TOI-3877 b
TOI-3877 b is a hot Jupiter orbiting TOI-3877 in the constellation Ursa Major. It lies about 1,611 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is TOI-3877 b?
TOI-3877 b has a radius of 11.68 times that of Earth, or 1.04 times the radius of Jupiter. Its mass is 99.8 times that of Earth, giving it a density of 0.34 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-3877 b in the Habitable Zone?
TOI-3877 b orbits inside the inner edge of the habitable zone of TOI-3877. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-3877: 1.072–2.529 AU (conservative: 1.358–2.398 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-3877 b
The equilibrium temperature of TOI-3877 b is about 1,445 K (1,172 °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 729 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-3877 b — one full orbit around TOI-3877 — lasts 4.12 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.053 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.22).
How Was TOI-3877 b Discovered?
TOI-3877 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-3877 b?
TOI-3877 b is 1,610.5 light-years (493.8 parsecs) from Earth. Light arriving here tonight left the planet about 1,611 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 28,344,800 years to make the journey.
The Host Star: TOI-3877
TOI-3877
- Surface temperature
- 5,731 K (Sun: 5,772 K)
- Mass
- 1.16 M☉
- Radius
- 1.45 R☉
- Luminosity
- 2.0300 L☉
- Age
- 5.9 billion years (Sun: 4.6)
Planetary System
TOI-3877 b is the only planet known to orbit TOI-3877 so far.
TOI-3877 b — Complete Data
| Radius | 11.680 Earth radii (1.042 Jupiter radii) |
|---|---|
| Mass | 99.80 Earth masses (0.314 Jupiter masses) |
| Density | 0.34 g/cm³ (Earth: 5.51) |
| Orbital period | 4.12 days |
| Orbital distance | 0.053 AU |
| Eccentricity | 0.220 |
| Equilibrium temperature | 1,445 K (1,172 °C) |
| Stellar irradiation | 729.00× Earth |
| Distance from Earth | 1,610.5 light-years (493.8 parsecs) |
| Constellation | Ursa Major |
| 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-3877 b
Is TOI-3877 b habitable?
No — TOI-3877 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-3877 b?
TOI-3877 b is about 1,611 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 28,344,800 years to get there.
How big is TOI-3877 b compared to Earth?
TOI-3877 b has 11.68 times the radius of Earth and about 99.8 times its mass.
How long is a year on TOI-3877 b?
One orbit around TOI-3877 takes 4.1 Earth days — short enough that 89 of its years would fit into one Earth year.
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