proper motion

The key instrument of nearly all modern observational astronomy is the telescope. This serves the dual purposes of gathering more light so that very faint objects can be observed, and magnifying the image so that small and distant objects can be observed. The optics used in a telescope have very exacting requirements which require great precision in their construction. Typical requirements for grinding and polishing a curved mirror, for example, require the surface to be within a f ...

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Observational astronomy, Observational astronomy - Unaided eye, Observational astronomy - Telescopes, Observational astronomy - Optical telescopes, Observational astronomy - Other instruments, Observational astronomy - Observation tools, Observational astronomy - Observing, Observational astronomy - Related lists

Read more here: » Observational astronomy: Encyclopedia II - Observational astronomy - Observation tools

Bayer and Flamsteed covered only a few thousand stars between them. In theory, full-sky catalogues try to list every star in the sky. There are, however, literally hundreds of millions, even billions of stars resolvable by telescopes, so this is an impossible goal; these kind of catalogs generally try to get every star brighter than a given magnitude. Star catalogue - HD/HDE. Main articles: Henry Draper Catalogue, See also:

Star catalogue, Star catalogue - Historical catalogues, Star catalogue - Full-sky catalogues, Star catalogue - HD/HDE, Star catalogue - SAO, Star catalogue - BD/CD/CPD, Star catalogue - AC, Star catalogue - USNO-B1.0, Star catalogue - Specialized catalogues, Star catalogue - ADS, Star catalogue - BS BSC HR, Star catalogue - GJ Gliese Gl, Star catalogue - GCTP, Star catalogue - HIP, Star catalogue - Proper motion catalogues

Read more here: » Star catalogue: Encyclopedia II - Star catalogue - Full-sky catalogues

There are currently six methods of detecting extrasolar planets which are too faint relative to their much brighter host stars to be directly detected by present conventional optical means. The planned Space Interferometry Mission, Terrestrial Planet Finder and Darwin would all try to examine planets in a more direct fashion. Extrasolar planet - Pulsar timing. The first method used to discover extra-solar planets was to observe anomalies in the regularity of pulses from a pulsar. This led to the 'di ...

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Extrasolar planet, Extrasolar planet - History of detection, Extrasolar planet - Methods of detection, Extrasolar planet - Pulsar timing, Extrasolar planet - Astrometry, Extrasolar planet - Radial velocity, Extrasolar planet - Gravitational microlensing, Extrasolar planet - Transit method, Extrasolar planet - Circumstellar disks, Extrasolar planet - Direct observation, Extrasolar planet - Solar system formation processes, Extrasolar planet - Notable extrasolar planets, Extrasolar planet - Table of extremes

Read more here: » Extrasolar planet: Encyclopedia II - Extrasolar planet - Methods of detection

The Triangulum Galaxy was probably discovered by Giovanni Batista Hodierna before 1654, who may have grouped it together with open cluster NGC 752. It was independently discovered by Charles Messier in 1764, who catalogued it as M33 on August 25. M33 was also catalogued independently by William Herschel on September 11, 1784, who assigned it the number H V.17. It was among the first "spiral Nebulae" identified as such by Lord Rosse. Herschel also cataloged The Triangulum Galaxy's brightest and largest H II region (diffuse emission neb ...

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Triangulum Galaxy, Triangulum Galaxy - General information, Triangulum Galaxy - References in fiction, Triangulum Galaxy - External link

Read more here: » Triangulum Galaxy: Encyclopedia II - Triangulum Galaxy - General information

When including fainter stars, visible to the naked eye, the area resembles the head of a ram, having a general herbivore head shape and a spiral horn. In Greek mythology, this is believed to represent the ram which carried Athamas's son Phrixus and daughter Helle to Colchis to escape their stepmother Ino. Helle fell off into the sea which later became the Hellespont. On reaching safety, Phrixis (rather ungratefully) sacrificed the ram and hung its fleece in the Grove of Ares, where it turned to gold and later became the quest of Jason and the Argonauts. It appears that Babylonians, Greeks, Persians and Egyptians all agreed on the name ...

