A star catalogue or star catalog, is an astronomical catalogue that lists stars. 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. 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 370 BC, his catalogue Phaenomena, rewritten by Aratus of Soli between 275 and 250 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. In the 3rd century BC, the Greek astronomers Timocharis of Alexandria and Aristillus created another star catalogue. Hipparchus completed his star catalogue in 129 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 1,022 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 964, the star positions were redetermined by Ulugh Beg in 1437, but it was not superseded until the appearance of the thousand-star catalogue of Tycho Brahe in 1598.
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. Sources dating from the Zhou Dynasty which provide star names include the Zuo Zhuan, the Shi Jing, the "Canon of Yao" in the Book of Documents; the Lüshi Chunqiu written by the Qin statesman Lü Buwei provides most of the names for the twenty-eight mansions. 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. Star catalogues are traditionally attributed to Shi Shen and Gan De, two rather obscure Chinese astronomers who may have been active in the 4th century BC of the Warring States period; the Shi Shen astronomy is attributed to Shi Shen, the Astronomic star observation to Gan De.
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. A star catalogue is featured in one of the chapters of the late 2nd-century-BC history work Records of the Grand Historian by Sima Qian and contains the "schools" of Shi Shen and Gan De's work. 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 120 AD, the astronomer Zhang Heng compiled a star catalogue comprising 124 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.
Rings of Uranus
The rings of Uranus are a system of rings around the planet Uranus, intermediate in complexity between the more extensive set around Saturn and the simpler systems around Jupiter and Neptune. The rings of Uranus were discovered on March 10, 1977, by James L. Elliot, Edward W. Dunham, Jessica Mink. William Herschel had reported observing rings in 1789. By 1978, nine distinct rings were identified. Two additional rings were discovered in 1986 in images taken by the Voyager 2 spacecraft, two outer rings were found in 2003–2005 in Hubble Space Telescope photos. In the order of increasing distance from the planet the 13 known rings are designated 1986U2R/ζ, 6, 5, 4, α, β, η, γ, δ, λ, ε, ν and μ, their radii range from about 38,000 km for the 1986U2R/ζ ring to about 98,000 km for the μ ring. Additional faint dust bands and incomplete arcs may exist between the main rings; the rings are dark—the Bond albedo of the rings' particles does not exceed 2%. They are composed of water ice with the addition of some dark radiation-processed organics.
The majority of Uranus's rings are only a few kilometers wide. The ring system contains little dust overall; some rings are optically thin: the broad and faint 1986U2R/ζ, μ and ν rings are made of small dust particles, while the narrow and faint λ ring contains larger bodies. The relative lack of dust in the ring system may be due to aerodynamic drag from the extended Uranian exosphere; the rings of Uranus are thought to be young, not more than 600 million years old. The Uranian ring system originated from the collisional fragmentation of several moons that once existed around the planet. After colliding, the moons broke up into many particles, which survived as narrow and optically dense rings only in confined zones of maximum stability; the mechanism that confines the narrow rings is not well understood. It was assumed that every narrow ring had a pair of nearby shepherd moons corralling them into shape. In 1986 Voyager 2 discovered only one such shepherd pair around the brightest ring; the first mention of a Uranian ring system comes from William Herschel's notes detailing his observations of Uranus in the 18th century, which include the following passage: "February 22, 1789: A ring was suspected".
Herschel drew a small diagram of the ring and noted that it was "a little inclined to the red". The Keck Telescope in Hawaii has since confirmed this to be the case, at least for the ν ring. Herschel's notes were published in a Royal Society journal in 1797. In the two centuries between 1797 and 1977 the rings are mentioned, if at all; this casts serious doubt on whether Herschel could have seen anything of the sort while hundreds of other astronomers saw nothing. It has been claimed that Herschel gave accurate descriptions of the ε ring's size relative to Uranus, its changes as Uranus travelled around the Sun, its color; the definitive discovery of the Uranian rings was made by astronomers James L. Elliot, Edward W. Dunham, Jessica Mink on March 10, 1977, using the Kuiper Airborne Observatory, was serendipitous, they planned to use the occultation of the star SAO 158687 by Uranus to study the planet's atmosphere. When their observations were analyzed, they found that the star disappeared from view five times both before and after it was eclipsed by the planet.
