TOI-561 b
TOI-561 b is a lava world 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 b?
TOI-561 b has a radius of 1.40 times that of Earth. Its mass is 2.0 times that of Earth, giving it a density of 4.10 g/cm³ — between that of rocky and gaseous planets.
Is TOI-561 b in the Habitable Zone?
The position of TOI-561 b relative to the habitable zone of TOI-561 cannot be precisely determined from the available orbital data.
Temperature on TOI-561 b
The equilibrium temperature of TOI-561 b is about 2,319 K (2,046 °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 4,709 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-561 b — one full orbit around TOI-561 — lasts just 10.7 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.011 AU — closer to its star than Mercury is to the Sun.
How Was TOI-561 b Discovered?
TOI-561 b 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 b?
TOI-561 b 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 b scores 0.28, ranking #2,170 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 b is one of 4 known planets in the TOI-561 system. Its siblings:
TOI-561 b — Complete Data
| Radius | 1.397 Earth radii (0.125 Jupiter radii) |
|---|---|
| Mass | 2.02 Earth masses (0.006 Jupiter masses) |
| Density | 4.10 g/cm³ (Earth: 5.51) |
| Orbital period | 0.45 days |
| Orbital distance | 0.011 AU |
| Equilibrium temperature | 2,319 K (2,046 °C) |
| Stellar irradiation | 4,709.00× Earth |
| Earth Similarity Index | 0.28 |
| 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 b
Is TOI-561 b habitable?
TOI-561 b is not known to orbit within the habitable zone of TOI-561, and as a lava world it is an unlikely candidate for life as we know it.
How far away is TOI-561 b?
TOI-561 b 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 b compared to Earth?
TOI-561 b has 1.40 times the radius of Earth and about 2.0 times its mass.
How long is a year on TOI-561 b?
One orbit around TOI-561 takes 0.4 Earth days — short enough that 818 of its years would fit into one Earth year.
Explore TOI-561 b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
