The star
The star
WASP-21
- Type
- G3 V
- Surface
- ≈ 5,800 K
- Size
- 1.06 × the Sun
- Mass
- 1.01 × the Sun
- Brightness
- 2.01 × the Sun
- Habitable zone
- 1.06–2.5 AU
The planets
WASP-21
WASP-21 b
- Year
- 4.32 days
- Distance from star
- 0.052 AU
- Mass
- 95 Earths
- Size
- 12 × Earth
- Temperature
- ≈ 1333 K (+1060 °C)
- Found
- 2010, transit (SuperWASP)
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 shadow
The planet passes in front of its star and dims it by a fraction of a percent, every orbit. The dip gives the planet's size and year.
Sources
- Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 1 Nov 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.