They deduced. The five occultation events they observed were denoted by the Greek letters α, β, γ, δ and ε in their papers; these designations have been used as the rings' names since then. They found four additional rings: one between the β and γ rings and three inside the α ring; the former was named the η ring. The latter were dubbed rings 4, 5 and 6—according to the numbering of the occultation events in one paper. Uranus's ring system was the second to be discovered after that of Saturn; the rings were directly imaged when the Voyager 2 spacecraft flew through the Uranian system in 1986. Two more faint rings were revealed; the Hubble Space Telescope detected an additional pair of unseen rings in 2003–2005, bringing the total number known to 13. The discovery of these outer rings doubled the known radius of the ring system. Hubble imaged two small satellites for the first time, one of which, shares its orbit with the outermost newly discovered μ ring; as understood, the ring system of Uranus comprises thirteen distinct rings.
In order of increasing distance from the planet they are: 1986U2R/ζ, 6, 5, 4, α, β, η, γ, δ, λ, ε, ν, μ rings. They can be divided into three groups: two dusty rings and two outer rings; the rings of Uranus consist of macroscopic particles and little dust, although dust is known to be present in 1986U2R/ζ, η, δ, λ, ν and μ rings. In addition to these well-known rings, there may be numerous optically thin dust bands and faint rings between them; these faint rings and dust bands may exist only temporarily or consist of a number of separate arcs, which are sometimes detected during occultations. Some of them became visible during a series of ring plane-crossing events in 2007. A number of dust bands between the rings were observed in forward-scattering geometry by Voyager 2. All rings of Uranus show azimuthal brightness variations; the rings are made of an dark material. The geometric albedo of the ring particles does not exceed 5–6%, while the Bond albedo is lower—about 2%; the rings particles demonstrate a steep opposition surge—an increase of the albe
In astronomy, declination is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the celestial equator, along the hour circle passing through the point in question; the root of the word declination means "a bending away" or "a bending down". It comes from the same root as the words recline. In some 18th and 19th century astronomical texts, declination is given as North Pole Distance, equivalent to 90 -. For instance an object marked as declination -5 would have a NPD of 95, a declination of -90 would have a NPD of 180. Declination in astronomy is comparable to geographic latitude, projected onto the celestial sphere, hour angle is comparable to longitude. Points north of the celestial equator have positive declinations, while those south have negative declinations. Any units of angular measure can be used for declination, but it is customarily measured in the degrees and seconds of sexagesimal measure, with 90° equivalent to a quarter circle.
Declinations with magnitudes greater than 90° do not occur, because the poles are the northernmost and southernmost points of the celestial sphere. An object at the celestial equator has a declination of 0° north celestial pole has a declination of +90° south celestial pole has a declination of −90°The sign is customarily included whether positive or negative; the Earth's axis rotates westward about the poles of the ecliptic, completing one circuit in about 26,000 years. This effect, known as precession, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, equatorial coordinates are inherently relative to the year of their observation, astronomers specify them with reference to a particular year, known as an epoch. Coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch; the used standard epoch is J2000.0, January 1, 2000 at 12:00 TT. The prefix "J" indicates. Prior to J2000.0, astronomers used the successive Besselian Epochs B1875.0, B1900.0, B1950.0.
A star's direction remains nearly fixed due to its vast distance, but its right ascension and declination do change due to precession of the equinoxes and proper motion, cyclically due to annual parallax. The declinations of Solar System objects change rapidly compared to those of stars, due to orbital motion and close proximity; as seen from locations in the Earth's Northern Hemisphere, celestial objects with declinations greater than 90° − φ appear to circle daily around the celestial pole without dipping below the horizon, are therefore called circumpolar stars. This occurs in the Southern Hemisphere for objects with declinations less than −90° − φ. An extreme example is the pole star which has a declination near to +90°, so is circumpolar as seen from anywhere in the Northern Hemisphere except close to the equator. Circumpolar stars never dip below the horizon. Conversely, there are other stars that never rise above the horizon, as seen from any given point on the Earth's surface. If a star whose declination is δ is circumpolar for some observer a star whose declination is −δ never rises above the horizon, as seen by the same observer.
