around TOI-5573 takes 8.8 Earth days — short enough that 42 of its years would fit into one Earth year.
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