TOI-1273 b
TOI-1273 b is a hot Jupiter orbiting TOI-1273 in the constellation Ursa Major. It lies about 578 light-years from Earth and was discovered in 2024 using the transit method.
How Big Is TOI-1273 b?
TOI-1273 b has a radius of 11.10 times that of Earth, or 0.99 times the radius of Jupiter. Its mass is 70.6 times that of Earth, giving it a density of 0.28 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-1273 b in the Habitable Zone?
TOI-1273 b orbits inside the inner edge of the habitable zone of TOI-1273. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1273: 0.780–1.843 AU (conservative: 0.988–1.747 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on TOI-1273 b
The equilibrium temperature of TOI-1273 b is about 1,211 K (938 °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.
Orbit and Year Length
A year on TOI-1273 b — one full orbit around TOI-1273 — lasts 4.63 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.055 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.06).
How Was TOI-1273 b Discovered?
TOI-1273 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-1273 b?
TOI-1273 b is 577.7 light-years (177.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1449. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 10,167,520 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-1273 b scores 0.08, ranking #4,623 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-1273
TOI-1273
- Surface temperature
- 5,690 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 1.06 R☉
- Luminosity
- 1.0700 L☉
- Age
- 3.1 billion years (Sun: 4.6)
Planetary System
TOI-1273 b is the only planet known to orbit TOI-1273 so far.
TOI-1273 b — Complete Data
| Radius | 11.097 Earth radii (0.990 Jupiter radii) |
|---|---|
| Mass | 70.56 Earth masses (0.222 Jupiter masses) |
| Density | 0.28 g/cm³ (Earth: 5.51) |
| Orbital period | 4.63 days |
| Orbital distance | 0.055 AU |
| Eccentricity | 0.055 |
| Equilibrium temperature | 1,211 K (938 °C) |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 577.7 light-years (177.1 parsecs) |
| Constellation | Ursa Major |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-03-05. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1273 b
Is TOI-1273 b habitable?
No — TOI-1273 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1273 b?
TOI-1273 b is about 578 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 10,167,520 years to get there.
How big is TOI-1273 b compared to Earth?
TOI-1273 b has 11.10 times the radius of Earth and about 70.6 times its mass.
How long is a year on TOI-1273 b?
One orbit around TOI-1273 takes 4.6 Earth days — short enough that 79 of its years would fit into one Earth year.
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