Star of Barnard - SpeedyLook encyclopedia

The star of Barnard is a star of the constellation of Ophiuchus. This Naine red of standard M is mainly known to be the star having the own Mouvement most important (10,3" per annum). The star is named in the honor of the Astronome Edward Emerson Barnard which discovered this property in 1916. Located at a distance from 1,828 Parsec (that is to say 5,96 light-years), it is the fifth star nearest to the Ground after the Sun and the three components of Alpha Centauri. The star is however invisible with the naked eye because of its weak luminosity.

The star of Barnard was the subject of many work and is probably the dwarf M most studied because of its proximity and its position close to the celestial equator which is favorable to the observation. Research concentrated on the properties of star and detection possible planets extrasolaires. The star was thus the object of a scientific Controverse when Peter van of Kamp announced in 1963 to have detected disturbances in the own movement of star which seemed to indicate the presence of one or more Planet S joviennes. This discovery appeared finally erroneous. The star of Barnard was also a target star at the time of a study on the feasibility of an uninhabited fast voyage worms of the stellar systems close to the Solar system.

The star of Barnard in the history of astronomy

The star of Barnard was referred in the first Catalog of Munich and in the Albany General Catalogs under respective designations Munich 15040 (time 1850.0 then 1880.0) and AGC 6005 (time 1910.0). Van de Kamp had observed star since 1938 in order to detect with colleagues of the observatory of the Swarthmore College of thin variations of a micrometer of its position on photographic plates. These variations were supposed to correspond to orbital Perturbations of star indicating the presence of a planetary companion. Van de Kamp made measure the positions by groups going to ten people, then calculated the average of the results in order to avoid the systematic errors of measurement due to each individual. Van de Kamp put forth the assumption that the star of Barnard was accompanied by a planet of 1,6 mass jovienne to 4,4 UA on a slightly eccentric orbit, work refined in 1969. Later the same year, it suggested two planets from respectively 0,8 and 1,1 masses joviennes. This discovery was in general accepted in the scientific community during the the Sixties.

Other astronomers tried to reproduce work of Van de Kamp. Two important articles refuting the existence of one or more planets were published in 1973. Starting from photographs carried out in another observatory, Gatewood and Eichhorn did not manage to check the existence of a planetary companion in spite of novel methods of measurements on the plates. Another article published by Hershey four months later, using the Observatory of Swarthmore which had used Van de Kamp, suggested a possible cause with the variations observed. It noted that the changes of the astrometrical field several stars were related to the time adjustments and modifications carried out on the lenses of the Télescope: the movement observed was an artefact due to the maintenance and the update of the material of observation.

Van de Kamp refused all its life to recognize its error. Although being a very admired and sociable man, Van de Kamp would have felt betrayed by his/her colleagues who disputed his discoveries. Wulff Heintz, which succeeded Van de Kamp with Swarthmore and was expert of the double stars, questioned its discoveries and published criticisms of its work starting from 1976. The relations between the two men would then have distended. In 1982, Van de Kamp published a supposed new article to confirm the existence of two planets.

The research undertaken during the Years 1980 and 1990 in order to find companions planetary with star of Barnard proved to be unfruitful. The interferometric studies carried out using the Space telescope Hubble in 1999 did not identify either of planetary companion. All these failures do not make it possible however to completely exclude the existence from planets of low mass orbiting around star of Barnard. Although the controversy slowed down work on the planets extrasolaires, it contributed to the celebrity of star of Barnard.

Stellar system

The star of Barnard is a Naine red of standard M4. Its Magnitude connects is of 9,57 compared with -1,5 for Sirius (the most luminous star of the sky) and 6 for the least luminous objects visible with the naked eye; the scale being logarithmic curve, a star magnitude connects 9,57 is thus too much weak to be visible with the naked eye.

The star of Barnard would have been formed there is approximately 10 billion years. This old star thus lost most of its energy of rotation and the periodic changes of its luminosity indicate that its period of rotation is 130 days (against 25 for the Sun). Because of its age, it was supposed a long time that the star of Barnard did not have a significant stellar activity. However, of the astronomers observed in 1998 intense a solar eruption: the star of Barnard thus forms part of the eruptive stars. The star is also called V2500 Ophiuchi in the designation of variable stars. The own movement of star represents a transverse speed of 90 km/s. the 10,3 seconds of arc annually traversed correspond to a quarter of degree during an human life, that is to say about half of the angular diameter of Full moon. Its radial speed can be measured by Doppler effect. Two measurements are given in the catalogs of stars: 106,8 km/s in Simbad, and 110,8 km/s in ARICNS and the others. These measurements, combined with the own movement, suggest a real speed compared to the Sun of 139,7 and 142,7 km/s respectively In fact, the star of Barnard so quickly approaches Sun which it will be at 3,8 light-years of the solar system (against 5,96 currently) about the year: 11800. It will be then the star nearest to the Sun. Its temperature of surface east of 3134 (±102) K, its visual Luminosité is the 4/10 000e and its bolometric Luminosité of 34,6/10 000e of those of the Sun.]] The research tasks on star of Barnard were numerous. The main theme of study was the search for planets following work of Van de Kamp, but many other fields of study are documented.

Stellar characteristics and astrometry

Several articles on the relations mass-luminosity were published before the final work of Dawson in 2003. In addition to specifying the temperature and the luminosity, the article suggested that the preceding estimates of the ray of Star of Barnard underestimate his value; he proposes 0,20 solar Rayon (± 0,008 solar ray) which is located towards the maximum values typically considered.

The work carried out by Benedict and his/her colleagues starting from the Space telescope Hubble has a great range. In 1999, the absolute parallax and the absolute magnitude were specified. Gatewood thus could show in 1995 that there were no planets of 10 masses joviennes (lower limit for the brown dwarf ) around star of Barnard. The article of 1999 with Hubble made it possible to exclude the planetary companions from 0,8 masses joviennes of orbital period lower than 1000 days lower than 7,5 terrestrial masses and a mass lower than 3,1 masses of Neptune (quite lower than the smallest estimates of Van de Kamp). Being given the random nature of the eruptions, it indicated that " the star would be fantastic to observe for astronomers amateurs".

Daedalus project

See too

List of close stars

External bonds

Page of star of Barnard, '' solstation.com ''
Barnard' S Star and the Detection off Extrasolar Planets, '' weblore.com ''

Source

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