TOI-199 c
TOI-199 c 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 timing variations method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is TOI-199 c in the Habitable Zone?
TOI-199 c orbits inside the conservative habitable zone of TOI-199 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
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 c — one full orbit around TOI-199 — lasts 273.7 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.807 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.10).
How Was TOI-199 c Discovered?
TOI-199 c was discovered in 2023 using the transit timing variations method, with observations from Multiple Observatories.
Transit timing variations reveal a planet through its gravitational tug on a sibling planet, which makes that sibling's transits arrive slightly early or late. The pattern of these deviations betrays the hidden planet's mass and orbit.
How Far Away Is TOI-199 c?
TOI-199 c 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 c scores 0.39, ranking #497 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 c is one of 2 known planets in the TOI-199 system. Its siblings:
- TOI-199 b (Cold Gas Giant)
TOI-199 c — Complete Data
| Mass | 88.99 Earth masses (0.280 Jupiter masses) |
|---|---|
| Orbital period | 273.69 days |
| Orbital distance | 0.807 AU |
| Eccentricity | 0.096 |
| Earth Similarity Index | 0.39 |
| Distance from Earth | 333.6 light-years (102.3 parsecs) |
| Constellation | Dorado |
| Discovery method | Transit Timing Variations |
| Discovery facility | Multiple Observatories |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-10-09. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-199 c
Is TOI-199 c habitable?
TOI-199 c orbits within the habitable zone of TOI-199, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is TOI-199 c?
TOI-199 c 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 long is a year on TOI-199 c?
One orbit around TOI-199 takes 273.7 Earth days.
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