EZ Aquarii A
Star
EZ Aquarii A - the brighter component of a triple system of tiny red dwarfs 11.1 light-years away in Aquarius, the nearest triple star after Alpha Centauri. This component is itself an unresolved pair of red dwarfs circling each other every 3.8 days; a third star orbits the pair every 2.3 years. All flare. No planets are confirmed.
Open in 3D viewSee EZ Aquarii A in the live, interactive 3D map
Key facts
Mutual orbit
823 Earth days
2.25 Earth years
Mass
4.21 × 10²⁹ kg
0.212 M☉
Radius
139,140 km
20% of the Sun's radius
Surface temperature
2,900 K (2,627 °C)
Luminosity
5.74 × 10²³ W
Spectral type
M5V (red dwarf)
Science
Physical
- Mass
- 4.21 × 10²⁹ kg · 0.212 M☉
- Radius
- 139,140 km · 20% of the Sun's radius
- Density
- 37,316 kg/m³ · 37× water
- Computed from mass and radius
- Spectral type
- M5V (red dwarf)
Motion through space
- Note
- Catalogued for the system as a whole: the motion of its stars' common centre of mass.
- Proper motion
- 3.26 arcseconds per year · its drift across our sky
- SIMBAD — 2012yCat.1322....0Z
- Speed across our line of sight
- 52.6 km/s
- Computed from proper motion and parallax
Orbit (around the system barycenter)
- Semi-major axis
- 0.414 AU
- From the triple-system orbit of Delfosse et al. 1999 (outer pair P = 822.6 d, e = 0.44; the inner pair is an unresolved 3.79-day spectroscopic binary)
- Eccentricity
- 0.439
- From the triple-system orbit of Delfosse et al. 1999 (outer pair P = 822.6 d, e = 0.44; the inner pair is an unresolved 3.79-day spectroscopic binary)
- Orbital period
- 2.25 years
- From the triple-system orbit of Delfosse et al. 1999 (outer pair P = 822.6 d, e = 0.44; the inner pair is an unresolved 3.79-day spectroscopic binary)
Composition
- By mass
- The combined light of an unresolved pair of red dwarfs (~0.21 solar masses together) orbiting every 3.8 days. Both are flare stars.
Temperature
- Surface
- 2,900 K (2,627 °C)
Radiation & temperature
- Luminosity
- 5.74 × 10²³ W · 0.0015 L☉
- Surface temperature
- 2,900 K (2,627 °C)
- Peak wavelength
- 999 nm · near-infrared (mostly invisible to the eye)
- Computed (Wien's law) from the surface temperature
Discovery & history
- Discovered
- 1935
- By
- Willem Luyten
- Method
- Telescope
- Name
- Named for its variable-star designation EZ Aquarii (a flare star in Aquarius); also Luyten 789-6 and GJ 866.
Catalogued by Willem Luyten (as Luyten 789-6) and later resolved into a triple by X. Delfosse and colleagues in 1999, whose precise orbits pinned each tiny mass to ~2% - a benchmark for the lowest-mass stars.
Images
Images from open archives · credit shown per image