A variable star is a star whose brightness as seen from Earth fluctuates. This variation may be caused by a change in emitted light or by something blocking the light, so variable stars are classified as either: Intrinsic variables, whose luminosity changes. Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth. Many most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle. An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. Of the modern astronomers, the first variable star was identified in 1638 when Johannes Holwarda noticed that Omicron Ceti pulsated in a cycle taking 11 months; this discovery, combined with supernovae observed in 1572 and 1604, proved that the starry sky was not eternally invariable as Aristotle and other ancient philosophers had taught.
In this way, the discovery of variable stars contributed to the astronomical revolution of the sixteenth and early seventeenth centuries. The second variable star to be described was the eclipsing variable Algol, by Geminiano Montanari in 1669. Chi Cygni was identified in 1686 by G. Kirch R Hydrae in 1704 by G. D. Maraldi. By 1786 ten variable stars were known. John Goodricke himself discovered Beta Lyrae. Since 1850 the number of known variable stars has increased especially after 1890 when it became possible to identify variable stars by means of photography; the latest edition of the General Catalogue of Variable Stars lists more than 46,000 variable stars in the Milky Way, as well as 10,000 in other galaxies, over 10,000'suspected' variables. The most common kinds of variability involve changes in brightness, but other types of variability occur, in particular changes in the spectrum. By combining light curve data with observed spectral changes, astronomers are able to explain why a particular star is variable.
Variable stars are analysed using photometry, spectrophotometry and spectroscopy. Measurements of their changes in brightness can be plotted to produce light curves. For regular variables, the period of variation and its amplitude can be well established. Peak brightnesses in the light curve are known as maxima. Amateur astronomers can do useful scientific study of variable stars by visually comparing the star with other stars within the same telescopic field of view of which the magnitudes are known and constant. By estimating the variable's magnitude and noting the time of observation a visual lightcurve can be constructed; the American Association of Variable Star Observers collects such observations from participants around the world and shares the data with the scientific community. From the light curve the following data are derived: are the brightness variations periodical, irregular, or unique? What is the period of the brightness fluctuations? What is the shape of the light curve? From the spectrum the following data are derived: what kind of star is it: what is its temperature, its luminosity class? is it a single star, or a binary? does the spectrum change with time?
Changes in brightness may depend on the part of the spectrum, observed if the wavelengths of spectral lines are shifted this points to movements strong magnetic fields on the star betray themselves in the spectrum abnormal emission or absorption lines may be indication of a hot stellar atmosphere, or gas clouds surrounding the star. In few cases it is possible to make pictures of a stellar disk; these may show darker spots on its surface. Combining light curves with spectral data gives a clue as to the changes that occur in a variable star. For example, evidence for a pulsating star is found in its shifting spectrum because its surface periodically moves toward and away from us, with the same frequency as its changing brightness. About two-thirds of all variable stars appear to be pulsating. In the 1930s astronomer Arthur Stanley Eddington showed that the mathematical equations that describe the interior of a star may lead to instabilities that cause a star to pulsate; the most common type of instability is related to oscillations in the degree of ionization in outer, convective layers of the star.
Suppose the star is in the swelling phase. Its outer layers expand; because of the decreasing temperature the degree of ionization decreases. This makes the gas more transparent, thus makes it easier for the star to radiate its energy; this in turn will make the star start to contract. As the gas is thereby compressed, it is heated and the degree of ionization again increases. Thi
John Flamsteed FRS was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, Catalogus Britannicus, a star atlas called Atlas Coelestis, both published posthumously, he made the first recorded observations of Uranus, although he mistakenly catalogued it as a star, he laid the foundation stone for the Royal Greenwich Observatory. Flamsteed was born in Denby, England, the only son of Stephen Flamsteed and his first wife, Mary Spadman, he was educated at the free school of Derby and at Derby School, in St Peter's Churchyard, near where his father carried on a malting business. At that time, most masters of the school were Puritans. Flamsteed had a solid knowledge of Latin, essential for reading the scientific literature of the day, a love of history, leaving the school in May, 1662, his progress to Jesus College, recommended by the Master of Derby School, was delayed by some years of chronic ill health. During those years, Flamsteed gave his father some help in his business, from his father learnt arithmetic and the use of fractions, developing a keen interest in mathematics and astronomy.
