proper motion

Luyten 726-8 is a binary star system that is one of Earth's nearest neighbors. One of its components is the well-known flare star UV Ceti (Luyten 726-8 B). Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, and in fact flare stars are sometimes called "UV Ceti variables". It goes through fairly extreme changes of brightness: for instance, in 1952, its brightness increased by 75 times in only 20 seco ...

Including:

• Luyten 726-8 - Discovery

Read more here: » Luyten 726-8: Encyclopedia - Luyten 726-8

Castor (α Gem / α Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum (Pollux). Castor and Pollux are the two "heavenly twin" stars that give the constellation Gemini (meaning "twins" in Latin) its name. Astronomically, Castor was discovered to be a visual binary in 1719, with the magnitude of its components being 2.8 and 2.0. The separation of ...

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Aries (Latin for Ram, symbol , Unicode ♈) is one of the constellations of the zodiac. It lies between Pisces to the west and Taurus to the east. Aries - Notable features. Aries' stars are rather faint except for α Ari (Hamal) and β Ari (Sharatan). Other important stars are γ Ari (Mesarthim) and δ Ari (Botein). Teegarden's star, in Aries, is one of our sun's closest neighbours. The Deep Photographic Guide to the Constellations: Aries, Aries Links on ...

Including:

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

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61 Cygni is a star in the constellation Cygnus. Though it is among the least conspicuous of stars visible in the night sky to an observer without an optical instrument, 61 Cygni attracted the attention of astronomers due to its large proper motion. The star is in fact a double star system. This system should not be confused with 16 Cygni, which includes a Sun-like star with a very eccentric planet. 61 Cygni - General information. 61 Cygni's proper motion is so great, relatively speaking, that its app ...

Including:

• 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 - 61 Cygni

A binary star system consists of two stars both orbiting around their barycenter. For each star, the other is its "companion star". The term "binary star" was apparently first coined by Sir William Herschel in 1802 to designate "a real double star — the union of two stars that are formed together in one system by the laws of attraction". Any two stars seen close to one another form a double star, the most famous being Mizar and Alcor in the Big Dipper. Odds are, though, that a double star is probably a foreground and b ...

Including:

• Binary star - Binary star classifications
• Binary star - Research findings
• Binary star - Binary star examples

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

Alpha Centauri (α Cen / α Centauri) is the brightest star system (a triple star system) in the southern constellation of Centaurus, and contains the fourth brightest star in the night sky, with an apparent visual magnitude of −0.01. It is famous in the Southern Hemisphere as the outermost “pointer” to the Southern Cross, but it is too far south to be visible in most of the northern hemisphere. To the naked eye, the two brightest components of the system are too close for the eye to ...

Including:

• 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

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Van Maanen's Star is a white dwarf, the second such star discovered and the third closest one to the Sun after Sirius B and Procyon B. It is located 14.4 light years from the Sun in the constellation Pisces, and has a relatively high proper motion of 2.98" annually. It is far too faint to be seen with the naked eye. Its mass is about 7/10 that of the Sun, but its diameter and brightness are far less. ...

Including:

• Van Maanen's star - External link

Read more here: » Van Maanen's star: Encyclopedia - Van Maanen's star

Ayanamsha is a term used in astrology. It is defined as the angle by which the sidereal ecliptic longitude of a celestial body is lesser than its tropical ecliptic longitude. The sidereal ecliptic longitude of a celestial body is its longitude on the ecliptic defined with respect to the "fixed" stars. The tropical ecliptic longitude of a celestial body is its longitude on the ecliptic defined ...

Including:

• Ayanamsha - Different methods of determining the ayanamsha

Read more here: » Ayanamsha: Encyclopedia - Ayanamsha

In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some of the more frequently quoted ones. Most of the recent catalogues are available in electronic format and can be freely downloaded from NASA's Astronomical Data Center and other places (see links at end). Star catalogue - Historical catalogues. The world's first star catalogue was made by Gan De ...

Including:

• 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 - Star catalogue

Sir Wilhelm Friedrich Herschel, FRS (Hanover, November 15, 1738 – August 25, 1822 Slough, then in Buckinghamshire now in Berkshire) was a German-born British astronomer and composer who became famous for discovering the planet Uranus, and made many other astronomical discoveries. William Herschel - Biography. 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 ...

Including:

• 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 - William Herschel

A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and the Earth, obscuring a small portion of the Sun's disc. During a transit, Venus can be seen from the Earth as a small black disc moving across the face of the Sun. The duration of such transits is usually measured in hours (the transits of 2004 and 2012 last about six hours). A transit is similar to a solar eclipse by the Moon, but, although the diameter of Venus is almost 4 times that of the Moon, Venus appears much smaller because ...

Including:

• 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

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For the software company, see Cygnus Solutions. Cygnus (from the Latin word Cygnus, meaning "swan") is a northern constellation. It was one of Ptolemy's 48 constellations, and is also one of the 88 modern constellations. Because of the pattern of its main stars, it is sometimes known as the Northern Cross (in contrast to the Southern Cross). The bird extends over the Milky Way, appearing to fly south. Cygnus constellation - Notable features. Cygnus contains several bright ...