If a star is circumpolar for an observer at latitude φ it never rises above the horizon as seen by an observer at latitude −φ. Neglecting atmospheric refraction, declination is always 0 ° at west points of the horizon. At the north point, it is 90° − |φ|, at the south point, −90° + |φ|. From the poles, declination is uniform around the entire horizon 0°. Non-circumpolar stars are visible only during certain seasons of the year; the Sun's declination varies with the seasons. As seen from arctic or antarctic latitudes, the Sun is circumpolar near the local summer solstice, leading to the phenomenon of it being above the horizon at midnight, called midnight sun. Near the local winter solstice, the Sun remains below the horizon all day, called polar night; when an object is directly overhead its declination is always within 0.01 degrees of the observer's latitude. The first complication applies to all celestial objects: the object's declination equals the observer's astronomic latitude, but the term "latitude" ordinarily means geodetic latitude, the latitude on maps and GPS devices.
In the continental United States and surrounding area, the difference is a few arcseconds but can be as great as 41 arcseconds. The second complication is that, assuming no deflection of the vertical, "overhead" means perpendicular to the ellipsoid at observer's location, but the perpendicular line does not pass through the center of the earth. For the moon this discrepancy can reach 0.003 degrees.
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The term is used in astronomy, but can refer to any situation in which an object in the foreground blocks from view an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft when foreground objects obscure distant objects dynamically, as the scene changes over time; the term occultation is most used to describe those frequent occasions when the Moon passes in front of a star during the course of its orbital motion around the Earth. Since the Moon, with an angular speed with respect to the stars of 0.55 arcsec/s or 2.7 µrad/s, has a thin atmosphere and stars have an angular diameter of at most 0.057 arcseconds or 0.28 µrad, a star, occulted by the Moon will disappear or reappear in 0.1 seconds or less on the Moon's edge, or limb. Events that take place on the Moon's dark limb are of particular interest to observers, because the lack of glare allows these occultations to more be observed and timed.
The Moon's orbit is inclined to the ecliptic, any stars with an ecliptic latitude of less than about 6.5 degrees may be occulted by it. There are three first magnitude stars that are sufficiently close to the ecliptic that they may be occulted by the Moon and by planets – Regulus and Antares. Occultations of Aldebaran are presently only possible by the Moon, because the planets pass Aldebaran to the north. Neither planetary nor lunar occultations of Pollux are possible. However, in the far future, occultations of Pollux will be possible; some deep-sky objects, such as the Pleiades, can be occulted by the Moon. Within a few kilometres of the edge of an occultation's predicted path, referred to as its northern or southern limit, an observer may see the star intermittently disappearing and reappearing as the irregular limb of the Moon moves past the star, creating what is known as a grazing lunar occultation. From an observational and scientific standpoint, these "grazes" are the most dynamic and interesting of lunar occultations.
The accurate timing of lunar occultations is performed by astronomers. Lunar occultations timed to an accuracy of a few tenths of a second have various scientific uses in refining our knowledge of lunar topography. Photoelectric analysis of lunar occultations have discovered some stars to be close visual or spectroscopic binaries; some angular diameters of stars have been measured by timing of lunar occultations, useful for determining effective temperatures of those stars. Early radio astronomers found occultations of radio sources by the Moon valuable for determining their exact positions, because the long wavelength of radio waves limited the resolution available through direct observation; this was crucial for the unambiguous identification of the radio source 3C 273 with the optical quasar and its jet, a fundamental prerequisite for Maarten Schmidt's discovery of the cosmological nature of quasars. Several times during the year, someone on Earth can observe the Moon occulting a planet. Since planets, unlike stars, have significant angular sizes, lunar occultations of planets will create a narrow zone on Earth from which a partial occultation of the planet will occur.
