TOI-1243 b
TOI-1243 b is a super-Earth orbiting the M2.0 V star TOI-1243 in the constellation Ursa Major. It lies about 141 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-1243 b?
TOI-1243 b has a radius of 2.33 times that of Earth. Its mass is 7.7 times that of Earth, giving it a density of 3.30 g/cm³ — between that of rocky and gaseous planets.
Is TOI-1243 b in the Habitable Zone?
The position of TOI-1243 b relative to the habitable zone of TOI-1243 cannot be precisely determined from the available orbital data.
Habitable zone of TOI-1243: 0.155–0.401 AU (conservative: 0.196–0.381 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-1243 b
The equilibrium temperature of TOI-1243 b is about 450 K (177 °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.
Orbit and Year Length
A year on TOI-1243 b — one full orbit around TOI-1243 — lasts 4.66 Earth days, shorter than Mercury's 88-day year.
How Was TOI-1243 b Discovered?
TOI-1243 b was discovered in 2026 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-1243 b?
TOI-1243 b is 140.9 light-years (43.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1886. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,479,840 years to make the journey.
The Host Star: TOI-1243
TOI-1243
- Spectral type
- M2.0 V
- Surface temperature
- 3,515 K (Sun: 5,772 K)
- Mass
- 0.52 M☉
- Radius
- 0.51 R☉
- Luminosity
- 0.0359 L☉
Planetary System
TOI-1243 b is the only planet known to orbit TOI-1243 so far.
TOI-1243 b — Complete Data
| Radius | 2.330 Earth radii (0.208 Jupiter radii) |
|---|---|
| Mass | 7.70 Earth masses (0.024 Jupiter masses) |
| Density | 3.30 g/cm³ (Earth: 5.51) |
| Orbital period | 4.66 days |
| Equilibrium temperature | 450 K (177 °C) |
| Distance from Earth | 140.9 light-years (43.2 parsecs) |
| Constellation | Ursa Major |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-02-05. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1243 b
Is TOI-1243 b habitable?
TOI-1243 b is not known to orbit within the habitable zone of TOI-1243, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is TOI-1243 b?
TOI-1243 b is about 141 light-years from Earth in the constellation Ursa Major. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,479,840 years to get there.
How big is TOI-1243 b compared to Earth?
TOI-1243 b has 2.33 times the radius of Earth and about 7.7 times its mass.
How long is a year on TOI-1243 b?
One orbit around TOI-1243 takes 4.7 Earth days — short enough that 78 of its years would fit into one Earth year.
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