In July 1662, he was fascinated by the thirteenth-century work of Johannes de Sacrobosco, De sphaera mundi, on 12 September 1662 observed his first partial solar eclipse. Early in 1663, he read Thomas Fale's Horologiographia: The Art of Dialling, which set off an interest in sundials. In the summer of 1663, he read Wingate's Canon, William Oughtred's Canon, Thomas Stirrup's Art of Dialling. At about the same time, he acquired Thomas Street's Astronomia Carolina, or A New Theory of the Celestial Motions, he associated himself with local gentlemen interested in astronomy, including William Litchford, whose library included the work of the astrologer John Gadbury which included astronomical tables by Jeremiah Horrocks, who had died in 1641 at the age of twenty-two. Flamsteed was impressed by the work of Horrocks. In August 1665, at the age of nineteen and as a gift for his friend Litchford, Flamsteed wrote his first paper on astronomy, entitled Mathematical Essays, concerning the design and construction of an astronomer's quadrant, including tables for the latitude of Derby.
In September 1670, Flamsteed visited Cambridge and entered his name as an undergraduate at Jesus College. While it seems he never took up full residence, he was there for two months in 1674, had the opportunity to hear Isaac Newton's Lucasian Lectures. Ordained a deacon, he was preparing to take up a living in Derbyshire when he was invited to London by his patron Jonas Moore, Surveyor-General of the Ordnance. Moore had made an offer to the Royal Society to pay for the establishment of an observatory; these plans were, preempted when Charles II was persuaded by his mistress, Louise de Kérouaille, Duchess of Portsmouth, to hear about a proposal to find longitude by the position of the Moon from an individual known as Le Sieur de St Pierre. Charles appointed a Royal Commission to examine the proposal in December 1674, consisting of Lord Brouncker, Seth Ward, Samuel Moreland, Christopher Wren, Silius Titus, John Pell and Robert Hooke. Having arrived in London on 2 February 1675, staying with Jonas Moore at the Tower of London, Flamsteed had the opportunity to be taken by Titus to meet the King.
He was subsequently admitted as an official Assistant to the Royal Commission and supplied observations in order to test St Pierre's proposal and to offer his own comments. The Commission's conclusions were that, although St Pierre's proposal was not worth further consideration, the King should consider establishing an observatory and appointing an observer in order to better map the stars and the motions of the Moon in order to underpin the successful development of the lunar-distance method of finding longitude. On 4 March 1675 Flamsteed was appointed by royal warrant "The King's Astronomical Observator" — the first English Astronomer Royal, with an allowance of £100 a year; the warrant stated his task as "rectifieing the Tables of the motions of the Heavens, the places of the fixed stars, so as to find out the so much desired Longitude of places for Perfecteing the Art of Navigation". In June 1675, another royal warrant provided for the founding of the Royal Greenwich Observatory, Flamsteed laid the foundation stone on 10 August.
In February 1676, he was admitted a Fellow of the Royal Society, in July, he moved into the Observatory where he lived until 1684, when he was "levated to the priesthood appointed rector" of the small village of Burstow, near Crawley in Surrey. He held that office, as well as that of Astronomer Royal, until his death, he is buried at Burstow, the east window in the church was dedicated to him as a memorial. The will of Flamsteed’s widow, left instructions for her own remains to be deposited “in the same Grave in which Mr John Flamsteed is buryed in the Chancell of Burstow Church.” She left instructions, twenty five pounds, for the executor of her will to place “in the aforesaid Chancell of Burstow… A Marble stone or Monument, with an inscription in Latin, in memory of the late Reverend Mr. John Flamsteed.” It seems no such monument was created, 200 years a plaque was placed to mark his burial in the chancel. After his death, his papers and scientific instruments were taken by his widow; the papers were returned many years but the instruments disappeared.
Flamsteed calculated the solar eclipses of 1666 and 1668. He was responsible for several of the earliest recorded sightings of the planet Uranus, which he mistook for a star and catalogued as'34 Tauri'; the first of these was in December 1690, which re
A binary star is a star system consisting of two stars orbiting around their common barycenter. Systems of two or more stars are called multiple star systems; these systems when more distant appear to the unaided eye as a single point of light, are revealed as multiple by other means. Research over the last two centuries suggests that half or more of visible stars are part of multiple star systems; the term double star is used synonymously with binary star. Optical doubles are so called because the two stars appear close together in the sky as seen from the Earth, their "doubleness" depends only on this optical effect. A double star can be revealed as optical by means of differences in their parallax measurements, proper motions, or radial velocities. Most known double stars have not been studied adequately to determine whether they are optical doubles or doubles physically bound through gravitation into a multiple star system. Binary star systems are important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated.