An observer located within that narrow zone could observe the planet's disk blocked by the moving moon. The same mechanic can be seen with the Sun, where observers on Earth will view it as a solar eclipse. Therefore, a total solar eclipse is the same event as the Moon occulting the Sun. Stars may be occulted by planets. Occultations of bright stars are rare. In 1959, Venus occulted Regulus, the next occultation of a bright star will be in 2044. Uranus's rings were first discovered when that planet occulted a star in 1977. On 3 July 1989, Saturn passed in front of the 5th magnitude star 28 Sagittarii. Pluto occulted stars in 1988, 2002, 2006, allowing its tenuous atmosphere to be studied via atmospheric limb sounding. In rare cases, one planet can pass in front of another. If the nearer planet appears larger than the more distant one, the event is called a mutual planetary occultation. An occultation occurs; these occultations are useful for measuring the size and position of minor planets much more than can be done by any other means.
A cross-sectional profile of the shape of an asteroid can be determined if a number of observers at different, locations observe the occultation. Occultations have been used to estimate the diameter of trans-Neptunian objects such as 2002 TX300, Varuna. In addition, mutual occultation and eclipsing events can occur between a minor planet and its satellite. A large number of these minor-planet moons have been discovered analyzing the photometric light curves of rotating minor planets and detecting a second, superimposed brightness variation, from which an orbital period for the satellite, a secondary-to-primary diameter-ratio can be derived. On 29 May 1983, 2 Pallas occulted the naked-eye bright spectroscopic binary star 1 Vulpeculae along a track across the southern United States, northern Mexico, north parts of the Caribbean. Observations from 130 different locations defined the shape of about two-thirds of the asteroid, detected the secondary companion of the bright binary star.
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. A difference of 1 in magnitude corresponds to a change in brightness by a factor of 5√100, or about 2.512. The brighter an object appears, the lower its magnitude value, with the brightest astronomical objects having negative apparent magnitudes: for example Sirius at −1.46. 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. In standard astronomical notation, an apparent magnitude in the V filter band would be denoted either as mV or simply as V, as in "mV = 15" or "V = 15" to describe a 15th-magnitude object; the scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes.
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 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star, 100 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 2.512 times as bright as a star of magnitude m + 1. This figure, the fifth root of 100, 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 11000 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 11000 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. For example, the brightest star of the celestial sphere, has an apparent magnitude of −1.4 in the visible. 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 100. Therefore, the apparent magnitude m, in the spectral band x, would be given by m x = − 5 log 100 , more expressed in terms of common logarithms as m x
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus' atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water and methane, along with traces of other hydrocarbons, it is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K, has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is composed of ices and rock. Like the other giant planets, Uranus has a ring system, a magnetosphere, numerous moons; the Uranian system has a unique configuration because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit.
Its north and south poles, lie where most other planets have their equators. In 1986, images from Voyager 2 showed Uranus as an featureless planet in visible light, without the cloud bands or storms associated with the other giant planets. Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second. Uranus is the only planet whose name is derived directly from a figure from Greek mythology, from the Latinised version of the Greek god of the sky Ouranos. Like the classical planets, Uranus is visible to the naked eye, but it was never recognised as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel announced its discovery on 13 March 1781, expanding the known boundaries of the Solar System for the first time in history and making Uranus the first planet discovered with a telescope. Uranus had been observed on many occasions before its recognition as a planet, but it was mistaken for a star.
