The star
The star
YZ Ceti
- Type
- M4.5 V
- Surface
- ≈ 3,151 K
- Size
- 0.16 × the Sun
- Mass
- 0.14 × the Sun
- Brightness
- 0.00219 × the Sun
- Habitable zone
- 0.0445–0.0782 AU
The planets
YZ Ceti
YZ Cet b
- Year
- 2.02 days
- Distance from star
- 0.0163 AU
- Mass
- at least 0.7 Earths
- Size
- 0.91 × Earth
- Temperature
- ≈ 471 K (+198 °C)
- Found
- 2017, radial velocity (La Silla Observatory)
YZ Ceti
YZ Cet c
- Year
- 3.06 days
- Distance from star
- 0.0216 AU
- Mass
- at least 1.1 Earths
- Size
- 1.1 × Earth
- Temperature
- ≈ 410 K (+137 °C)
- Found
- 2017, radial velocity (La Silla Observatory)
YZ Ceti
YZ Cet d
- Year
- 4.66 days
- Distance from star
- 0.0285 AU
- Mass
- at least 1.1 Earths
- Size
- 1 × Earth
- Temperature
- ≈ 357 K (+84 °C)
- Found
- 2017, radial velocity (La Silla Observatory)
Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.
How we know
The wobble
The planet tugs its star back and forth. Spectrographs measure the tiny shift in the star's light, which gives the planet's year and a minimum mass.
Sources
- Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 31 Oct 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
- Position: HYG Database v4.1 (CC BY-SA 4.0).
- Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.