TOI-561 d
The parameters of this planet are disputed or ambiguous in the scientific literature.
TOI-561 d is a super-Earth 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 d?
TOI-561 d has a radius of 2.62 times that of Earth. Its mass is 13.3 times that of Earth, giving it a density of 4.10 g/cm³ — between that of rocky and gaseous planets.
Is TOI-561 d in the Habitable Zone?
The position of TOI-561 d relative to the habitable zone of TOI-561 cannot be precisely determined from the available orbital data.
Temperature on TOI-561 d
The equilibrium temperature of TOI-561 d is about 600 K (327 °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. It receives 21.20 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-561 d — one full orbit around TOI-561 — lasts 25.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.159 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.11).
How Was TOI-561 d Discovered?
TOI-561 d 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 d?
TOI-561 d 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 d scores 0.27, ranking #2,502 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 d is one of 4 known planets in the TOI-561 system. Its siblings:
TOI-561 d — Complete Data
| Radius | 2.615 Earth radii (0.233 Jupiter radii) |
|---|---|
| Mass | 13.33 Earth masses (0.042 Jupiter masses) |
| Density | 4.10 g/cm³ (Earth: 5.51) |
| Orbital period | 25.71 days |
| Orbital distance | 0.159 AU |
| Eccentricity | 0.111 |
| Equilibrium temperature | 600 K (327 °C) |
| Stellar irradiation | 21.20× Earth |
| Earth Similarity Index | 0.27 |
| 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 d
Is TOI-561 d habitable?
TOI-561 d is not known to orbit within the habitable zone of TOI-561, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is TOI-561 d?
TOI-561 d 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 d compared to Earth?
TOI-561 d has 2.62 times the radius of Earth and about 13.3 times its mass.
How long is a year on TOI-561 d?
One orbit around TOI-561 takes 25.7 Earth days — short enough that 14 of its years would fit into one Earth year.
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