Astrometry

Astrometry is a branch of astronomy that deals with the positions of stars and other celestial bodies, their distances and movements.

Related Topics:
Astronomy - Star - Celestial bodies

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It is one of the oldest subfields of the science, the successor to the more qualitative study of positional astronomy. Astrometry dates back at least to Hipparchus, who compiled the first catalogue of stars visible to him and in doing so invented the brightness scale basically still in use today. Modern astrometry was founded by Friedrich Bessel with his Fundamenta astronomiae, which gave the mean position of 3222 stars observed between 1750 and 1762 by James Bradley.

Related Topics:
Science - Positional astronomy - Hipparchus - Catalogue of stars - Brightness scale - Friedrich Bessel - James Bradley

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Apart from the fundamental function of providing Astronomers with a reference frame to report their observations in, astrometry is also fundamental for fields like celestial mechanics, stellar dynamics and galactic astronomy. In observational astronomy, astrometric techniques help identify stellar objects by their unique motions. It is instrumental for keeping time, in that UTC is basically the atomic time synchronized to Earth's rotation by means of exact observations. Astrometry is also involved in creating the cosmic distance ladder because it is used to establish parallax distance estimates for stars in the Milky Way.

Related Topics:
Astronomer - Reference frame - Celestial mechanics - Stellar dynamics - Galactic astronomy - Observational astronomy - Time - UTC - Atomic time - Earth - Cosmic distance ladder - Parallax - Milky Way

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