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Aries, Aries - Notable features, Aries - Notable deep sky objects, Aries - Mythology, Aries - Astrology, Aries - Notable and named stars

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The first known pulsar was discovered by Jocelyn Bell and Antony Hewish in 1967 while they were using a radio array to study the scintillation of quasars. They found a very regular signal, consisting of pulses of radiation at a rate of one in every few seconds. Terrestrial origin of the signal was ruled out because the time it took the object to reappear was a sidereal day instead of a solar day. The original name given to the object was "LGM-1", short for "Little Green Men", a comical name for intelligent beings of extraterrestrial o ...

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Rotation-powered pulsar, Rotation-powered pulsar - History, Rotation-powered pulsar - Theory, Rotation-powered pulsar - Importance, Rotation-powered pulsar - Significant pulsars

Read more here: » Rotation-powered pulsar: Encyclopedia II - Rotation-powered pulsar - History

Viewed from near Alpha Centauri, the sky (other than the Alpha Centauri stars) would appear very much as it does to observers on Earth, with most of the constellations such as Ursa Major and Orion being almost unchanged. However, Centaurus would be missing its brightest star and our Sun would appear as a 0.5-magnitude star in Cassiopeia. Roughly speaking, the \/\/ of Cassiopeia would become a /\/\/, with the Sun at the leftmost end, closest to ε Cassiopeiae. The position can easily be plotted as RA 02h39m35s, dec +6 ...

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Alpha Centauri, Alpha Centauri - Names, Alpha Centauri - System components, Alpha Centauri - Possibility of planet formation, Alpha Centauri - Sky appearance from Alpha Centauri, Alpha Centauri - Apparent movement, Alpha Centauri - Alpha Centauri in fiction

Read more here: » Alpha Centauri: Encyclopedia II - Alpha Centauri - Sky appearance from Alpha Centauri

61 Cygni's proper motion is so great, relatively speaking, that its apparent position shifts by an amount equal to the width of the full moon in a mere 150 years. This large proper motion, the largest known for any star at the time, made 61 Cygni a candidate for the determination of its distance by the method of parallax when the quality of astronomical observations first made this possible. The star therefore has the distinction of being the first star (excluding the Sun) to have its distance determined. This was accomplished by Friedrich Wilhelm Bessel in 1838 who arrived at a figure close to t ...

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61 Cygni, 61 Cygni - General information, 61 Cygni - The binary system, 61 Cygni - 61 Cygni B's planet, 61 Cygni - 61 Cygni in Fiction

Read more here: » 61 Cygni: Encyclopedia II - 61 Cygni - General information

Apart from its rarity, the original scientific interest in observing a transit of Venus was that it could be used to determine the size of the solar system. The technique is to make precise observations of the slight difference in the time of either the start or the end of the transit from widely separated points on the Earth. The distance between the points on the Earth can then be used as a yard stick for the distance to Venus and the Sun. See "parallax". Although by the 17th century astronomers could calculate each planet's relativ ...

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Transit of Venus, Transit of Venus - Conjunctions of Venus with the Sun, Transit of Venus - Scientific interest in transits, Transit of Venus - Past and future transits, Transit of Venus - Observing transits of Venus, Transit of Venus - Grazing transits of Venus, Transit of Venus - Simultaneous transits, Transit of Venus - Cultural meaning

Read more here: » Transit of Venus: Encyclopedia II - Transit of Venus - Scientific interest in transits

Apart from its rarity, the original scientific interest in observing a transit of Venus was that it could be used to determine the size of the solar system. The technique is to make precise observations of the slight difference in the time of either the start or the end of the transit from widely separated points on the Earth. The distance between the points on the Earth can then be used as a yard stick for the distance to Venus and the Sun. See "parallax". Although by the 17th century astronomers could calculate each planet's relativ ...

