Lutz Kelker bias
Encyclopedia
The Lutz-Kelker bias is a systematic bias that applies to measurements of astronomical distance. In particular, it causes measured parallax
es to stars to be larger than their actual values. This causes inferred luminosities and distances to be too small, which poses a problem to astronomers trying to measure distance. The existence of this bias and the necessity of correcting for it has recently become relevant in astronomy with the precision parallax measurements made by the Hipparcos
satellite.
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
es to stars to be larger than their actual values. This causes inferred luminosities and distances to be too small, which poses a problem to astronomers trying to measure distance. The existence of this bias and the necessity of correcting for it has recently become relevant in astronomy with the precision parallax measurements made by the Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
satellite.