Difference between revisions of "Astrometry" - New World Encyclopedia
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'''Astrometry''' is the branch of [[astronomy]] that relates to precise measurements and explanations of the positions and movements of [[stars]] 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]] and physical origin of our [[Solar System]] and our [[Galaxy]], the [[Milky Way]]. | '''Astrometry''' is the branch of [[astronomy]] that relates to precise measurements and explanations of the positions and movements of [[stars]] 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]] and physical origin of our [[Solar System]] and our [[Galaxy]], the [[Milky Way]]. | ||
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==History== | ==History== | ||
| − | 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. This can be dated back to [[Hipparchus]], who around 190 | + | 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. This can be dated back to [[Hipparchus]], who around 190 B.C.E. used the catalogue of his predecessors [[Timocharis]] and [[Aristillus]] to discover the earth’s [[precession]]. In doing so, he also invented the brightness scale still in use today. <ref>Hans G. Walter, ''Astrometry of fundamental catalogues : the evolution from optical to radio reference frames''. Berlin ; New York : Springer, 2000. ISBN 3540674365 ISBN 9783540674368</ref> |
| − | [[James Bradley]] first tried to measure stellar [[parallax]]es in | + | [[James Bradley]] first tried to measure stellar [[parallax]]es in 1729. The stellar movement proved too insignificant for his [[telescope]], but he instead discovered the [[aberration of light]] and the [[nutation]] of the Earth’s axis. His cataloging of 3222 stars was refined in 1807 by [[Friedrich Bessel]], the father of modern astrometry. He made the first measurement of stellar parallax: 0.3 [[arcsec]] for the [[binary star]] [[61 Cygni]]. |
| − | Being very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century. Automated plate-measuring machines and more sophisticated computer technology of the | + | Being very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century. Automated plate-measuring machines and more sophisticated [[computer technology]] of the 1960s allowed for larger compilations of star catalogues to be achieved more efficiently. In the 1980s, [[charge-coupled device]]s (CCDs) replaced photographic plates and reduced optical uncertainties to one milliarcsecond. This technology made astrometry less expensive, opening the field to an [[amateur]] audience. |
| − | In | + | 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]]. Operated from 1989 to 1993, Hipparcos measured large and small angles on the sky with much greater precision than any previous optical telescopes. During its 4-year run, the positions, parallaxes, and [[proper motions]] of 118,218 stars were determined with an incredible degree of accuracy. A new catalogue “Tycho” drew together a database of 1,058,332 to within 20-30 mas. Additional catalogues were compiled for the 23,882 double/multiple stars and 11,597 variable stars also analyzed during the Hipparcos mission.<ref>[http://www.rssd.esa.int/index.php?project=HIPPARCOS The Hipparcos Space Astrometry Mission] - ESA</ref> |
| − | Today, the catalogue most often used is USNO-B1.0, an all-sky catalogue that tracks proper motions, positions, magnitudes and other characteristics for over one billion stellar objects. During the past 50 years, 7,435 Schmidt plates were used to complete several sky surveys that make the data in USNO-B1.0 accurate to within 0.2 arcseconds. <ref>Kovalevsky, | + | Today, the catalogue most often used is USNO-B1.0, an all-sky catalogue that tracks proper motions, positions, magnitudes and other characteristics for over one billion stellar objects. During the past 50 years, 7,435 Schmidt plates were used to complete several sky surveys that make the data in USNO-B1.0 accurate to within 0.2 arcseconds. <ref>Jean Kovalevsky, ''Modern Astrometry''. Berlin ; New York : Springer, 2002. ISBN 354042380X ISBN 9783540423805</ref> |
==Applications== | ==Applications== | ||
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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]] ([[SIM PlanetQuest]]) will utilize astrometric techniques to detect [[terrestrial planets]] orbiting 200 or so of the nearest [[solar-type 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]] ([[SIM PlanetQuest]]) will utilize astrometric techniques to detect [[terrestrial planets]] orbiting 200 or so of the nearest [[solar-type stars]]. | ||
