Tau Ceti is the closest single star that genuinely resembles the Sun, and it has been a fixture of the search for other Earths since 1960. Its planets, however, are a lesson in how hard that search is: an earlier claim of five planets has been whittled down, and the signals still on the books are all flagged as disputed.
Fly there in 3DEvery planet signal at Tau Ceti carries the NASA Exoplanet Archive’s controversy flag. The star is quiet by G-dwarf standards, but the wobbles involved are under a metre per second - the level at which starspots and convection start to look exactly like planets.
A debris disk ten times more massive than the Solar System’s Kuiper belt surrounds the star, extending from about 1 to 55 AU.
Tau Ceti and Epsilon Eridani were the two targets of Frank Drake’s Project Ozma in 1960 - the first deliberate search for radio signals from another civilisation.
| Spectral type | G8.5 V |
| Surface temperature | 5,310 K |
| Mass | 0.783 solar masses |
| Radius | 0.83 solar radii |
| Luminosity | 0.495 times the Sun |
| Apparent magnitude | 3.5 |
| Distance from the Sun | 11.9 light-years (3.7 parsecs) |
| Position (J2000) | RA 26.0170°, Dec -15.9375° |
| Constellation | Cetus |
| Planet | Year | Orbit | Radius | Mass | Found |
|---|---|---|---|---|---|
| Tau Ceti g disputed | 20.0 days | 0.133 AU | 1.18 R⊕ estimated | 1.75 M⊕ minimum | Radial Velocity, 2017 |
| Tau Ceti h disputed | 49.4 days | 0.243 AU | 1.19 R⊕ estimated | 1.83 M⊕ minimum | Radial Velocity, 2017 |
| Tau Ceti f disputed | 636.1 days | 1.334 AU | 1.81 R⊕ estimated | 3.93 M⊕ minimum | Radial Velocity, 2017 |
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.