Parallax
type: Concept
narrower: Stellar parallax

Stellar distance
type: Concept
related: Stellar parallax

Solar parallax
type: Concept
broader: Stellar parallax

Stellar parallax
type: Concept
broader: Parallax
related: Stellar distance
narrower: Solar parallax
modified: 2020-11-19T16:19:32.487Z
modified: 2020-11-19T16:19:14.992Z
contributor: AAS Frey.Katie
definition: The apparent difference in the position of a celestial object as seen by an observer from two widely separated locations. The parallax of an object can be used to derive its distance. The relationship between the parallax angle p (measured in seconds of arc) and the distance d (measured in astronomical units) is given by d = 206,264 / p. For a parallax angle p = 1'', the distance to the star would correspond to 206,264 AU. By convention, the distance unit parsec is defined to be equivalent to 206,264 AU. Therefore, the parallax relation takes the much simpler form: d (in pc) = 1/p (in seconds of arc). The first star whose parallax was measured was 61 Cygni (Bessel, 1838).