Star catalogue A star catalogue or star catalog, is an astronomical catalogue that lists stars.
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In astronomy , many stars are referred to by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, this article covers only some of the more quoted ones. Star catalogues were compiled by many different ancient people, including the Babylonians , Chinese and Arabs , they were sometimes accompanied by a star chart for illustration. Most modern catalogues are available in electronic format and can be downloaded from space agencies data centres.
Completeness and accuracy is described by the weakest apparent magnitude V and the accuracy of the positions. From their existing records, it is known that the ancient Egyptians recorded the names of only a few identifiable constellations and a list of thirty-six decans that were used as a star clock ; the Egyptians called the circumpolar star "the star that cannot perish" and, although they made no known formal star catalogues, they nonetheless created extensive star charts of the night sky which adorn the coffins and ceilings of tomb chambers.
Although the ancient Sumerians were the first to record the names of constellations on clay tablets, the earliest known star catalogues were compiled by the ancient Babylonians of Mesopotamia in the late 2nd millennium BC, during the Kassite Period.
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They are better known by their Assyrian-era name'Three Stars Each'; these star catalogues, written on clay tablets, listed thirty-six stars: twelve for "Anu" along the celestial equator , twelve for "Ea" south of that, twelve for " Enlil " to the north. The Mul. Apin lists, dated to sometime before the Neo-Babylonian Empire , are direct textual descendants of the "Three Stars Each" lists and their constellation patterns show similarities to those of Greek civilization.
In Ancient Greece , the astronomer and mathematician Eudoxus laid down a full set of the classical constellations around BC, his catalogue Phaenomena, rewritten by Aratus of Soli between and BC as a didactic poem, became one of the most consulted astronomical texts in antiquity and beyond. It contains descriptions of the positions of the stars, the shapes of the constellations and provided information on their relative times of rising and setting.
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Hipparchus completed his star catalogue in BC, which he compared to Timocharis' and discovered that the longitude of the stars had changed over time; this led him to determine the first value of the precession of the equinoxes. In the 2nd century, Ptolemy of Roman Egypt published a star catalogue as part of his Almagest , which listed 1, stars visible from Alexandria. Ptolemy's catalogue was based entirely on an earlier one by Hipparchus, it remained the standard star catalogue in the Arab worlds for over eight centuries. The Islamic astronomer al-Sufi updated it in , the star positions were redetermined by Ulugh Beg in , but it was not superseded until the appearance of the thousand-star catalogue of Tycho Brahe in Although the ancient Vedas of India specified how the ecliptic was to be divided into twenty-eight nakshatra , Indian constellation patterns were borrowed from Greek ones sometime after Alexander's conquests in Asia in the 4th century BC.
The earliest known inscriptions for Chinese star names were written on oracle bones and date to the Shang Dynasty. An earlier lacquerware chest found in the Tomb of Marquis Yi of Zeng contains a complete list of the names of the twenty-eight mansions. It was not until the Han Dynasty that astronomers started to observe and record names for all the stars that were apparent in the night sky, not just those around the ecliptic.
Sima's catalogue—the Book of Celestial Offices —includes some 90 constellations, the stars therein named after temples, ideas in philosophy, locations such as markets and shops, different people such as farmers and soldiers. For his Spiritual Constitution of the Universe of AD, the astronomer Zhang Heng compiled a star catalogue comprising constellations. Chinese constellation names were adopted by the Koreans and Japanese. A large number of star catalogues were published by Muslim astronomers in the medieval Islamic world; these were Zij treatises, including Arzachel's Tables of Toledo , the Maragheh observatory's Zij-i Ilkhani and Ulugh Beg's Zij-i-Sultani.
Apparent magnitude The apparent magnitude of an astronomical object is a number, a measure of its brightness as seen by an observer on Earth. The magnitude scale is logarithmic. The measurement of apparent magnitudes or brightnesses of celestial objects is known as photometry.
Apparent magnitudes are used to quantify the brightness of sources at ultraviolet and infrared wavelengths. An apparent magnitude is measured in a specific passband corresponding to some photometric system such as the UBV system. The brightest stars in the night sky were said to be of first magnitude, whereas the faintest were of sixth magnitude, the limit of human visual perception. Each grade of magnitude was considered twice the brightness of the following grade, although that ratio was subjective as no photodetectors existed; this rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest and is believed to have originated with Hipparchus.
In , Norman Robert Pogson formalized the system by defining a first magnitude star as a star, times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today; this implies that a star of magnitude m is about 2. This figure, the fifth root of , became known as Pogson's Ratio ; the zero point of Pogson's scale was defined by assigning Polaris a magnitude of 2. Astronomers discovered that Polaris is variable, so they switched to Vega as the standard reference star, assigning the brightness of Vega as the definition of zero magnitude at any specified wavelength.
