Achird (Eta Cassiopeiae)   HOME INDEX BACK NEXT

Double star in Cassiopeia

Star-hop chart

Achird is the "sixth star" in the W shape of Cassiopeia, and it is easily visible as a single star with the naked eye. Through a telescope at moderate or high power, it appears as a beautiful double star.

This double star is interesting for several reasons. First, it is relatively nearby at a distance of just 19.4 light years; only a few dozen stars are closer. Second, the brighter star of the pair is approximately the same size and brightness as our Sun. Third, the two stars display contrasting colors, which some have described as yellow and purple. The two stars are about 71 astronomical units apart.

Magnitudes 3.4, 7.5
Separation 13.4"
Distance (light yrs) 19.4
Right Ascension 0:49.1
Declination +57 49
Field of View 26' x 17'

Image details:  Five exposures each of 1/80, 1/20, 1/5, 1, and 4 seconds at ISO 12800, taken with a Canon T6i camera through a Meade 14” LX850 telescope at f/8. 

January 2018