| − | Astrometric measurements are used by [[astrophysicist]]s to constrain certain models in [[celestial mechanics]]. By measuring the velocities of [[pulsar]]s, 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. | + | Astrometric measurements are used by [[astrophysicist]]s to constrain certain models in [[celestial mechanics]]. By measuring the velocities of [[pulsar]]s, 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]]. |
| − | 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. <ref>http://www.gps.caltech.edu/%7Embrown/papers/ps/sedna.pdf </ref> | + | 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. <ref>[http://www.gps.caltech.edu/%7Embrown/papers/ps/sedna.pdf Discovery of a candidate inner Oort cloud planetoid] - caltech.edu</ref> |
| − | [[Quaoar]] and [[90377 Sedna]] are two solar system objects discovered in this way by [[Michael E. Brown]] and others at CalTech using the [[Palomar Observatory]]’s [[Samual Oschin 48 inch Schmidt telescope]] 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. <ref>http://www.space.com/scienceastronomy/quaoar_discovery_021007.html</ref> <http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html</ref> | + | [[Quaoar]] and [[90377 Sedna]] are two solar system objects discovered in this way by [[Michael E. Brown]] and others at CalTech using the [[Palomar Observatory]]’s [[Samual Oschin 48 inch Schmidt telescope]] 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. <ref>[http://www.space.com/scienceastronomy/quaoar_discovery_021007.html Discovery: Largest Solar System Object Since Pluto] By Robert Roy Britt.</ref> <ref><[http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html Planet-Like Body Discovered at Fringes of Our Solar System] - NASA</ref> |
== Statistics == | == 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 [[statistics|statistical methods]] to compute data estimates and error ranges. | + | 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 [[statistics|statistical methods]] to compute data estimates and error ranges. |
| + | |||
| + | == In fiction == | ||
| + | |||
| + | * In the [[fiction]]al ''[[Star Trek: Voyager]]'', the '''Astrometrics''' lab is the [[set (drama)|set]] for various [[scene]]s. | ||
| + | * In the reimagined TV Show [[Battlestar Galactica]] an Astrometrics lab is stated in dialogue multiple times. | ||
== See also == | == See also == | ||
| Line 36: | Line 41: | ||
* [[Ephemeris]] | * [[Ephemeris]] | ||
* [[Equatorium]] | * [[Equatorium]] | ||
| − | * [[Gaia probe|Gaia Probe]] ( | + | * [[Gaia probe|Gaia Probe]] (ESA—Planned for 2009-14) |
| − | * [[Hipparcos|Hipparcos Space Astrometry Mission]] ( | + | * [[Hipparcos|Hipparcos Space Astrometry Mission]] (ESA—1989-93) |
* [[Spherical astronomy]] | * [[Spherical astronomy]] | ||
* [[Star cartography]] | * [[Star cartography]] | ||
==Notes== | ==Notes== | ||
| + | All links retrieved September 30, 2007. | ||
{{Reflist}} | {{Reflist}} | ||
==References== | ==References== | ||
| − | * Jean Kovalevsky and P. Kenneth Seidelman, '''Fundamentals of Astrometry''', Cambridge University Press, 2004, ISBN 0-521-64216-7. | + | * Kovalevsky, Jean. ''Modern Astrometry''. Berlin ; New York : Springer, 2002. ISBN 354042380X ISBN 9783540423805 |
| − | + | * Kovalevsky, Jean and P. Kenneth Seidelman, '''Fundamentals of Astrometry''', Cambridge University Press, 2004, ISBN 0-521-64216-7. | |
| − | + | * Walter, Hans G.''Astrometry of fundamental catalogues : the evolution from optical to radio reference frames''. Berlin ; New York : Springer, 2000. ISBN 3540674365 ISBN 9783540674368 | |
| − | |||
| − | |||
| − | |||
| − | * Walter, Hans G | ||
| − | |||
| − | |||
| − | == | + | ==External Links== |
| − | + | All links retrieved September 30, 2007. | |
| − | * | + | * {{cite web | url = http://www.astro.virginia.edu/~rjp0i/museum/engines.html | title = Hall of Precision Astrometry | publisher = University of Virginia Department of Astronomy}} |
| − | * | + | * [http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html Planet-Like Body Discovered at Fringes of Our Solar System] - NASA |
| + | * [http://www.space.com/scienceastronomy/quaoar_discovery_021007.html Discovery: Largest Solar System Object Since Pluto] By Robert Roy Britt | ||
| + | * [http://www.gps.caltech.edu/~mbrown Mike Brown's CalTech Home Page] | ||
| + | * [http://www.gps.caltech.edu/%7Embrown/papers/ps/sedna.pdf Scientific Paper describing Sedna's discovery] | ||
| + | * [http://www.rssd.esa.int/index.php?project=HIPPARCOS The Hipparcos Space Astrometry Mission] - ESA | ||
{{Astronomy-footer}} | {{Astronomy-footer}} | ||
Revision as of 22:42, 30 September 2007
Astrometry is the branch of astronomy that relates to precise measurements and explanations of the positions and movements of stars 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 and physical origin of our Solar System and our Galaxy, the Milky Way.