This determines an empirical mass-luminosity relationship from which the masses of single stars can be estimated. Binary stars are detected optically, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known, they may be detected by indirect techniques, such as spectroscopy or astrometry. If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, these close binary systems can exchange mass, which may bring their evolution to stages that single stars cannot attain. Examples of binaries are Sirius, Cygnus X-1. Binary stars are common as the nuclei of many planetary nebulae, are the progenitors of both novae and type Ia supernovae; the term binary was first used in this context by Sir William Herschel in 1802, when he wrote: If, on the contrary, two stars should be situated near each other, at the same time so far insulated as not to be materially affected by the attractions of neighbouring stars, they will compose a separate system, remain united by the bond of their own mutual gravitation towards each other.
This should be called a real double star. By the modern definition, the term binary star is restricted to pairs of stars which revolve around a common center of mass. Binary stars which can be resolved with a telescope or interferometric methods are known as visual binaries. For most of the known visual binary stars one whole revolution has not been observed yet, they are observed to have travelled along a curved path or a partial arc; the more general term double star is used for pairs of stars which are seen to be close together in the sky. This distinction is made in languages other than English. Double stars may be binary systems or may be two stars that appear to be close together in the sky but have vastly different true distances from the Sun; the latter are termed optical optical pairs. Since the invention of the telescope, many pairs of double stars have been found. Early examples include Acrux. Mizar, in the Big Dipper, was observed to be double by Giovanni Battista Riccioli in 1650; the bright southern star Acrux, in the Southern Cross, was discovered to be double by Father Fontenay in 1685.
John Michell was the first to suggest that double stars might be physically attached to each other when he argued in 1767 that the probability that a double star was due to a chance alignment was small. William Herschel began observing double stars in 1779 and soon thereafter published catalogs of about 700 double stars. By 1803, he had observed changes in the relative positions in a number of double stars over the course of 25 years, concluded that they must be binary systems. Since this time, many more double stars have been measured; the Washington Double Star Catalog, a database of visual double stars compiled by the United States Naval Observatory, contains over 100,000 pairs of double stars, including optical doubles as well as binary stars. Orbits are known for only a few thousand of these double stars, most have not been ascertained to be either true binaries or optical double stars; this can be determined by observing the relative motion of the pairs. If the motion is part of an orbit, or if the stars have similar radial velocities and the difference in their proper motions is small compared to their common proper motion, the pair is physical.
One of the tasks that remains for visual observers of double stars is to obtain sufficient observations to prove or disprove gravitational connection. Binary stars are classified into four types accordi
Mira variables, named for the prototype star Mira, are a class of pulsating variable stars characterized by red colours, pulsation periods longer than 100 days, amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths. They are red giants in the late stages of stellar evolution, on the asymptotic giant branch, that will expel their outer envelopes as planetary nebulae and become white dwarfs within a few million years. Mira variables are stars massive enough that they have undergone helium fusion in their cores but are less than two solar masses, stars that have lost about half their initial mass. However, they can be thousands of times more luminous than the Sun due to their large distended envelopes, they are pulsating due to the entire star contracting. This produces a change in temperature along with radius, both of which factors cause the variation in luminosity; the pulsation depends on the mass and radius of the star and there is a well-defined relationship between period and luminosity.
The large visual amplitudes are not due to large luminosity changes, but due to a shifting of energy output between infra-red and visual wavelengths as the stars change temperature during their pulsations. Early models of Mira stars assumed. A recent survey of Mira variable stars found that 75% of the Mira stars which could be resolved using the IOTA telescope are not spherically symmetric, a result, consistent with previous images of individual Mira stars, so there is now pressure to do realistic three-dimensional modelling of Mira stars on supercomputers. Mira variables may be carbon-rich. Carbon-rich stars such as R Leporis arise from a narrow set of conditions that override the normal tendency for AGB stars to maintain a surplus of oxygen over carbon at their surfaces due to dredge-ups. Pulsating AGB stars such as Mira variables undergo fusion in alternating hydrogen and helium shells, which produces periodic deep convection known as dredge-ups; these dredge-ups bring carbon from the helium burning shell to the surface and would result in a carbon star.
However, in stars above about 4 M☉, hot bottom burning occurs. This is when the lower regions of the convective region are hot enough for significant CN cycle fusion to take place which destroys much of the carbon before it can be transported to the surface, thus more massive AGB stars do not become carbon-rich. Mira variables are losing mass and this material forms dust shrouds around the star. In some cases conditions are suitable for the formation of natural masers. A small subset of Mira variables appear to change their period over time: the period increases or decreases by a substantial amount over the course of several decades to a few centuries; this is believed to be caused by thermal pulses, where the helium shell reignites the outer hydrogen shell. This changes the structure of the star; this process is predicted to happen to all Mira variables, but the short duration of thermal pulses over the asymptotic giant branch lifetime of the star, means we only see it in a few of the several thousand Mira stars known in R Hydrae.
