Parallax distances require extremely accurate measurements of the centroids of
stars. However, from Earth, stars look 'fuzzy' due to atmospheric distortion. Absolute
centroids, and their relative motion against the centroids of other stars, is
better measured from space. This was the reason for the Hipparcos Space
Mission, which flew in the mid-90s.
The Hipparcos Mission:
was the first space mission dedicated to measuring the positions of the stars.
measured the position of stars to an accuracy of 0.001'' (equivalent to
the angular size of a golf ball viewed from the other side of the Atlantic Ocean).
has allowed astronomers to measure, for the first time, distances of tens of
thousands of stars in our Galaxy, and the motions of these stars through space.
What did the Hipparcos Astronomers use for STANDARDS?
