Astrometry

Syllabus Requirements

2. Careful measurement of a celestial object’s position in the sky (astrometry) may be used to determine its distance

• define the terms parallax, parsec, light-year
• explain how trigonometric parallax can be used to determine the distance to stars
• discuss the limitations of trigonometric parallax measurements
• solve problems and analyse information to calculate the distance to a star given its trigonometric parallax using:
  d = 1/p
• gather and process information to determine the relative limits to trigonometric parallax distance determinations using recent ground-based and space-based telescopes

What is Astrometry?

Astrometry is perhaps the oldest of all branches of Astronomy. It is the branch concerned with the accurate measurement of the positions and proper motion of celestial objects such as stars. Hipparchus (c 130 BC) combined the arithmetical astronomy of the Babylonians with the geometrical approach of the Greeks to develop a model for solar and lunar motions. He also compiled a catalogue of the stars and established a method for comparing brightnesses.

Why though is astrometry still important today? To find out, follow the link.