Most Mira variables do exhibit slight cycle-to-cycle changes in period caused by nonlinear behaviour in the stellar envelope including deviations from spherical symmetry. Mira variables are popular targets for amateur astronomers interested in variable star observations, because of their dramatic changes in brightness; some Mira variables have reliable observations stretching back well over a century. The following list contains selected Mira variables. Unless otherwise noted, the given magnitudes are in the V-band. Long period variable Semiregular variable star
Hipparcos was a scientific satellite of the European Space Agency, launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky; this permitted the accurate determination of proper motions and parallaxes of stars, allowing a determination of their distance and tangential velocity. When combined with radial velocity measurements from spectroscopy, this pinpointed all six quantities needed to determine the motion of stars; the resulting Hipparcos Catalogue, a high-precision catalogue of more than 118,200 stars, was published in 1997. The lower-precision Tycho Catalogue of more than a million stars was published at the same time, while the enhanced Tycho-2 Catalogue of 2.5 million stars was published in 2000. Hipparcos' follow-up mission, was launched in 2013; the word "Hipparcos" is an acronym for HIgh Precision PARallax COllecting Satellite and a reference to the ancient Greek astronomer Hipparchus of Nicaea, noted for applications of trigonometry to astronomy and his discovery of the precession of the equinoxes.
By the second half of the 20th century, the accurate measurement of star positions from the ground was running into insurmountable barriers to improvements in accuracy for large-angle measurements and systematic terms. Problems were dominated by the effects of the Earth's atmosphere, but were compounded by complex optical terms and gravitational instrument flexures, the absence of all-sky visibility. A formal proposal to make these exacting observations from space was first put forward in 1967. Although proposed to the French space agency CNES, it was considered too complex and expensive for a single national programme, its acceptance within the European Space Agency's scientific programme, in 1980, was the result of a lengthy process of study and lobbying. The underlying scientific motivation was to determine the physical properties of the stars through the measurement of their distances and space motions, thus to place theoretical studies of stellar structure and evolution, studies of galactic structure and kinematics, on a more secure empirical basis.
Observationally, the objective was to provide the positions and annual proper motions for some 100,000 stars with an unprecedented accuracy of 0.002 arcseconds, a target in practice surpassed by a factor of two. The name of the space telescope, "Hipparcos" was an acronym for High Precision Parallax Collecting Satellite, it reflected the name of the ancient Greek astronomer Hipparchus, considered the founder of trigonometry and the discoverer of the precession of the equinoxes; the spacecraft carried a single all-reflective, eccentric Schmidt telescope, with an aperture of 29 cm. A special beam-combining mirror superimposed two fields of view, 58 degrees apart, into the common focal plane; this complex mirror consisted of two mirrors tilted in opposite directions, each occupying half of the rectangular entrance pupil, providing an unvignetted field of view of about 1°×1°. The telescope used a system of grids, at the focal surface, composed of 2688 alternate opaque and transparent bands, with a period of 1.208 arc-sec.
Behind this grid system, an image dissector tube with a sensitive field of view of about 38-arc-sec diameter converted the modulated light into a sequence of photon counts from which the phase of the entire pulse train from a star could be derived. The apparent angle between two stars in the combined fields of view, modulo the grid period, was obtained from the phase difference of the two star pulse trains. Targeting the observation of some 100,000 stars, with an astrometric accuracy of about 0.002 arc-sec, the final Hipparcos Catalogue comprised nearly 120,000 stars with a median accuracy of better than 0.001 arc-sec. An additional photomultiplier system viewed a beam splitter in the optical path and was used as a star mapper, its purpose was to monitor and determine the satellite attitude, in the process, to gather photometric and astrometric data of all stars down to about 11th magnitude. These measurements were made in two broad bands corresponding to B and V in the UBV photometric system.
The positions of these latter stars were to be determined to a precision of 0.03 arc-sec, a factor of 25 less than the main mission stars. Targeting the observation of around 400,000 stars, the resulting Tycho Catalogue comprised just over 1 million stars, with a subsequent analysis extending this to the Tycho-2 Catalogue of about 2.5 million stars. The attitude of the spacecraft about its center of gravity was controlled to scan the celestial sphere in a regular precessional motion maintaining a constant inclination between the spin axis and the direction to the Sun; the spacecraft spun around its Z-axis at the rate of 11.25 revolutions/day at an angle of 43° to the Sun. The Z-axis rotated about the sun-satellite line at 6.4 revolutions/year. The spacecraft consisted of two platforms and six vertical panels, all made of aluminum honeycomb; the solar array consisted of three deployable sections. Two S-band antennas were located on the top and bottom of the spacecraft, providing an omni-directional downlink data rate of 24 kbit/s.
