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29-550: The first version of this catalog was published in 1989. The first catalog was created by digitizing photographic plates produced by the Palomar Schmidt Quick-V survey for the northern hemisphere and the UK Schmidt SERC-J survey for the southern hemisphere. This catalog contains objects in the magnitude range 7-16 and the classification was biased to prevent the use of a non-stellar object as a guide star. The photometry

58-661: A Hubble sky region code. A significant expansion of the catalog, Guide Star Catalog II, was published in 2008. The Guide Star Catalog II (GSC-II) was compiled by the Catalog and Surveys branch of the Space Telescope Science Institute and the astrometry team of the Astronomical Observatory of Torino (Italy). It has entries for 945,592,683 stars, and has positions, classifications, and magnitudes for 455,851,237 stars. The latest revision of this version (2.3.4)

87-497: A degree away from the positions charted by the ancient Greek astronomer Hipparchus roughly 1850 years earlier. The lesser meaning of "proper" used is arguably dated English (but neither historic, nor obsolete when used as a postpositive , as in "the city proper") meaning "belonging to" or "own". "Improper motion" would refer to perceived motion that is nothing to do with an object's inherent course, such as due to Earth's axial precession , and minor deviations, nutations well within

116-476: Is 90 km/s and its radial velocity is 111 km/s (perpendicular (at a right, 90° angle), which gives a true or "space" motion of 142 km/s. True or absolute motion is more difficult to measure than the proper motion, because the true transverse velocity involves the product of the proper motion times the distance. As shown by this formula, true velocity measurements depend on distance measurements, which are difficult in general. In 1992 Rho Aquilae became

145-445: Is based on a photoelectric sequence (9-15th mag) near the center of each Schmidt plate. Stellar photometry was performed in a manner that would systematically reject galaxies. Astrometry was determined using the AGK3 , SAOC or CPC catalog stars depending on plate declination. Although the relative astrometry (required for HST) is about 0.3 arc seconds, there are known systematic errors near

174-531: Is caused by the movement of the stars relative to the Sun and Solar System . The Sun travels in a nearly circular orbit (the solar circle ) about the center of the galaxy at a speed of about 220 km/s at a radius of 8,000 parsecs (26,000 ly) from Sagittarius A* which can be taken as the rate of rotation of the Milky Way itself at this radius. Any proper motion is a two-dimensional vector (as it excludes

203-562: Is computed as the total proper motion ( μ ). It has dimensions of angle per time , typically arcseconds per year or milliarcseconds per year. Knowledge of the proper motion, distance, and radial velocity allows calculations of an object's motion from the Solar System's frame of reference and its motion from the galactic frame of reference – that is motion in respect to the Sun, and by coordinate transformation , that in respect to

232-547: Is designated μ α* . For example, the proper motion results in right ascension in the Hipparcos Catalogue (HIP) have already been converted. Hence, the individual proper motions in right ascension and declination are made equivalent for straightforward calculations of various other stellar motions. The position angle θ is related to these components by: Motions in equatorial coordinates can be converted to motions in galactic coordinates . For most stars seen in

261-459: Is given by the Pythagorean theorem : where δ is the declination. The factor in cos δ accounts for the widening of the lines (hours) of right ascension away from the poles, cos δ , being zero for a hypothetical object fixed at a celestial pole in declination. Thus, a co-efficient is given to negate the misleadingly greater east or west velocity (angular change in α ) in hours of Right Ascension

290-616: Is in active use for accurately positioning the Hubble Space Telescope. Astronomische Gesellschaft Katalog The Astronomische Gesellschaft Katalog (AGK) is an astrometric star catalogue of the Northern hemisphere. It was published in 3 versions from 1890 until 1975, named AGK1, AGK2 and AGK3. Compilation for the first version, Astronomische Gesellschaft Katalog 1 AGK1 , was started in 1867, directed by Friedrich Argelander and published between 1890 (three sections from

319-590: Is one source of such images. In the past, searches for high proper motion objects were undertaken using blink comparators to examine the images by eye. More modern techniques such as image differencing can scan digitized images, or comparisons to star catalogs obtained by satellites. As any selection biases of these surveys are well understood and quantifiable, studies have confirmed more and inferred approximate quantities of unseen stars – revealing and confirming more by studying them further, regardless of brightness, for instance. Studies of this kind show most of

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348-530: Is the astrometric 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 . The components for proper motion in the equatorial coordinate system (of a given epoch , often J2000.0 ) are given in the direction of right ascension ( μ α ) and of declination ( μ δ ). Their combined value

377-551: The Milky Way . Over the course of centuries, stars appear to maintain nearly fixed positions with respect to each other, so that they form the same constellations over historical time. As examples, both Ursa Major in the northern sky and Crux in the southern sky, look nearly the same now as they did hundreds of years ago. However, precise long-term observations show that such constellations change shape, albeit very slowly, and that each star has an independent motion . This motion

406-719: The Triangulum Galaxy M33, the third largest and only ordinary spiral galaxy in the Local Group, located 0.860 ± 0.028 Mpc beyond the Milky Way. The motion of the Andromeda Galaxy was measured in 2012, and an Andromeda–Milky Way collision is predicted in about 4.5 billion years. Proper motion of the NGC 4258 (M106) galaxy in the M106 group of galaxies was used in 1999 to find an accurate distance to this object. Measurements were made of

435-456: The Bonn part then directed by Ernst Arnold Kohlschütter . The third version, AGK3 , was started in 1956 and published in 1975. It contains 183,145 stars north of declination –2° with mean positional errors of ±0.13 " and mean proper motion errors of ±0.009"/year. This astronomical catalog article is a stub . You can help Misplaced Pages by expanding it . Proper motion Proper motion

