What is Astrometry?
Astrometry is the science of determining the positions and motion of celestial objects. It is a specialized subfield of astronomy, which developed because accurate star positions were required for navigation. Astrometric measurements not only determine the position of objects on the celestial sphere (sky), but also can be used to measure the distances to stars. By measuring the change in a star’s position as the Earth revolves around the Sun, you can determine the distance to that star. This change in position is know as a star’s parallax. The concept of parallax was discovered by the ancient Greeks, who learned that the stars are very far away because they were not able to measure the parallax of any stars. It wasn’t until 1838 that German Mathematician and Astronomer Friedrich Bessel was able to measure the distance to the star 61 Cygnus. Distances to astronomical objects are very difficult to determine. The astronomical distance scale is determined by a series of methods that work a
