TOI-521 is 199 light-years from the Sun. The NASA Exoplanet Archive lists 1 planet around this M3 star; the first was found in 2025 by transit (Transiting Exoplanet Survey Satellite (TESS)).
Fly there in 3DTOI-521 b goes round its star every 37.0 hours, 57 times as often as Mercury goes round the Sun.
| Spectral type | M3 |
| Surface temperature | 3,544 K |
| Mass | 0.42 solar masses |
| Radius | 0.421 solar radii |
| Luminosity | 0.0252 times the Sun |
| Apparent magnitude | 14.691 |
| Age | about 0.8 billion years |
| Distance from the Sun | 198.8 light-years (60.9 parsecs) |
| Position (J2000) | RA 123.3443°, Dec 12.2221° |
| Constellation | Cancer |
| Planet | Year | Orbit | Radius | Mass | Found |
|---|---|---|---|---|---|
| TOI-521 b | 37.0 hours | 0.0195 AU | 1.98 R⊕ | 5.3 M⊕ | Transit, 2025 |
Values are the NASA Exoplanet Archive’s composite parameters. A radius marked estimated comes from a mass–radius relation; a mass marked minimum is M sin i. Planet sizes and colours in the 3D view are renderings: none of these worlds has been photographed as more than a point of light.
For a star of 3,544 K, 0.025 times as bright as the Sun, the habitable zone, where starlight could keep water liquid on a rocky surface, runs from about 0.16 to 0.32 AU. None of its known planets orbits inside it. The zone says how much starlight arrives, not whether a planet has water or air. The edges follow Kopparapu et al. (2014), as the 3D view draws them.
The light you see left 199 years ago, around 1830.