464-486: The GSC limiting magnitude. In addition, many of the false objects due to artifacts around the halos and diffraction spikes of the bright stars were identified and corrected as well as a number of reported errors. A number of astrographic plates centered on southern hemisphere bright stars (of magnitude less than 3) were also processed and added to the catalog. This was the version used by HST operations prior to cycle 15. Version 1.2

493-398: The angular changes per year in the star's right ascension ( μ α ) and declination ( μ δ ) with respect to a constant epoch . The components of proper motion by convention are arrived at as follows. Suppose an object moves from coordinates (α 1 , δ 1 ) to coordinates (α 2 , δ 2 ) in a time Δ t . The proper motions are given by: The magnitude of the proper motion μ

522-519: The cluster. Stellar proper motions have been used to infer the presence of a super-massive black hole at the center of the Milky Way. This now confirmed to exist black hole is called Sgr A* , and has a mass of 4.3 × 10   M ☉ (solar masses). Proper motions of the galaxies in the Local Group are discussed in detail in Röser. In 2005, the first measurement was made of the proper motion of

551-604: The component as to the direction of the line of sight) and it bears two quantities or characteristics: its position angle and its magnitude . The first is the direction of the proper motion on the celestial sphere (with 0 degrees meaning the motion is north, 90 degrees meaning the motion is east, (left on most sky maps and space telescope images) and so on), and the second is its magnitude, typically expressed in arcseconds per year (symbols: arcsec/yr, as/yr, ″/yr, ″ yr ) or milliarcseconds per year (symbols: mas/yr, mas yr ). Proper motion may alternatively be defined by

580-545: The first star to have its Bayer designation invalidated by moving to a neighbouring constellation – it is now in Delphinus . Stars with large proper motions tend to be nearby; most stars are far enough away that their proper motions are very small, on the order of a few thousandths of an arcsecond per year. It is possible to construct nearly complete samples of high proper motion stars by comparing photographic sky survey images taken many years apart. The Palomar Sky Survey

609-407: The further it is towards the imaginary infinite poles, above and below the earth's axis of rotation, in the sky. The change μ α , which must be multiplied by cos δ to become a component of the proper motion, is sometimes called the "proper motion in right ascension", and μ δ the "proper motion in declination". If the proper motion in right ascension has been converted by cos δ , the result

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638-467: The largest proper motion of all stars, moving at 10.3″ yr . Large proper motion usually strongly indicates an object is close to the Sun. This is so for Barnard's Star, about 6 light-years away. After the Sun and the Alpha Centauri system, it is the nearest known star. Being a red dwarf with an apparent magnitude of 9.54, it is too faint to see without a telescope or powerful binoculars. Of

667-463: The nearest stars are intrinsically faint and angularly small, such as red dwarfs . Measurement of the proper motions of a large sample of stars in a distant stellar system, like a globular cluster, can be used to compute the cluster's total mass via the Leonard-Merritt mass estimator . Coupled with measurements of the stars' radial velocities , proper motions can be used to compute the distance to

696-466: The observatories at Oslo, Helsinki, and Neuchâtel Observatory ) and 1924 (final section: Algiers Observatory ), listing 200 000 stars down to ninth magnitude . The second version, AGK2 , was started in the 1920s, and published between 1951 and 1958 using photographic data obtained from the Bonn and Hamburg Observatories . Karl Friedrich Küstner was involved in the planning for star catalog AGK2 with

725-536: The plate edges of 1 to 2 arc seconds. The first revision of the catalog was published in 1992. The Tycho Input Catalog was created by the Hipparcos/Tycho international consortia in preparation for the Hipparcos satellite mission. They produced a catalog containing the best available data for all stars to magnitude 11. Adding the bright star data from this catalog to the GSC produced a complete all-sky catalog down to

754-471: The radial motion of objects in that galaxy moving directly toward and away from Earth, and assuming this same motion to apply to objects with only a proper motion, the observed proper motion predicts a distance to the galaxy of 7.2 ± 0.5 Mpc . Proper motion was suspected by early astronomers (according to Macrobius , c. AD 400) but a proof was not provided until 1718 by Edmund Halley , who noticed that Sirius , Arcturus and Aldebaran were over half

783-638: The sky, the observed proper motions are small and unremarkable. Such stars are often either faint or are significantly distant, have changes of below 0.01″ per year, and do not appear to move appreciably over many millennia. A few do have significant motions, and are usually called high-proper motion stars. Motions can also be in almost seemingly random directions. Two or more stars, double stars or open star clusters , which are moving in similar directions, exhibit so-called shared or common proper motion (or cpm.), suggesting they may be gravitationally attached or share similar motion in space. Barnard's Star has

812-426: The stars visible to the naked eye (conservatively limiting unaided visual magnitude to 6.0), 61 Cygni A (magnitude V= 5.20) has the highest proper motion at 5.281″ yr , discounting Groombridge 1830 (magnitude V= 6.42), proper motion: 7.058″ yr . A proper motion of 1 arcsec per year 1 light-year away corresponds to a relative transverse speed of 1.45 km/s. Barnard's Star's transverse speed

841-607: Was published in 2001. It was produced in collaboration with the Astronomisches Rechen-Institut in Heidelberg . This version reduces the plate-based position-dependent and magnitude-dependent systematic errors. The PPM and AC reference catalogs were used and absolute position errors have been reduced to between 0.3 and 0.4 arc seconds. When quoting a catalog entry, the format is GSC FFFFF-NNNNN , or alternately, GSCfffff0nnnnn (fffff0nnnnn). The F-sequence references

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