Alpha Andromedae

From Citizendium
Jump to navigation Jump to search
This article is developing and not approved.
Main Article
Related Articles  [?]
Bibliography  [?]
External Links  [?]
Citable Version  [?]
This editable Main Article is under development and subject to a disclaimer.

α Andromedae, or Alpheratz, is a bright star in the constellation of Andromeda located on the northeast corner of the asterism known as the Great Square of Pegasus.

Naming and mythology

Alpheratz, sometimes called Sirrah, was originally named Al Surrat al Faras, the horse's navel, by Arab astronomers before Ptolemy named the star Al Rās al Marʼah al Musalsalah which represented the head of Andromeda.[1]

Observational attributes

Alpheratz has an apparent magnitude of 2.06[2] and can be located at coordinates R.A. 0h 8m 23.3s and Dec. +29° 5ˈ 26ˈˈ. The parallax for Alpheratz is 0.032ˈˈ translating into a distance from Earth of roughly 101 light years.

Physical characteristics

α Andromedae is a spectroscopic binary star with a main component of magnitude 2.06 and a companion star of magnitude 11.4. The stars orbit each other with a period of 96.7 days.[3] The spectral class of the main star is B8IV with lines of manganese and mercury as well as gallium(II) apparent in the spectrum. The spectral class indicates a surface temperature for α Andromedae at around 13.000 kelvin and a luminosity of some 200 solar luminosities. The radius of the star is estimated at around 5 times that of the sun.[2]

The main component of α Andromedae is classified as a variable star of the α2 Canum venaticorum variety. Its brightness varies between magnitude 2.02 and 2.06 with a period of 0.966222 days.[4]


  1. Star Names: Their Lore and Meaning, Richard H. Allen, Dover Publications 1963 (revised edition)
  2. 2.0 2.1 Bright Star Catalog 5th revised edition, 1991
  3. The Washington Visual Double Star Catalog, 1996
  4. Combined General Catalogue of Variable Stars, 1998