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| Alternative names | Observatoire de Paris | ||
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| Location | Montparnasse,14th arrondissement of Paris,Paris,Grand Paris, France | ||
| Coordinates | 48°48′18″N2°14′00″E / 48.8051°N 2.23337°E /48.8051; 2.23337 | ||
| Established | 1667 (1667) | ||
| Website | www | ||
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  Location of Paris Observatory - PSL | |||
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TheParis Observatory (French:Observatoire de Paris,pronounced[ɔbsɛʁvatwaʁdəpaʁi]), a research institution of theParis Sciences et Lettres University, is the foremostastronomical observatory ofFrance, and one of the largest astronomical centres in the world. Its historic building is on theLeft Bank of theSeine in centralParis, but most of the staff work on a satellite campus inMeudon, a suburb southwest of Paris.
The Paris Observatory was founded in 1667 as the first public observatory.[1][2] Construction was completed by the early 1670s and coincided with a major push for increased science, and the founding of theRoyal Academy of Sciences.[3] King Louis XIV's minister of finance organized a "scientific powerhouse" to increase understanding of astronomy, maritime navigation, and science in general.[3]
Through the centuries the Paris Observatory has continued in support of astronomical activities, and in the 21st century connects multiple sites and organizations, supporting astronomy and science, past and present.[4][5]
Administratively, it is agrand établissement of the FrenchMinistry of National Education, with a status close to that of a public university. Its missions include:[6]
It maintains a solar observatory atMeudon and a radio astronomy observatory atNançay.[6] It was also the home to theInternational Time Bureau until its dissolution in 1987.[7] It remains the source of legal time in France,[8] using multipleatomic fountain clocks maintained by itsSYRTE (Sytèmes de Référence Temps Espace) department.[9] The Paris Observatory Library, which was founded in 1785, provides the researchers with documentation and preserves the ancient books, archives, and heritage collections of the institution. Many collections are available online.[citation needed]
The Paris Observatory was proposed in 1665–1666 by theFrench Academy of Sciences, which had recently been founded by the Minister of FinanceJean-Baptiste Colbert. In 1666, KingLouis XIV authorized the building of the Observatory. OnMidsummer's Day 1667, members of the Academy of Sciences traced the future building's outline on a plot outside town near thePort Royal abbey, with theParis meridian exactly bisecting the site north–south.[10] The meridian line was used as a basis for navigation and would be used by French cartographers as theirprime meridian for more than 200 years.[citation needed]
The Paris Observatory predates by a few years theRoyal Greenwich Observatory in England, which was founded in 1675. The English philosopherJohn Locke visited the Paris Observatory on 28 August 1677, which he recorded in his journal: "At the Observatory we saw the Moon in a twenty-two foot glass, and Jupiter, with his satellites, in the same. The most remote was on the east, and the other three on the west. We also saw Saturn and his ring, in a twelve-foot glass, and one of his satellites. Monsieur Cassini told me, that the declination of the needle at Paris is about two and a half degrees to the west."[11]
Thearchitect of the Paris Observatory wasClaude Perrault whose brother,Charles, was secretary to Jean-Baptiste Colbert and superintendent of public works.[12] Optical instruments were supplied byGiuseppe Campani. Construction of the Observatory was completed in 1671, though the buildings were extended in 1730, 1810, 1834, 1850, and 1951.[13] The last extension incorporates the Meridian Room designed byJean Prouvé.[14]
In 1671 Saturn's moonIapetus was discovered from the observatory, followed byRhea in 1672.[15] The moonsDione andTethys were also discovered from the observatory in 1684.[15] In 1676 the staff concluded that light itself was travelling at a finite speed.[16]
The world's first national almanac, theConnaissance des temps, was published by the Observatory in 1679, using eclipses inJupiter's satellites to aid sea-farers in establishinglongitude. In 1863, the observatory published the first modernweather maps. In 1882, a 33 cm (13 in)astrographiclens was constructed, an instrument that catalysed what proved to be the over-ambitious internationalCarte du Ciel project.[citation needed]
In November 1913, the observatory used theEiffel Tower as anantenna, exchanged sustained radio signals with theUnited States Naval Observatory inWashington, D.C. to determine the exact difference of longitude between the two institutions.[17]
The Paris Observatory library preserves a great number of original works and letters of the Observatory and well known astronomers. The entire collection has been inventoried in an online archive called Calames.[18] Some of the work is now digitized on thedigital library such as those ofJohannes Hevelius,Jérôme Lalande andJoseph-Nicolas Delisle.
