Astrometry

astrometricastrometricalastrometristastrometric measurementsastrometric observationsastrometricsastronomical observationsastrometric positionsastrometric scienceAstrometric stations
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.wikipedia
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Astronomy

astronomicalastronomerastronomers
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is now often considered to be synonymous with astrophysics.

Binary star

spectroscopic binaryeclipsing binarybinary
He made the first measurement of stellar parallax: 0.3 arcsec for the binary star 61 Cygni.
They may also be detected by indirect techniques, such as spectroscopy (spectroscopic binaries) or astrometry (astrometric binaries).

Proper motion

proper motionsproper-motionhigh proper motion star
During its 4-year run, the positions, parallaxes, and proper motions of 118,218 stars were determined with an unprecedented degree of accuracy.
Proper motion is the astronomical measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars.

Hipparcos

HIPTYCHipparcos satellite
In 1989, the European Space Agency's Hipparcos satellite took astrometry into orbit, where it could be less affected by mechanical forces of the Earth and optical distortions from its atmosphere.
It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky.

Filar micrometer

micrometerfilar micrometer,
Being very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century, mostly by use of the filar micrometer.
A filar micrometer is a specialized eyepiece used in astronomical telescopes for astrometry measurements, in microscopes for specimen measurements, and in alignment and surveying telescopes for measuring angles and distances on nearby objects.

Stellar parallax

parallax shiftparallaxparallax method
James Bradley first tried to measure stellar parallaxes in 1729.
Even with 21st-century techniques in astrometry, the limits of accurate measurement make distances farther away than about 100 parsecs (or roughly 300 light years) too approximate to be useful when obtained by this technique.

Cosmic distance ladder

standard candlestandard candlesdistance
Astrometry is an important step in the cosmic distance ladder because it establishes parallax distance estimates for stars in the Milky Way.
The precise measurement of stellar positions is part of the discipline of astrometry.

Gaia (spacecraft)

GaiaGaia spacecraftGaia'' spacecraft
The European Space Agency's Gaia Mission, launched in 2013, applies astrometric techniques in its stellar census.
The spacecraft is designed for astrometry: measuring the positions, distances and motions of stars with unprecedented precision.

Minute and second of arc

masarcsecondarc second
He made the first measurement of stellar parallax: 0.3 arcsec for the binary star 61 Cygni. Like the earlier catalogs of Hipparchus and Ptolemy, Ulugh Beg's catalogue is estimated to have been precise to within approximately 20 minutes of arc.
The ESA astrometric space probe Gaia, launched in 2013, can approximate star positions to 7 microarcseconds (µas).

Astrograph

astrograph telescopeastrographic cameraastrographic telescopes
Astrographs using astronomical photographic plates sped the process in the early 20th century.
Astrographs used in astrometry record images that are then used to "map" the positions of objects over a large area of the sky.

Space Interferometry Mission

SIMSIM Lite Astrometric ObservatorySpace Interferometry Mission (SIM)
NASA's planned Space Interferometry Mission (SIM PlanetQuest) (now cancelled) was to utilize astrometric techniques to detect terrestrial planets orbiting 200 or so of the nearest solar-type stars.
The Deep Search was to be the most demanding in terms of astrometric accuracy, hence the name, Deep Search.

Observational astronomy

astronomical observationobservationsobservational
In observational astronomy, astrometric techniques help identify stellar objects by their unique motions.
For objects that are relatively close to the Sun and Earth, direct and very precise position measurements can be made against a more distant (and thereby nearly stationary) background.

Star catalogue

star catalogNLTTLTT
The history of astrometry is linked to the history of star catalogues, which gave astronomers reference points for objects in the sky so they could track their movements.
The Smithsonian Astrophysical Observatory catalogue was compiled in 1966 from various previous astrometric catalogues, and contains only the stars to about ninth magnitude for which accurate proper motions were known.

Photographic plate

photographic platesglass plateglass plates
Astrographs using astronomical photographic plates sped the process in the early 20th century.
Several important applications of astrophotography, including astronomical spectroscopy and astrometry, continued using plates until digital imaging improved to the point where it could outmatch photographic results.

Parallax

trigonometric parallaxsolar parallaxmotion parallax
Astrometry is an important step in the cosmic distance ladder because it establishes parallax distance estimates for stars in the Milky Way.
The open stellar cluster Hyades in Taurus extends over such a large part of the sky, 20 degrees, that the proper motions as derived from astrometry appear to converge with some precision to a perspective point north of Orion.

Near-Earth object

near-Earth asteroidNEOnear-Earth
Astronomers use astrometric techniques for the tracking of near-Earth objects.
The designation was similarly removed from asteroid catalogues when the observed object was identified with Gaia, ESA's space observatory for astrometry.

Celestial mechanics

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

List of exoplanets detected by radial velocity

The true masses can be determined when astrometry calculates the inclination of the orbit.

Karl Wilhelm Reinmuth

K. Reinmuthdiscovered 395 asteroidsKarl Reinmuth
Reinmuth obtained more than 12,500 precise astrometric measurements of minor planets positions on photographic plates, an enormous work task before the advent of any computer based assistance.

William Ernest Cooke

W(illiam) Ernest Cooke
William Ernest Cooke (25 July 1863 – 7 November 1947), generally referred to as W. Ernest Cooke or informally Ernest Cooke, was an Australian astronomer, credited with a number of important scientific breakthroughs and improved methodologies in astronomical observations and star cataloguing.

List of minor planets

minor planet catalogindexCatalog
Observatories, telescopes and surveys that report astrometric observations of small Solar System bodies to the MPC receive a numeric or alphanumeric code such as 675 for the Palomar Observatory, or I41 for the Palomar Transient Factory, a dedicated survey that was conducted at Palomar Observatory during 2009–2012.

Barycentric celestial reference system

The barycentric celestial reference system (BCRS) is a coordinate system used in astrometry to specify the location and motions of astronomical objects.

International Celestial Reference Frame

ICRFcelestial reference frameInternational Celestial Reference Frame (ICRF)
In astrometry, an International Celestial Reference Frame (ICRF) is a realization of the International Celestial Reference System (ICRS) using reference celestial sources observed at radio wavelengths.