Epsilon Scorpii

Stellar classification



  • X 12
  • Y 7
  • Z 62
→ Sol: 64

Object type

  • Variable Star
  • Star
  • Infra-Red source
  • High proper-motion Star
  • UV-emission source
  • X-ray source
simbad:* eps Sco


Epsilon Scorpii (ε Sco, ε Scorpii) is a star in the southern zodiac constellation of Scorpius. It has an apparent visual magnitude of +2.3, making it the fifth-brightest member of the constellation. Parallax measurements made during the Hipparcos mission provide an estimated distance to this star of around 63.7 light-years (19.5 parsecs).

Patrick Moore introduced the name Wei but this seems to be a misreading; Wěi (尾), meaning the Tail, was originally the name of a Chinese asterism or Xiù comprising the stars ε, μ12, ζ12, η, θ, ι, κ, υ, and λ Scorpii.

Epsilon Scorpii has a stellar classification of K1 III, which indicates it has exhausted the supply of hydrogen at its core and evolved into a giant star. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 5.99 ± 0.06 mas, which, at its estimated distance, equates to a physical radius of nearly 13 times the radius of the Sun. Presently it is generating energy through the nuclear fusion of helium at its core, which, considering the star's composition, places it along an evolutionary branch termed the red clump. The star's outer atmosphere has an effective temperature of 4,560 K, giving it the orange hue of a cool K-type star.

ε Scorpii is classified as a suspected variable star, although a study of Hipparcos photometry showed a variation of no more than 0.01–0.02 magnitudes. It is an X-ray source with a luminosity of (1.5–1.6) × 1027 erg s−1.

This article uses material from the Wikipedia article "Epsilon Scorpii", which is released under the Creative Commons Attribution-Share-Alike License 3.0.