TOI-561 c
TOI-561 c is a puffy low-density planet orbiting TOI-561 in the constellation Sextans. It lies about 280 light-years from Earth and was discovered in 2020 using the transit method.
How Big Is TOI-561 c?
TOI-561 c has a radius of 2.87 times that of Earth. Its mass is 5.9 times that of Earth, giving it a density of 1.30 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-561 c in the Habitable Zone?
The position of TOI-561 c relative to the habitable zone of TOI-561 cannot be precisely determined from the available orbital data.
Temperature on TOI-561 c
The equilibrium temperature of TOI-561 c is about 802 K (529 °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. It receives 67.50 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-561 c — one full orbit around TOI-561 — lasts 10.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.089 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.023).
How Was TOI-561 c Discovered?
TOI-561 c was discovered in 2020 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-561 c?
TOI-561 c is 279.8 light-years (85.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1747. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,924,480 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-561 c scores 0.23, ranking #3,490 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-561
TOI-561
- Mass
- 0.81 M☉
- Radius
- 0.84 R☉
The TOI-561 Planetary System
TOI-561 c is one of 4 known planets in the TOI-561 system. Its siblings:
TOI-561 c — Complete Data
| Radius | 2.865 Earth radii (0.256 Jupiter radii) |
|---|---|
| Mass | 5.93 Earth masses (0.019 Jupiter masses) |
| Density | 1.30 g/cm³ (Earth: 5.51) |
| Orbital period | 10.78 days |
| Orbital distance | 0.089 AU |
| Eccentricity | 0.023 |
| Equilibrium temperature | 802 K (529 °C) |
| Stellar irradiation | 67.50× Earth |
| Earth Similarity Index | 0.23 |
| Distance from Earth | 279.8 light-years (85.8 parsecs) |
| Constellation | Sextans |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2025-02-24. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-561 c
Is TOI-561 c habitable?
TOI-561 c is not known to orbit within the habitable zone of TOI-561, and as a puffy low-density planet it is an unlikely candidate for life as we know it.
How far away is TOI-561 c?
TOI-561 c is about 280 light-years from Earth in the constellation Sextans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,924,480 years to get there.
How big is TOI-561 c compared to Earth?
TOI-561 c has 2.87 times the radius of Earth and about 5.9 times its mass.
How long is a year on TOI-561 c?
One orbit around TOI-561 takes 10.8 Earth days — short enough that 34 of its years would fit into one Earth year.
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