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Astrometry

 
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Astrometry is the branch of astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 that relates to precise measurements and explanations of the positions and movements of star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
s and other celestial bodies. Although once thought of as an esoteric field with little useful application for the future, the information obtained by astrometric measurements is now very important in contemporary research into the kinematics
Kinematics

Kinematics is a branch of classical mechanics which describes the motion of objects without consideration of the causes leading to the motion....
 and physical origin of our Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 and our Galaxy
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
, the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
.

Applications
Apart from the fundamental function of providing astronomer
Astronomer

An astronomer is a scientist who studies Celestial body such as planets, stars, and Galaxy.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws....
s with a reference frame
Frame of reference

A frame of reference in physics, may refer to a coordinate system or Cartesian coordinate system within which to measure the position, orientation , and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an Observer ....
 to report their observations in, astrometry is also fundamental for fields like celestial mechanics
Celestial mechanics

Celestial mechanics is the branch of astronomy that deals with the motion s of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data....
, stellar dynamics
Stellar dynamics

Stellar dynamics is the branch of astrophysics which describes in a statistical way the collective motions of stars subject to their mutual gravity....
 and galactic astronomy
Galactic astronomy

Galactic astronomy is the study of our own Milky Way galaxy and all its contents. This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies....
.






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Interferometric Astrometry
Astrometry is the branch of astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 that relates to precise measurements and explanations of the positions and movements of star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
s and other celestial bodies. Although once thought of as an esoteric field with little useful application for the future, the information obtained by astrometric measurements is now very important in contemporary research into the kinematics
Kinematics

Kinematics is a branch of classical mechanics which describes the motion of objects without consideration of the causes leading to the motion....
 and physical origin of our Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 and our Galaxy
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
, the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
.

Applications


Apart from the fundamental function of providing astronomer
Astronomer

An astronomer is a scientist who studies Celestial body such as planets, stars, and Galaxy.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws....
s with a reference frame
Frame of reference

A frame of reference in physics, may refer to a coordinate system or Cartesian coordinate system within which to measure the position, orientation , and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an Observer ....
 to report their observations in, astrometry is also fundamental for fields like celestial mechanics
Celestial mechanics

Celestial mechanics is the branch of astronomy that deals with the motion s of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data....
, stellar dynamics
Stellar dynamics

Stellar dynamics is the branch of astrophysics which describes in a statistical way the collective motions of stars subject to their mutual gravity....
 and galactic astronomy
Galactic astronomy

Galactic astronomy is the study of our own Milky Way galaxy and all its contents. This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies....
. In observational astronomy
Observational astronomy

Observational astronomy is a division of the astronomy science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measurable implications of physical model s....
, astrometric techniques help identify stellar objects by their unique motions. It is instrumental for keeping time
Time

Time is a component of the measurement used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects....
, in that UTC
Coordinated Universal Time

Coordinated Universal Time is a time standard based on International Atomic Time with leap seconds added at irregular intervals to compensate for the Earth's slowing rotation....
 is basically the atomic time
International Atomic Time

International Atomic Time is a high-precision atomic coordinate time time standard based on the notional passage of proper time on Earth's geoid....
 synchronized to Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
's rotation by means of exact observations. Astrometry is also involved in creating the cosmic distance ladder
Cosmic distance ladder

File:Extragalactic distance ladder.JPGThe cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects....
 because it is used to establish parallax
Parallax

Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines....
 distance estimates for stars in the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
.

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
Space Interferometry Mission

The Space Interferometry Mission, also known as SIM PlanetQuest, is a planned Space observatory being developed by the U.S. National Aeronautics and Space Administration , in conjunction with contractor Northrop Grumman....
 (SIM PlanetQuest) will utilize astrometric techniques to detect terrestrial planets orbiting 200 or so of the nearest solar-type stars
Solar analog

Solar Twins redirects here. For the musical group, please see Solar Twins Solar-Type, Solar Analog, and Solar Twin stars are those stars that are particularly similar to the Sun, with solar twin being more similar than solar analog, and solar-type being less similar than solar analog....
.

Astrometric measurements are used by astrophysicists to constrain certain models in celestial mechanics
Celestial mechanics

Celestial mechanics is the branch of astronomy that deals with the motion s of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data....
. By measuring the velocities of pulsar
Pulsar

Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds....
s, it is possible to put a limit on the asymmetry
Asymmetry

Asymmetry is the absence of, or a violation of, a symmetry....
 of supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
 explosions. Also, astrometric results are used to determine the distribution of dark matter
Dark matter

In astronomy and physical cosmology, dark matter is Hypothesis matter that is undetectable by its emitted electromagnetic radiation, but whose presence can be inferred from gravity effects on visible matter....
 in the galaxy.