The title of Director of the Observatory was officially given for the first time toCésar-François Cassini de Thury by a Royal brevet dated November 12, 1771.[19] However, the important role played by his grandfather and father in this institution during its first century actually gave them somewhat the role of Director.[citation needed]
The observatory did not have a recognised Director until 1771, before that each member could do as they pleased.[20] SometimesGiovanni Cassini (1671–1712) andJacques Cassini (1712–1756) are listed as "Directors" retrospectively. The same goes for François Arago, who also was not actually a Director although he did have ade facto position of leadership and is often credited as such.[citation needed]
The current President of the Observatory isFabienne Casoli.[21]
The first site was the Paris headquarters established in 1667 by King Louis XIV of France. This facility had various work done on it over the centuries, and in 1927 the Meudon Observatory was added, which included a new site and facilities. It was built in 1891.[citation needed]
In addition to these sites, theMarseilles Observatory became a branch of the Paris Observatory in 1863.[22] In 1873, Marseilles Observatory detached from Paris Observatory.[23]
King Louis XIV purchased the land for his new observatory in March 1667.[24] This provided a site for the activities of the Academy of Sciences near to the city of Paris.[24] The original buildings was designed by Claude Perrault.[25] A dome and terrace was added in 1847.[25]
The Meudon site was constructed in the late 19th century byJules Janssen, one of the discoverers ofhelium. With a million francs and permission to build on the ruins of the old royal palace, he constructed one of the grandest observatories of its day, with a focus on astronomy and solar physics. After World War I, the observatory was integrated with the nearby Paris Observatory and became an important campus for that observatory. Even into the 21st century solar observations are conducted at the Meudon site, and the preserved Great Refractor (Grande lunette) and astronomical gardens overlooking the city of Paris have delighted visitors for decades. The site includes:
After the Second World War, French astronomers began designing and building instruments for radio astronomy.[27] A field station was established in 1953, and by the late 1950s several radio instruments were established.[27]In 1965 theNançay radio telescope was established, a design equivalent to an almost 100-metre dish.[28]
Also known as the Observatoire du Pic de Château Renard, theObservatoire de Saint-Véran was built in 1974 on top of the Pic de Château Renard (2,900 m or 9,500 ft), in the commune ofSaint-Véran in the Haut Queyras (Hautes Alpesdépartement). Acoronograph was in operation there for ten years; the dome was moved there from the Perrault building of the Observatoire de Paris.[citation needed]
Nowadays, the AstroQueyras amateur astronomy association operates the facility, using a 60 cm (24 in) telescope on loan from theObservatoire de Haute Provence. Numerousasteroids have been discovered there.[29]
Early telescopes were supplied by the famed craftsman Giuseppe Campani.[30] Cassini, an astronomer who worked in the early days of the Observatory, had used Campani's telescopes in the 1660s, and continued to do so when he moved to the Paris Observatory.[31]
The Marly tower, moved to the observatory in 1685 for mounting telescopes, was demolished in 1705.[32] The Marly tower was originally made for theVersailles water supply system (seeMachine de Marly), but was moved to the southern gardens area near the Paris Observatory.[33] The tower could hold theobjective lens for extremely long focal length aerial telescopes.[33]
In 1732 a quadrant instrument made by Langlois was established at the Observatory.[34]
In 1804 a telescope of 8.4 cm aperture, made by Bellet, was established on the roof of the observatory.[35] In 1807 aShort reflector telescope was acquired, and there were several instruments available including a 9 cm apertureDollond telescope, and a telescope by Lerebours.[35]
One of the special telescopes in the collection of the observatory, was the Passy telescope of KingLouis XV.[35] This telescope was built by Dom Noel in the late 18th century, and was a reflecting telescope with a 61 cm aperture bronze mirror.[35] In 1805 the mirror was re-polished, but it was tarnished again within two years; it remained at the Observatory until it was dismantled in 1841.[36]
A Lerebours telescope of 24.4 cm aperture was installed in 1823, at a cost of 14,500 francs.[37] In 1835 Arago used this telescope to observe the return ofHalley's Comet that year.[37]
In 1837 the Gambeymural circle was installed, and also a transit instrument, also by Gambey.[38]
In 1857 arefracting telescope of 38 centimetres (14.96 in) apertureobjective, theArago equatorial telescope, was completed. This telescope was proposed by director François Arago in 1846.[25] It was installed in the east tower and was made by Lerebours.[38] This instrument is known to have conducted photometry measurements of Jupiter's moons (there were only four known at that time) in the late 1880s.[38]
In 1863 a largetransit circle was installed, and in 1878 a meridian instrument.[39] The transit circle of 1863 was made by Secretan and Eichens.[38]
In 1875 a 120 cm aperture silver-on-glass reflecting telescope was built, for 400,000 francs.[40]
This 120 cm diameter aperture telescope was a silvered glass mirror polished by Martin.[41] However, when it was mounted it was realized the gravity altered its shape because of the mirror's weight, thus causing an image quality issue.[41]
In 1886 a Henry astrograph with 13-inch objective was acquired.[38]
For the 1907Transit of Mercury, some of the telescopes used at the Paris Observatory included:[36]
The telescopes were mobile and were placed on the terrace for the observations.[36]
The Meudongreat refractor (Meudon 83-cm) is an 83 cm (33 in) aperture refractor, which, with September 20, 1909 observations byE. M. Antoniadi, helped disprove theMars canals theory. It is a double telescope completed in 1891, with a secondary 62 cm (24 in) aperture lens for photography. It was of the largest refracting telescopes in Europe and was active for a century until 1991. In the 21st century, it was renovated and supports public education and visitation.[citation needed]
The Meudon refractor was built atMeudon Observatory. It is one of three sites of the Paris Observatory; Meudon Observatory became part of the Paris Observatory in 1926.[42] The Meudon Great refractor is the third largest astronomical refractor of its type in the world.[43] The Meudon refractor is located in theGrande Coupole building, which was renovated in the early 2000s.[42]
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