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The Galactic Center is the rotational center of the Milky Way. The estimates for its location range from 7.6 to 8.7 kiloparsecs (about 25 000 to 28 000 lightyears) from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest. There is strong evidence consistent with the existence of a supermassive black hole at the Galactic Center of the Milky Way. == Proof of existence and location == Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths. The available information about the Galactic Center comes from observations at gamma ray, hard X-ray, infrared, sub-millimetre and radio wavelengths. Harlow Shapley stated in 1918 that the halo of globular clusters surrounding the Milky Way seemed to be centered on the star swarms in the constellation of Sagittarius, but the dark molecular clouds in the area blocked the view for optical astronomers. In the early 1940s Walter Baade at Mount Wilson Observatory took advantage of wartime blackout conditions in nearby Los Angeles to conduct a search for the center with the 100 inch Hooker Telescope. He found near the star Alnasl (Gamma Sagittarii) a one-degree-wide void in the interstellar dust lanes, giving a relatively clear view through the spiral arms of our Galaxy to the swarms of stars around the nucleus. This gap has been known as Baade's Window ever since. He was not satisfied that he had pinpointed the galactic center, and when the Mount Palomar telescopes were commissioned around 1950, he applied them to the task also, with no success. At Dover Heights in Sydney, Australia a team of radio astronomers from the Division of Radiophysics at the CSIRO, led by Joseph Lade Pawsey, used a 'sea interferometer' to discover some of the first interstellar and intergalactic radio sources, including Taurus A, Virgo A and Centaurus A. By 1954 they had built an 80 feet (24.4 meters) fixed dish antenna and used it to make a detailed study of an extended, extremely powerful belt of radio emission that was detected in Sagittarius. They named an intense point-source near the center of this belt Sagittarius A, and realised that it was located at the very center of our Galaxy, despite being some 32 degrees south-west of the conjectured galactic center of the time. In 1958 the International Astronomical Union (IAU) decided to adopt the position of Sagittarius A as the true zero co-ordinate point for the system of galactic latitude and longitude. In the equatorial coordinate system the location is: RA 17h45m40.04s, Dec −29° 00' 28.1" (J2000 epoch). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Galactic Center」の詳細全文を読む スポンサード リンク
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