Chapter 16
Astrometry
Abstract Astrometry deals with the position and movement of astronomical objects
in the sky. It is one of the most ancient applications of astronomy, and in its modern
form, it is used to determine to the position of stars within the galaxy and the orbits
of comets and asteroids, and to detect the existence of exoplanets. We show how to
perform astrometry using SAO DS9 to determine the proper motion of an asteroid,
and from that its distance from the Sun.
16.1 Introduction
Astrometry deals with the position and the movement of astrophysical bodies like the
planets, asteroids, comets, and stars. The production of an astronomical catalogue,
with the positions of those objects, requires astrometric observations and calculations.
Astrometry is the oldest scientific application of astronomy, as it was the astronomical measurements of Tycho Brahe that allowed Kepler to develop his three laws
of planetary of motion and Newton to discover his law of universal gravitation. It
also gave the first hint that Newton was incorrect, leading to Einstein developing
general and special relativity, which we first confirmed through observation of stars
during an eclipse.
In modern astronomy, astrometry helped in the discovery of the supermassive
black hole in the galactic centre as well as, indirectly, in the detection of exoplanets.
Astrometry is one of the techniques we can use to determine the distances to
the stars. The method of stellar parallax requires very high precision astrometry to
measure the angular displacement of a nearby star when referenced to more distant
stars, caused by the rotation of the Earth around the Sun. A 1 arcsec displacement is
equal to a distance of 1 pc. However, parallax-related changes for a source beyond
100 pc are difficult to detect. Although there has been some progress with very long
baseline radio interferometry that has positional resolutions of sub-milliarcseconds,
this pushes direct distance measurements out to kiloparsecs for radio sources, some of
which, for example masers, are associated with other features such as star formation.
© Springer Nature Switzerland AG 2020
M. Gallaway, An Introduction to Observational Astrophysics,
Undergraduate Lecture Notes in Physics,
https://doi.org/10.1007/978-3-030-43551-6_16
217
Astrometry
Abstract Astrometry deals with the position and movement of astronomical objects
in the sky. It is one of the most ancient applications of astronomy, and in its modern
form, it is used to determine to the position of stars within the galaxy and the orbits
of comets and asteroids, and to detect the existence of exoplanets. We show how to
perform astrometry using SAO DS9 to determine the proper motion of an asteroid,
and from that its distance from the Sun.
16.1 Introduction
Astrometry deals with the position and the movement of astrophysical bodies like the
planets, asteroids, comets, and stars. The production of an astronomical catalogue,
with the positions of those objects, requires astrometric observations and calculations.
Astrometry is the oldest scientific application of astronomy, as it was the astronomical measurements of Tycho Brahe that allowed Kepler to develop his three laws
of planetary of motion and Newton to discover his law of universal gravitation. It
also gave the first hint that Newton was incorrect, leading to Einstein developing
general and special relativity, which we first confirmed through observation of stars
during an eclipse.
In modern astronomy, astrometry helped in the discovery of the supermassive
black hole in the galactic centre as well as, indirectly, in the detection of exoplanets.
Astrometry is one of the techniques we can use to determine the distances to
the stars. The method of stellar parallax requires very high precision astrometry to
measure the angular displacement of a nearby star when referenced to more distant
stars, caused by the rotation of the Earth around the Sun. A 1 arcsec displacement is
equal to a distance of 1 pc. However, parallax-related changes for a source beyond
100 pc are difficult to detect. Although there has been some progress with very long
baseline radio interferometry that has positional resolutions of sub-milliarcseconds,
this pushes direct distance measurements out to kiloparsecs for radio sources, some of
which, for example masers, are associated with other features such as star formation.
© Springer Nature Switzerland AG 2020
M. Gallaway, An Introduction to Observational Astrophysics,
Undergraduate Lecture Notes in Physics,
https://doi.org/10.1007/978-3-030-43551-6_16
217