Astrometry
Astrometry is a branch of
astronomy that deals with the positions of
stars and other celestial bodies, their distances and movements.
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.
Encyclopedia
Astrometry is a branch of
astronomy that deals with the positions of
stars and other celestial bodies, their distances and movements.
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.
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.
Advances in astrometry
...
s were effective at measuring time.
- Astrolabes were invented for measuring celestial angles.
- Astrometric applications led to the development of spherical geometry
- Careful measurement of planetary motions by Tycho Brahe, followed by analysis by Johannes Kepler proved the Copernican principle, that Earth revolves about the Sun
|-
...
.
- The sextant dramatically improved measurement of celestial angles.
- James Bradley measured stellar aberration with a precise transit telescope.
- The development of charge coupled devices , and their adoption by astronomers in the 1980s, improved the precision of professional astrometric work.
- The development of inexpensive CCDs, software, and telescopes allowed for large-scale amateur astrometric observation of minor planets.
- From 1989 to 1993, the European Space Agency's Hipparcos satellite performed astrometric measurements resulting in a catalogue of positions accurate to 20-30 milliarcsec for over a million stars.
Astronomers use astrometric techniques for the tracking of
near-Earth objects. It has been also been used to detect
extrasolar planets by measuring the displacement they cause in their parent star's apparent position on the sky, due to their mutual orbit around the center of mass of the system. NASA's planned
Space Interferometry Mission will utilize astrometric techniques to detect
terrestrial planets orbiting 200 or so of the nearest solar-type stars.
Astrometric measurements are used by
astrophysicists to constrain certain models in celestial mechanics. By measuring the velocities of
pulsars, it is possible to put a limit on the
asymmetry of
supernova explosions. Also, astrometric results are used to determine the distribution of
dark matter in the galaxy.
Astrometrics
Astrometrics is the
science of
stellar measurements and motion. Astrometrics was used, during the 1990s, to detect
extrasolar gas giants orbiting various
solar systems. This was done by observing the "stellar wobble" of a star and calculating what kinds of
gravitational forces would cause such motion; it was then determined that
planetary forces must be affecting the stars in question.
References
- Jean Kovalevsky and P. Kenneth Seidelman, Fundamentals of Astrometry, Cambridge University Press, 2004, ISBN 0-521-64216-7.
In fiction
In the
fictional
, the
Astrometrics lab is the
set for various scenes.
See also