See also:

Transit of Venus, Transit of Venus - Conjunctions of Venus with the Sun, Transit of Venus - Scientific interest in transits, Transit of Venus - Past and future transits, Transit of Venus - Grazing transits of Venus, Transit of Venus - Simultaneous transits, Transit of Venus - Cultural meaning

Read more here: » Transit of Venus: Encyclopedia II - Transit of Venus - Scientific interest in transits

As Friedrich Wilhelm Herschel in Hanover, Germany, one of ten children (of which four died very young). In 1755 the Hanoverian Guards regiment in whose band William and his brother Jacob were engaged was ordered to England. At the time, the crowns of England and Hanover were united under George II. He learned English quickly and, at age nineteen, he changed his name to Frederick William Herschel. He became a successful music teacher and bandleader, played the organ and the oboe, and composed numerous musical works, most ...

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William Herschel, William Herschel - Biography, William Herschel - Other astronomical work, William Herschel - Discovery of infrared radiation, William Herschel - Named after Herschel

Read more here: » William Herschel: Encyclopedia II - William Herschel - Biography

During the past 200 years a large amount of research has been carried out on binary stars leading to some general conclusions. It is believed that at least a quarter of all stars are at least binary systems, with as many as 10% of these systems containing more than two stars (ternary etc.). There is a direct correlation between the period of revolution of a binary star and the eccentricity of its orbit, with systems of short period having smaller eccentricity. Binary stars may be found with any conceivable separation, from pair ...

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Binary star, Binary star - Binary star classifications, Binary star - Research findings, Binary star - Binary star examples, Binary star - Binary stars in fiction

Read more here: » Binary star: Encyclopedia II - Binary star - Research findings

During the past 200 years a large amount of research has been carried out on binary stars leading to some general conclusions. It is believed that at least a quarter of all stars are at least binary systems, with as many as 10% of these systems containing more than two stars (ternary etc.). There is a direct correlation between the period of revolution of a binary star and the eccentricity of its orbit, with systems of short period having smaller eccentricity. Binary stars may be found with any conceivable separation, from pair ...

See also:

Binary star, Binary star - Binary star classifications, Binary star - Research findings, Binary star - Binary star examples

Read more here: » Binary star: Encyclopedia II - Binary star - Research findings

Bayer and Flamsteed covered only a few thousand stars between them. In theory, full-sky catalogues try to list every star in the sky. There are, however, literally hundreds of millions, even billions of stars resolvable by telescopes, so this is an impossible goal; these kind of catalogs generally try to get every star brighter than a given magnitude. Star catalogue - HD/HDE. The Henry Draper Catalogue was published in the period 1918–1924. It covers the whole sky down to about ninth or tenth magnitude, ...

See also:

Star catalogue, Star catalogue - Historical catalogues, Star catalogue - Full-sky catalogues, Star catalogue - HD/HDE, Star catalogue - SAO, Star catalogue - BD/CD/CPD, Star catalogue - AC, Star catalogue - USNO-B1.0, Star catalogue - Specialized catalogues, Star catalogue - ADS, Star catalogue - BS BSC HR, Star catalogue - GJ Gliese Gl, Star catalogue - GCTP, Star catalogue - HIP, Star catalogue - Proper motion catalogues

Read more here: » Star catalogue: Encyclopedia II - Star catalogue - Full-sky catalogues

The declination of all celestial objects vary over time, in different periods. Declination - Sun. The declination of the sun (Sun Dec) is the angle between the rays of the sun and the plane of the earth equator. Since the angle between the earth axis and the plane of the earth orbit is nearly constant, Sun Dec varies with the seasons and its period is one year, that is the time needed by t ...

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Declination, Declination - Varying declination, Declination - Sun, Declination - Moon, Declination - Stars

Read more here: » Declination: Encyclopedia II - Declination - Varying declination

Halley was born at Haggerston, London, the son of a wealthy soapboiler. He studied at St Paul's School, and then from 1673 at The Queen's College, Oxford. Whilst an undergraduate he published papers on the Solar System and sunspots. On leaving Oxford, in 1676, he visited the south Atlantic island of St. Helena with the intention of studying stars from the Southern Hemisphere. He returned to England in November 1678. In the following year he published Catalogus Stellarum Australium which included details of 341 southern stars. T ...