History
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. This can be dated back to Hipparchus, who around 190 B.C.E. used the catalogue of his predecessors Timocharis and Aristillus to discover the earth’s precession. In doing so, he also invented the brightness scale still in use today. [1]
James Bradley first tried to measure stellar parallaxes in 1729. The stellar movement proved too insignificant for his telescope, but he instead discovered the aberration of light and the nutation of the Earth’s axis. His cataloging of 3222 stars was refined in 1807 by Friedrich Bessel, the father of modern astrometry. He made the first measurement of stellar parallax: 0.3 arcsec for the binary star 61 Cygni.
Being very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century. Automated plate-measuring machines and more sophisticated computer technology of the 1960s allowed for larger compilations of star catalogues to be achieved more efficiently. In the 1980s, charge-coupled devices (CCDs) replaced photographic plates and reduced optical uncertainties to one milliarcsecond. This technology made astrometry less expensive, opening the field to an amateur audience.
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. Operated from 1989 to 1993, Hipparcos measured large and small angles on the sky with much greater precision than any previous optical telescopes. During its 4-year run, the positions, parallaxes, and proper motions of 118,218 stars were determined with an incredible degree of accuracy. A new catalogue “Tycho” drew together a database of 1,058,332 to within 20-30 mas. Additional catalogues were compiled for the 23,882 double/multiple stars and 11,597 variable stars also analyzed during the Hipparcos mission.[2]
Today, the catalogue most often used is USNO-B1.0, an all-sky catalogue that tracks proper motions, positions, magnitudes and other characteristics for over one billion stellar objects. During the past 50 years, 7,435 Schmidt plates were used to complete several sky surveys that make the data in USNO-B1.0 accurate to within 0.2 arcseconds. [3]
Applications
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.
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 (SIM PlanetQuest) 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.
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. [4]
Quaoar and 90377 Sedna are two solar system objects discovered in this way by Michael E. Brown and others at CalTech using the Palomar Observatory’s Samual Oschin 48 inch Schmidt telescope 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. [5] [6]
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 to compute data estimates and error ranges.
In fiction
- In the fictional Star Trek: Voyager, the Astrometrics lab is the set for various scenes.
- In the reimagined TV Show Battlestar Galactica an Astrometrics lab is stated in dialogue multiple times.
See also
- Astrometric binary
- Ephemeris
- Equatorium
- Gaia Probe (ESA—Planned for 2009-14)
- Hipparcos Space Astrometry Mission (ESA—1989-93)
- Spherical astronomy
- Star cartography
Notes
All links retrieved September 30, 2007.
- ↑ Hans G. Walter, Astrometry of fundamental catalogues : the evolution from optical to radio reference frames. Berlin ; New York : Springer, 2000. ISBN 3540674365 ISBN 9783540674368
- ↑ The Hipparcos Space Astrometry Mission - ESA
- ↑ Jean Kovalevsky, Modern Astrometry. Berlin ; New York : Springer, 2002. ISBN 354042380X ISBN 9783540423805
- ↑ Discovery of a candidate inner Oort cloud planetoid - caltech.edu
- ↑ Discovery: Largest Solar System Object Since Pluto By Robert Roy Britt.
- ↑ <Planet-Like Body Discovered at Fringes of Our Solar System - NASA
ReferencesISBN links support NWE through referral fees
- Kovalevsky, Jean. Modern Astrometry. Berlin ; New York : Springer, 2002. ISBN 354042380X ISBN 9783540423805
- Kovalevsky, Jean and P. Kenneth Seidelman, Fundamentals of Astrometry, Cambridge University Press, 2004, ISBN 0-521-64216-7.
- Walter, Hans G.Astrometry of fundamental catalogues : the evolution from optical to radio reference frames. Berlin ; New York : Springer, 2000. ISBN 3540674365 ISBN 9783540674368
External Links
All links retrieved September 30, 2007.
- Hall of Precision Astrometry. University of Virginia Department of Astronomy.
- Planet-Like Body Discovered at Fringes of Our Solar System - NASA
- Discovery: Largest Solar System Object Since Pluto By Robert Roy Britt
- Mike Brown's CalTech Home Page
- Scientific Paper describing Sedna's discovery
- The Hipparcos Space Astrometry Mission - ESA
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