TOI-199 b
TOI-199 b is a cold gas giant orbiting the G9 V star TOI-199 in the constellation Dorado. It lies about 334 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-199 b?
TOI-199 b has a radius of 9.08 times that of Earth, or 0.81 times the radius of Jupiter. Its mass is 54.0 times that of Earth.
Is TOI-199 b in the Habitable Zone?
TOI-199 b orbits inside the inner edge of the habitable zone of TOI-199. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-199: 0.524–1.254 AU (conservative: 0.664–1.189 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-199 b — one full orbit around TOI-199 — lasts 104.9 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.425 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.09).
How Was TOI-199 b Discovered?
TOI-199 b was discovered in 2023 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-199 b?
TOI-199 b is 333.6 light-years (102.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1693. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,871,360 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-199 b scores 0.35, ranking #736 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-199
TOI-199
- Spectral type
- G9 V
- Surface temperature
- 5,255 K (Sun: 5,772 K)
- Mass
- 0.94 M☉
- Radius
- 0.82 R☉
- Luminosity
- 0.4590 L☉
- Age
- 0.8 billion years (Sun: 4.6)
The TOI-199 Planetary System
TOI-199 b is one of 2 known planets in the TOI-199 system. Its siblings:
- TOI-199 c (Cold Gas Giant)
TOI-199 b — Complete Data
| Radius | 9.079 Earth radii (0.810 Jupiter radii) |
|---|---|
| Mass | 54.03 Earth masses (0.170 Jupiter masses) |
| Orbital period | 104.85 days |
| Orbital distance | 0.425 AU |
| Eccentricity | 0.090 |
| Earth Similarity Index | 0.35 |
| Distance from Earth | 333.6 light-years (102.3 parsecs) |
| Constellation | Dorado |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-10-09. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-199 b
Is TOI-199 b habitable?
No — TOI-199 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-199 b?
TOI-199 b is about 334 light-years from Earth in the constellation Dorado. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,871,360 years to get there.
How big is TOI-199 b compared to Earth?
TOI-199 b has 9.08 times the radius of Earth and about 54.0 times its mass.
How long is a year on TOI-199 b?
One orbit around TOI-199 takes 104.9 Earth days.
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