Astrometry is responsible for the detection of many record-breaking solar system objects. To find such objects astrometrically, astronomers use telescopes to survey the sky and large-area cameras to take pictures at various determined intervals. By studying these images, we can notice solar system objects by their movements relative to the background stars, which remain fixed. Once a movement per unit time is observed, astronomers compensate for the amount of parallax caused by the earth’s motion during this time and the heliocentric distance to this object is calculated. Then, using this distance and other photographs, more information about the object, such as parallax, proper motion, and the semimajor axis of its orbit, can be obtained.

Quaoar and 90377 Sedna
90377 Sedna

90377 Sedna is a trans-Neptunian object and a likely dwarf planet, discovered by Michael E. Brown , Chad Trujillo and David L. Rabinowitz on November 14, 2003....
 are two solar system objects discovered in this way by Michael E. Brown
Michael E. Brown

Michael E. Brown has been a professor of planetary astronomy at the California Institute of Technology since 2003. He was previously an associate professor at Caltech from 2002-2003 and an assistant professor at Caltech from 1997?2002....
 and others at Caltech using the Palomar Observatory
Palomar Observatory

Palomar Observatory is a privately owned observatory located in San Diego County, California, 90 miles southeast of Mount Wilson Observatory, on Palomar Mountain in the Palomar Mountain Range....
’s Samuel Oschin telescope
Samuel Oschin telescope

The Samuel Oschin telescope is a 48-inch aperture Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch mirror....
 of and the Palomar-Quest large-area CCD camera. The ability of astronomers to track the positions and movements of such celestial bodies is crucial to the understanding of our Solar System and its interrelated past, present, and future with others in our Universe.

Statistics


A fundamental aspect of astrometry is error correction. Various factors introduce errors into the measurement of stellar positions, including atmospheric conditions, imperfections in the instruments and errors by the observer or the measuring instruments. Many of these errors can be reduced by various techniques, such as through instrument improvements and compensations to the data. The results are then analyzed using statistical methods
Statistics

Statistics is a Mathematics pertaining to the collection, analysis, interpretation or explanation, and presentation of data. It also provides tools for prediction and forecasting based on data....
 to compute data estimates and error ranges.

Computer programs

  • Astrometrica
  • MPO (computer program)


In fiction


  • In the fiction
    Fiction

    Fiction is an imaginative form of narrative, one of the four basic rhetorical modes. Although the word fiction is derived from the Latin fingo, fingere, finxi, fictum, "to form, create", works of fiction need not be entirely imaginary and may include real people, places, and events....
    al Star Trek: Voyager
    Star Trek: Voyager

    Star Trek: Voyager is a science fiction television series set in the Star Trek universe. The show was created by Rick Berman, Michael Piller, and Jeri Taylor and is the fourth incarnation of Star Trek, which began with the 1960s series Star Trek: The Original Series, created by Gene Roddenberry....
    , the Astrometrics lab is the set for various scene
    Scene (fiction)

    In fiction, a scene is a unit of drama. A sequel is what follows, an aftermath. Together, scene and sequel provide the building blocks of plot for short story, novels, and other forms of fiction....
    s.
  • In the reimagined TV Show Battlestar Galactica
    Battlestar Galactica

    Battlestar Galactica is a Media franchise of science fiction films and television program, the Battlestar Galactica was produced in 1978. A series of book adaptations, original novels, comic books and video games have also been based on the concept....
     an Astrometrics lab is stated in dialogue multiple times.


See also


  • Astrometric binary
  • Ephemeris
    Ephemeris

    An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds are used for astronomy and astrology....
  • Equatorium
  • Gaia Probe
    Gaia probe

    Gaia is a European Space Agency astrometry space mission, and a successor to the ESA Hipparcos mission. It was included within the context of the ESA Horizon 2000 Plus long-term scientific programme in 2000....
     (ESA -- Planned for 2011-17)
  • Hipparcos Space Astrometry Mission
    Hipparcos

    Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to astrometry, the accurate measurement of star positions, parallaxes, and proper motions....
     (ESA -- 1989-93)
  • Spherical astronomy
    Spherical astronomy

    Spherical astronomy or positional astronomy is the branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth....
  • Star cartography
    Star cartography

    Star cartography, celestial cartography, or uranography is the fringe of astronomy and branch of cartography concerned with mapping the stars, galaxies, and a multitude of other celestial bodies....


Further reading


External links

  • A site for popularization of Astrometry and Celestial Mechanics, by the Scientia Astrophysical Organization.
  • Astrometry Department of the U.S. Naval Observatory


  • Mike Brown's Caltech Home Page
  • Scientific Paper describing Sedna's discovery