Astrophysics (Index)About

optical double

(apparent binary)
(double star where the two are not gravitationally bound)

The meaning of term optical double (or apparent binary) is a double star (two stars close together in the celestial sphere) that don't constitute a binary star (two stars co-orbiting) but because of chance alignment of the two stars with us. They are "optical" in that they look like a binary. The term physical double is sometimes used for an actual binary star.

(star type,double stars)
Further reading:

Referenced by pages:
Aitken Double Star Catalogue (ADS)
binary star
blended spectra
double star designation