Apart from small corrections, the brightness of Vega still serves as the definition of zero magnitude for visible and near infrared wavelengths, where its spectral energy distribution approximates that of a black body for a temperature of K. However, with the advent of infrared astronomy it was revealed that Vega's radiation includes an Infrared excess due to a circumstellar disk consisting of dust at warm temperatures.
At shorter wavelengths, there is negligible emission from dust at these temperatures. However, in order to properly extend the magnitude scale further into the infrared, this peculiarity of Vega should not affect the definition of the magnitude scale. Therefore, the magnitude scale was extrapolated to all wavelengths on the basis of the black-body radiation curve for an ideal stellar surface at K uncontaminated by circumstellar radiation.
On this basis the spectral irradiance for the zero magnitude point, as a function of wavelength, can be computed. Small deviations are specified between systems using measurement apparatuses developed independently so that data obtained by different astronomers can be properly compared, but of greater practical importance is the definition of magnitude not at a single wavelength but applying to the response of standard spectral filters used in photometry over various wavelength bands.
With the modern magnitude systems, brightness over a wide range is specified according to the logarithmic definition detailed below, using this zero reference. In practice such apparent magnitudes do not exceed 30; the brightness of Vega is exceeded by four stars in the night sky at visible wavelengths as well as the bright planets Venus and Jupiter , these must be described by negative magnitudes.
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Negative magnitudes for other bright astronomical objects can be found in the table below. Astronomers have developed other photometric zeropoint systems as alternatives to the Vega system; the most used is the AB magnitude system, in which photometric zeropoints are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference.
The AB magnitude zeropoint is defined such that an object's AB and Vega-based magnitudes will be equal in the V filter band. As the amount of light received by a telescope is reduced by transmission through the Earth's atmosphere, any measurement of apparent magnitude is corrected for what it would have been as seen from above the atmosphere. The dimmer an object appears, the higher the numerical value given to its apparent magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of From Wikipedia, the free encyclopedia.
November , "Validation of the new Hipparcos reduction", Astronomy and Astrophysics , 2 : —, arXiv : Part I. January , "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society , 1 : —, arXiv : Retrieved 18 June February , "Origins of the ancient constellations: I. Volume 3. New York: Dover Publication, Inc.see
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The origins of the earliest constellations likely go back to prehistory. Babylonian tablet recording Halley's Comet in BC. Ancient Egyptian star chart and decanal clock on the ceiling from the tomb of Senenmut.
Artist's impression of Aludra , a B5 supergiant seen in Canis Major. Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right.
A dense starfield in Sagittarius. A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. A star-forming region in the Large Magellanic Cloud. False-color imagery of the Sun , a G-type main-sequence star , the closest to Earth. The constellation of Leo as it can be seen by the naked eye. Lines have been added.
Andromeda as depicted in Urania's Mirror, set of constellation cards published in London c. The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving along the ecliptic red , which is tilted Wheel of the zodiac: This 6th century mosaic pavement in a synagogue incorporates Greek-Byzantine elements, Beit Alpha , Israel. The 1st century BC Dendera zodiac 19th-century engraving. Mediaeval stained glass by Andre Robin after the fire of The Sun is the star at the center of the Solar System.
It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 1. During a total solar eclipse , the solar corona can be seen with the naked eye, during the brief period of totality. Taken by Hinode 's Solar Optical Telescope on 12 January , this image of the Sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity.
Visible light photograph of sunspot, 13 December In this false-color ultraviolet image, the Sun shows a C3-class solar flare white area on upper left , a solar tsunami wave-like structure, upper right and multiple filaments of plasma following a magnetic field, rising from the stellar surface. Victoria is a state in south-eastern Australia. Victoria is Australia's smallest mainland state and its second-most populous state overall, thus making it the most densely populated state overall. The building was intended to be finished with a dome , but was not completed due to budget constraints.
The Legislative Council Chamber, as photographed in One of many local government seats, Geelong Town Hall. Its name is Latin for scorpion, and its symbol is. Scorpius is one of the 48 constellations identified by the Greek astronomer Ptolemy in the second century. It is an ancient constellation that pre-dated the Greeks. The constellation Scorpius as it can be seen by naked eye with constellation lines drawn in. Scorpius as depicted in Urania's Mirror , a set of constellation cards published in London c.
Stellar parallax is the apparent shift of position of any nearby star against the background of distant objects. Hubble precision stellar distance measurement has been extended 10 times further into the Milky Way.