Including:

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

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Epsilon Indi is held by many Star Trek fans to be the home star system of the Andorian race. The star system also made an appearance in the original Star Trek episode And the Children Shall Lead, where Epsilon Indi was the home star system to an evil energy being known as "Gorgan". In the Worldwar books by Harry Turtledove, Epsilon Indi is one of the subject star systems ("Halless") of the alien Race. ...

See also:

Epsilon Indi, Epsilon Indi - Epsilon Indi in fiction

Read more here: » Epsilon Indi: Encyclopedia II - Epsilon Indi - Epsilon Indi in fiction

The bulk of the stars in a spiral galaxy are located either close to a single plane (the Galactic plane) in more or less conventional circular orbits around the center of the galaxy (the galactic core), or in a spheroidal galactic bulge around the galactic core. However, some stars inhabit a spheroidal halo surrounding the galaxy. The orbital behaviour of these stars is as yet disputed, but they may describe retrograde and/or highly inclined orbits, or not to move in regular orbits at all. Halo stars may be acquired from small galaxies which ...

See also:

Galactic halo, Galactic halo - Halo stars, Galactic halo - Halo dark matter

Read more here: » Galactic halo: Encyclopedia II - Galactic halo - Halo stars

The first Herbig-Haro object was observed in the late 19th century by Burnham, when he looked at the star T Tauri with the 36-inch refracting telescope at Lick Observatory and noted a small patch of nebulosity nearby. However, it was catalogued merely as an emission nebula, later becoming known as Burnham's Nebula, and was not recognised as a distinct class of object. However, T Tauri was found to be a very young and variable star, and is the prototype of the class of similar objects known as T Tauri stars which have yet to reach a state of equilibrium between gravitati ...

See also:

Herbig-Haro object, Herbig-Haro object - Discovery and history of observations, Herbig-Haro object - Physical characteristics, Herbig-Haro object - Numbers and distribution, Herbig-Haro object - Proper motions and variability, Herbig-Haro object - Source stars

Read more here: » Herbig-Haro object: Encyclopedia II - Herbig-Haro object - Discovery and history of observations

The term "binary star" was apparently coined by Sir William Herschel in 1802 to designate "a real double star — the union of two stars that are formed together in one system by the laws of attraction". Any two closely-spaced stars might appear to be a double star, the most famous case being Mizar and Alcor in the Big Dipper. Odds are, though, that a double star is probably a foreground/background star pair that only looks like a binary system — the two stars are, in reality, widely separated in space but just happen ...

See also:

Binary star, Binary star - Background, 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 - Background

The most prominent open clusters such as the Pleiades have been known and recognised as groups of stars since antiquity. Others were known as fuzzy patches of light, but had to wait until the invention of the telescope to be resolved into their constituent stars. Telescopic observations revealed two distinct types of clusters, one of which contained thousands of stars in a regular spherical distribution and was found preferentially towards the centre of the Milky Way, and the other of which consisted of a generally sparser population of star ...

See also:

Open cluster, Open cluster - Historical observations, Open cluster - Formation, Open cluster - Morphology and classification, Open cluster - Numbers and distribution, Open cluster - Stellar composition, Open cluster - Eventual fate, Open cluster - Studying stellar evolution, Open cluster - Open clusters and the astronomical distance scale

Read more here: » Open cluster: Encyclopedia II - Open cluster - Historical observations

Most bright naked eye stars have traditional names, most of which derive from Arabic, but a few from Latin. See List of traditional star names for a list of some of these names. There are a number of problems with these names however: Spellings are often not standardized (Almach or Almaach or Almak or Alamak) Many stars have more than one name of roughly equal popularity (Mirfak or Algenib or Alcheb; Regor or Suhail al Muhlif; Alkaid or Benetnasch; Gemma or Alphecca; Alpheratz and Sirrah) Because of impr ...

See also:

Star designation, Star designation - Proper names, Star designation - Bayer letters, Star designation - Flamsteed numbers, Star designation - Variable designations, Star designation - Catalogue numbers, Star designation - Unofficial names, Star designation - Eponyms

Read more here: » Star designation: Encyclopedia II - Star designation - Proper names

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. ...

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

Even though the companion is invisible, the characteristics of the system can be determined from the observations using Kepler's laws. The following equation gives the relation between the masses and the amount of motion observed: where: m1 = mass of the star in solar masses. m2 = mass of the hidden companion in solar masses. a1 = semi-major axis of the star's orbit about the mass-center in seconds of arc. p = parallax of the binary system in seconds of arc.< ...

See also:

Astrometric binary, Astrometric binary - Mathematical formulation, Astrometric binary - Methods of observation

Read more here: » Astrometric binary: Encyclopedia II - Astrometric binary - Mathematical formulation