Some Terms You Should Know: Astronomical Distances
These are some terms you will come across in your lab class dealing with
parallax and the measurement of astronomical distances.
-
Parallax
-
The apparent change in position of an object against a distant background
due to a change in the observer's position.
-
Parallax Angle
-
One half the angle a star appears to move due to parallax.
-
Parsec
-
A distance equal to 3.26 light years. An object one parsec away will have
a parallax angle of 1 second of arc when viewed from a baseline
of 1 AU.
-
Plate Scale
-
A conversion factor, for a specific photograph, of linear distance to angular
distance. (E.g., from cm to degrees.)
-
Apogee
-
The point in its orbit when an object orbiting the Earth is farthest from
the Earth.
-
Perigee
-
The point in its orbit when an object orbiting the Earth is closest to
Earth.
Back to the definitions page
This page was last updated on 30 March 1998
and is © 1998 by Jim McDonald.