The earliest known observation was by Hipparchos, who in 128 BC might have recorded it as a star for his star catalogue, incorporated into Ptolemy's Almagest. The earliest definite sighting was in 1690, when John Flamsteed observed it at least six times, cataloguing it as 34 Tauri; the French astronomer Pierre Charles Le Monnier observed Uranus at least twelve times between 1750 and 1769, including on four consecutive nights. Sir William Herschel observed Uranus on 13 March 1781 from the garden of his house at 19 New King Street in Bath, Somerset and reported it as a comet. Herschel "engaged in a series of observations on the parallax of the fixed stars", using a telescope of his own design. Herschel recorded in his journal: "In the quartile near ζ Tauri... either Nebulous star or a comet." On 17 March he noted: "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place." When he presented his discovery to the Royal Society, he continued to assert that he had found a comet, but implicitly compared it to a planet: The power I had on when I first saw the comet was 227.
From experience I know that the diameters of the fixed stars are not proportionally magnified with higher powers, as planets are. Moreover, the comet being magnified much beyond what its light would admit of, appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain; the sequel has shown that my surmises were well-founded, this proving to be the Comet we have observed. Herschel notified the Astronomer Royal Nevil Maskelyne of his discovery and received this flummoxed reply from him on 23 April 1781: "I don't know what to call it, it is as to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a eccentric ellipsis. I have not yet seen any coma or tail to it."Although Herschel continued to describe his new object as a comet, other astronomers had begun to suspect otherwise. Finnish-Swedish astronomer Anders Johan Lexell, working in Russia, was the first to compute the orbit of the new object.
Its nearly circular orbit led him to a conclusion. Berlin astronomer Johann Elert Bode described Herschel's discovery as "a moving star that can be deemed a hitherto unknown planet-like object circulating beyond the orbit of Saturn". Bode concluded; the object was soon universally accepted as a new planet. By 1783, Herschel acknowledged this to Royal Society president Joseph Banks: "By the observation of the most eminent Astronomers in Europe it appears that the new star, which I had the honour of pointing out to them in March 1781, is a Primary Planet of our Solar System." In recognition of his achievement, King George III gave Herschel an annual stipend of £200 on condition that he move to Windsor so that the Royal Family could look through his telescopes. The name of Uranus references the ancient Greek deity of the sky Uranus, the father of Cronus and grandfather of Zeus, wh
Smithsonian Astrophysical Observatory
The Smithsonian Astrophysical Observatory is a research institute of the Smithsonian Institution headquartered in Cambridge, where it is joined with the Harvard College Observatory to form the Harvard–Smithsonian Center for Astrophysics. The SAO was founded in 1890 by Samuel Pierpont Langley, the Smithsonian's third Secretary for studies of the sun. Langley is remembered today as an aeronautical pioneer, but he was trained as an astronomer and was the first American scientist to perceive "astrophysics" as a distinct field. Langley discovered infrared radiation from the sun. In 1955, the SAO moved from Washington, D. C. to Cambridge, to affiliate with HCO and to expand its staff and most its scientific scope. Fred Whipple, the first director of SAO in this new era, accepted a national challenge to create a worldwide satellite-tracking network, a decision that would establish SAO as a pioneer and leader in space science research. Smithsonian and the USAF Project Space Track shared observations and ephemerides throughout the early days of satellite tracking, 1957–1961.
In 1973, the ties between Smithsonian and Harvard were strengthened and formalized by the creation of the joint Harvard-Smithsonian CfA. SAO has operated a number of remote stations over the years. More than 300 scientists at the CfA are engaged in a broad program of research in astronomy, astrophysics and space sciences, science education. SAO's pioneering efforts in the development of orbiting observatories and large ground-based telescopes, the application of computers to astrophysical problems, the integration of laboratory measurements, theoretical astrophysics, observations across the electromagnetic spectrum have contributed much to our current understanding of the universe; the Chandra X-ray Observatory is operated by SAO from Cambridge. With the University of Arizona, SAO manages the MMT Observatory. Samuel Pierpont Langley 1890–1906 Charles Greeley Abbot 1906–1942 Loyal Blaine Aldrich 1942–1955 Fred Lawrence Whipple 1955–1973 George B. Field 1973–1982 Irwin I. Shapiro 1982–2004 Charles R. Alcock 2004– SAO homepage Harvard-Smithsonian Center for Astrophysics