Observatory of the Wilson Mount

The observatory of the mount Wilson ( Mount Wilson Observatory , MWO ) is a astronomical Observatoire located in the Comté of Los Angeles, in California. It is at the top of the mount Wilson, with 1.742 Mètre S of altitude, in the chain of the mounts San Gabriel close to Pasadena, in the North-East of Los Angeles.

Weak atmospheric turbulences and the quality of the air at the top of the Wilson mount quite naturally do of it one of the best sites for the astronomical observation of North America, and in particular for the Interférométrie. The growth of the agglomeration of Los Angeles however reduced the possibilities for the observatory of scanning the objects of the deep sky, but the site remains all the same an important place for the scientific research.

History

The solar observatory of the mount Wilson was founded in 1904 by George Ellery Hale, under the patronage of the foundation Carnegie Institution off Washington , itself founded two years before. Fifteen years earlier, in 1889, the observatory of Harvard via William Henry Pickering had also built to him an observatory at the top of the Wilson mount, but the very hard winter 1889-1890 returned the living conditions of the very difficult astronomers, and the site was deserted after only 18 months.

Instruments

The telescope Hauls of 1,5 meter

George Ellery Hale accepted the mirror of 1,5 meter (60 inches) in 1896, in gift on behalf of her father, William Hale. This mirror, manufactured in France by Saint-Gobain, measurement 191 mm thickness and weighs 860 kg. Haul having received the required funds with the establishment of the observatory only in 1904, the assembly of the Télescope started in 1905 and lasted two years. The mounting and the structure of the telescope were built with San Francisco, and were likely to resist the Earthquake of 1906. The telescope was brought into service for the first time on December 8th 1908, it acted at the time of the largest telescope in service in the world.

The Hale telescope quickly became one of the astronomical most prolific and crowned instruments success in the Histoire of astronomy of the 20th century. It made it possible to make important advances in the fields of the Spectrométrie, measurements of Parallaxe and photography S of Nébuleuse S. Although exceeded cuts some by the Hooker telescope nine years after its startup, the Hale telescope remained during several decades one of the largest operational telescopes.

In 1992 it was equipped with a system of adaptive Optique ( Atmospheric Compensation Experiment , ACE). This system improved considerably the To be able of resolution of the instrument while passing of 0,5-1 Seconde of arc to 0,07 second of arc.

Currently the Hale telescope is not any more used for the scientific research and is put at the service of the public, the instruments placed at its hearth having been replaced by Oculaire S. it probably acts of the largest telescope freely accessible to the general public throughout the world.

The George Hauls Solar Telescope belonged to the National Historic Landmark. Another telescope, located at the Mount Palomar (and measuring more than 5 meters in diameter), bears the name of Hale Telescope .

The Hooker telescope of 2,5 meters

At once after the startup of the first telescope, Hale decided to create an instrument even larger. The funds came, in addition to the Carnegie foundation, of John D. Hooker, from where the name of the telescope. Once again the mirror was produced by Saint-Gobain, between 1906 and 1908, and after some vexations during the phase of construction, the telescope, of a diameter of 2,5 meters, finally was brought into service on November 1st 1917.

The relatively complex mechanism of the instrument included a float with mercury which allowed to flux the movements of the apparatus. In 1919 the Hooker telescope was equipped with a new instrument, a optical Interféromètre developed by the Nobel Prize of physics Albert Abraham Michelson. It was the first time that such an instrument was used in astronomy, and it made it possible Michelson more precisely to measure dimensions and the distance from certain stars, such as for example Bételgeuse. Henry Norris Russell developed his system of classification of stars on the basis of observation carried out using the Hooker .

Edwin Hubble, as, used to him the observations made on the Hooker to arrive at the conclusion as part of the Nébuleuse S observed until there were actually Galaxie S located well beyond our clean Milky Way.

The Hooker telescope remained during very a long time the largest telescope of the world, until the telescope Hale of 5 meters of the Palomar mount was completed in 1949.

This telescope was put at the retirement in 1986, then given in state after being equipped with adaptive Optique in 1992. Its To be able of resolution is from now on of 0,05 second of arc.

Solar telescopes

The site has three solar telescopes, of which two are still used by the scientists. The construction of the solar tower of 18 meters was completed in 1908, and that of the tower of 46 meters in 1912. The solar telescope Snow, moved since the site of the Observatoire Yerkes in 1904 from now on is used only for educational demonstrations.

Interferometers

Very weak turbulences in the air above the Wilson Mount make of it a place privileged for the use of the Interférométrie. Michelson carried out the first direct measurements of apparent star diameter (others that the Sun) on the Hooker in 1919.

The infra-red space Interferometer ( Space Infrared Interferometer , ISI) is a whole of three telescopes of 1,7 meter diameter and working in the close relation Infrarouge. The maximum distance between the various telescopes is of 70 meters. This instrument is controlled by the the University of California. The maximum base line (70 m) makes it possible to reach a resolution of 0,003 Seconde of arc to 11 Micromètre S.

The Center for High Angular Resolution Astronomy (CHARA) is an interferometer made up of six telescopes of 1 meter each one and placed on three different axes which can reach a maximum separation of 330 meters. This instrument is directed by the Université of Georgia, and took up duty in 2002. In the infra-red, the maximum angular resolution obtained is of 0,0005 second of arc.

Discovered

This nonexhaustive chronology lists some of discovered most outstanding realized at the observatory of the Wilson Mount:

December 13rd 1920: the first measurement of the apparent diameter of a star (Bételgeuse, by Francis Pease and Albert Abraham Michelson by interferometry using the telescope Hooker ;
October 5th 1923: Edwin Hubble discovers a variable céphéide in the Galaxie of Andromède;
March 15th 1929: helped of observations carried out at the observatory, Hubble publishes the law connecting the distance from the galaxies at their speed of recession, thus confirming the thesis of the Expansion of the universe;
August 24th 1937: Olin Wilson discovers the first star Wolf-Rayet;
June 6th 1938: Seth Barnes Nicholson discovers to it tenth the moon of Jupiter (Lysithéa) (he will discover in all four of the Jupiter satellites, including three with the Wilson Mount);
June 18th 1941: Walter Baade discovers the Rémanent supernova of SN 1604, the supernova of Kepler ;

See too

List of the largest telescopes
List of the astronomical observatories

External bonds

Official site

the telescope Hauls
the telescope Hooker
Webcam located at the top of the solar telescope of 46m

interferometer CHARA

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