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Edmond Halley, Edmond Halley - Biography and career, Edmond Halley - Named after Halley

Read more here: » Edmond Halley: Encyclopedia II - Edmond Halley - Biography and career

Cygnus contains several bright stars. Deneb, α Cygni, is an extremely brilliant star, very prominent despite its distance (1 800 light years). The blue supergiant forms the swan's tail, the upper end of the Northern Cross, and one of the vertices of the so-called "Summer Triangle". Albireo, β Cygni, is at the swan's beak. It is one of the most beautiful double stars of the sky, a golden star easily dist ...

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Cygnus constellation, Cygnus constellation - Notable features, Cygnus constellation - Notable deep sky objects, Cygnus constellation - History and mythology, Cygnus constellation - Stars, Cygnus constellation - In Art and Literature

Read more here: » Cygnus constellation: Encyclopedia II - Cygnus constellation - Notable features

At present, binary stars are classified into four types according to their observable properties: visual binaries spectroscopic binaries eclipsing binaries astrometric binaries Any star can belong to several of these classes, e.g., several spectroscopic binaries are also eclipsing binaries. Another three-category classification is based on the distance of the stars, relative to their sizes : detached binaries ...

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Binary star, Binary star - Binary star classifications, Binary star - Research findings, Binary star - Binary star examples

Read more here: » Binary star: Encyclopedia II - Binary star - Binary star classifications

It bears the proper name Rigil Kentaurus (often shortened to Rigil Kent), derived from the Arabic phrase Al Rijl al Kentaurus, meaning "foot of the centaur," but is nonetheless usually referred to by its Bayer designation Alpha Centauri. Another alternative name is Toliman. It is also sometimes known as Bungula, possibly from the Latin word ungula meaning "hoof". It and Beta Centauri (which is close to Alpha Centauri in angular distance as seen from the Earth, but is actually many light-years ...

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Alpha Centauri, Alpha Centauri - Names, Alpha Centauri - System components, Alpha Centauri - Possibility of planet formation, Alpha Centauri - Sky appearance from Alpha Centauri, Alpha Centauri - Apparent movement, Alpha Centauri - Alpha Centauri in fiction

Read more here: » Alpha Centauri: Encyclopedia II - Alpha Centauri - Names

See the list of stars with confirmed extrasolar planets for a list of confirmed observations. Extrasolar planet - Table of extremes. Note: upper limit for planets is 11 MJupiter (deuterium fusion limit - lower limit for brown dwarfs) Note: PSR 1257+12 system may include possible asteroidal object, but it is not massive enough to qualify as a planet Note: only radii of transiting planets are known Note 1: Th ...

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Extrasolar planet, Extrasolar planet - History of detection, Extrasolar planet - Methods of detection, Extrasolar planet - Pulsar timing, Extrasolar planet - Astrometry, Extrasolar planet - Radial velocity, Extrasolar planet - Gravitational microlensing, Extrasolar planet - Transit method, Extrasolar planet - Circumstellar disks, Extrasolar planet - Direct observation, Extrasolar planet - Solar system formation processes, Extrasolar planet - Notable extrasolar planets, Extrasolar planet - Table of extremes

Read more here: » Extrasolar planet: Encyclopedia II - Extrasolar planet - Notable extrasolar planets

There is general agreement that what we observe as a pulse is what happens when a beam of radiation points in our direction, once for every rotation of the neutron star. The origin of the beam is related to the misalignment of the rotation axis and the axis of the magnetic field of the star. The beam is emitted from the poles of the neutron star's magnetic field, which may be offset from the rotational poles by a wide angle. The source of energy of the beam is the rotational energy of the neutron star. The rotat ...

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Rotation-powered pulsar, Rotation-powered pulsar - History, Rotation-powered pulsar - Theory, Rotation-powered pulsar - Importance, Rotation-powered pulsar - Significant pulsars

Read more here: » Rotation-powered pulsar: Encyclopedia II - Rotation-powered pulsar - Theory