An attitude and orbit-control subsystem ensured correct dynamic attitude control and determination during the operational lifetim
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
Johann Elert Bode
Johann Elert Bode was a German astronomer known for his reformulation and popularisation of the Titius–Bode law. Bode suggested the planet's name. Bode was born in Hamburg; as a youth, he suffered from a serious eye disease which damaged his right eye. His early promise in mathematics brought him to the attention of Johann Georg Büsch, who allowed Bode to use his own library for study, he began his career with the publication of a short work on the solar eclipse of 5 August 1766. This was followed by an elementary treatise on astronomy entitled Anleitung zur Kenntniss des gestirnten Himmels, the success of which led to his being invited to Berlin by Johann Heinrich Lambert in 1772 for the purpose of computing ephemerides on an improved plan. There he founded, in 1774, the well-known Astronomisches Jahrbuch, 51 yearly volumes of which he compiled and issued, he became director of the Berlin Observatory in 1786, from which he retired in 1825. There he published the Uranographia in 1801, a celestial atlas that aimed both at scientific accuracy in showing the positions of stars and other astronomical objects, as well as the artistic interpretation of the stellar constellation figures.
The Uranographia marks the climax of an epoch of artistic representation of the constellations. Atlases showed fewer and fewer elaborate figures until they were no longer printed on such tables. Bode published another small star atlas, intended for astronomical amateurs, he is credited with the discovery of Bode's Galaxy. Comet Bode is named after him. Asteroid 998 Bodea, discovered on 6 August 1923 by Karl Reinmuth at Heidelberg, was christened in his honour, the letter'a' added to its name to fulfil the convention that asteroids were given feminine names, his name became attached to the'law' discovered by Johann Daniel Titius in 1766. Bode first makes mention of it in the Anleitung zur Kenntniss des gestirnten Himmels in a footnote, although it is officially called the Titius–Bode law, it is commonly just called Bode's law; this law attempts to explain the distances of the planets from the Sun in a formula although it breaks down for the planet Neptune, discovered in Berlin. It was the discovery of Uranus at a position predicted by the law which aroused great interest in it.
There was a gap between Mars and Jupiter, Bode urged a search for a planet in this region which culminated in a group formed for this purpose, the so-called "Celestial Police". However before the group initiated a search, they were trumped by the discovery of the asteroid Ceres by Giuseppe Piazzi from Palermo in 1801, at Bode's predicted position. Latterly, the law fell out of favour when it was realised that Ceres was only one of a small number of asteroids and when Neptune was found not to be in a position required by the law; the discovery of planets around other stars has brought the law back into discussion. Bode himself was directly involved in research leading from the discovery of a planet – that of Uranus in 1781. Although Uranus was the first planet to be discovered by telescope, it is just about visible with the naked eye. Bode consulted older star charts and found numerous examples of the planet's position being given while being mistaken for a star, for example John Flamsteed, Astronomer Royal in Britain, had listed it in his catalogue of 1690 as a star with the name 34 Tauri.
These earlier sightings allowed an exact calculation of the orbit of the new planet. Bode was responsible for giving the new planet its name; the discoverer William Herschel proposed to name it after George III, not accepted so in other countries. Bode opted for Uranus, with the apparent logic that just as Saturn was the father of Jupiter, the new planet should be named after the father of Saturn. There were further alternatives proposed, but Bode's suggestion became the most used – however it had to wait until 1850 before gaining official acceptance in Britain when the Nautical Almanac Office switched from using the name Georgium Sidus to Uranus. In 1789, Bode's Royal Academy colleague Martin Klaproth was inspired by Bode's name for the planet to name his newly discovered element "uranium". From 1787 to 1825 Bode was director of the Astronomisches Rechen-Institut. In 1794, he was elected a foreign member of the Royal Swedish Academy of Sciences. In April 1789 he was elected a fellow of the Royal Society.
Bode died in Berlin on 23 November 1826, aged 79. 1768 Anleitung zur Kentniss des Gestirnten Himmels 1774-1957 Berliner Astronomisches Jahrbuch für 1776–1959 1776 Sammlung astronomischer Tafeln 1776 Erläuterung der Sternkunde, an introductory book on the constellations and their tales, reprinted more than ten times 1782 Vorstellung der Gestirne... des Flamsteadschen Himmelsatlas Verzeichniss 1801 Uranographia sive Astrorum Descriptio Allgemeine Beschreibung und Nachweisung der Gestirne His works were effective in diffusing throughout Germany a taste for astronomy. Schwemin, Friedhelm. Der Berliner Astr