دیدگشت ِ ستاره didgašt-e setâré
*Fr.: parallaxe stellaire*
The apparent → *difference* in the → *position*
of a → *celestial object* as seen by an → *observer*
from two widely separated → *location*s.
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 unit*s)
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).
See also: → *annual parallax*,
→ *diurnal parallax*,
→ *dynamical parallax*,
→ *geocentric parallax*,
→ *heliocentric parallax*,
→ *horizontal parallax*,
→ *lunar parallax*,
→ *mean parallax*,
→ *parallactic ellipse*,
→ *parsec*,
→ *photometric parallax*,
→ *secular parallax*,
→ *solar parallax*,
→ *spectroscopic parallax*,
→ *statistical parallax*,
→ *trigonometric parallax*. → *stellar*; → *parallax*. |