TOI-209 b
TOI-209 b is a mini-Neptune orbiting TOI-209 in the constellation Tucana. It lies about 370 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is TOI-209 b?
TOI-209 b has a radius of 2.39 times that of Earth.
Is TOI-209 b in the Habitable Zone?
The position of TOI-209 b relative to the habitable zone of TOI-209 cannot be precisely determined from the available orbital data.
Habitable zone of TOI-209: 0.406–0.990 AU (conservative: 0.514–0.939 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 ›
Orbit and Year Length
A year on TOI-209 b — one full orbit around TOI-209 — lasts 4.38 Earth days, shorter than Mercury's 88-day year.
How Was TOI-209 b Discovered?
TOI-209 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-209 b?
TOI-209 b is 369.8 light-years (113.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1657. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,508,480 years to make the journey.
The Host Star: TOI-209
TOI-209
- Surface temperature
- 4,807 K (Sun: 5,772 K)
- Radius
- 0.74 R☉
Planetary System
TOI-209 b is the only planet known to orbit TOI-209 so far.
TOI-209 b — Complete Data
| Radius | 2.395 Earth radii (0.214 Jupiter radii) |
|---|---|
| Orbital period | 4.38 days |
| Distance from Earth | 369.8 light-years (113.4 parsecs) |
| Constellation | Tucana |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-04-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-209 b
Is TOI-209 b habitable?
TOI-209 b is not known to orbit within the habitable zone of TOI-209, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is TOI-209 b?
TOI-209 b is about 370 light-years from Earth in the constellation Tucana. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,508,480 years to get there.
How big is TOI-209 b compared to Earth?
TOI-209 b has 2.39 times the radius of Earth.
How long is a year on TOI-209 b?
One orbit around TOI-209 takes 4.4 Earth days — short enough that 83 of its years would fit into one Earth year.
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