History
Mizar, in Ursa Major, was observed to be double by Giovanni Battista Riccioli in 1650 (and probably earlier by Benedetto Castelli and Galileo). The identification of other doubles soon followed: Robert Hooke discovered one of the first double-star systems, Gamma Arietis, in 1664, while the bright southern star Acrux, in the Southern Cross, was discovered to be double by Fontenay in 1685. Since that time, the search has been carried out thoroughly and the entire sky has been examined for double stars down to a limiting apparent magnitude of about 9.0. At least 1 in 18 stars brighter than 9.0 magnitude in the northern half of the sky are known to be double stars visible with a 36-inch (910 mm) telescope.
The unrelated categories of optical doubles and true binaries are lumped together for historical and practical reasons. When Mizar was found to be a binary, it was quite difficult to determine whether a double star was a binary system or only an optical double. Improved telescopes, spectroscopy, and photography are the basic tools used to make the distinction. After it was determined to be a visual binary, Mizar's components were found to be spectroscopic binaries themselves. Additionally, Mizar forms an optical double with the star Alcor. With a separation of 3 lightyears, it is doubted, but not absolutely proven, that there is no significant gravitational interaction between them. Thus "double star" remains a useful term for pairs whose status is not fully known.
Read more about this topic: Double Star
Famous quotes containing the word history:
“The History of the world is not the theatre of happiness. Periods of happiness are blank pages in it, for they are periods of harmony—periods when the antithesis is in abeyance.”
—Georg Wilhelm Friedrich Hegel (1770–1831)
“No one is ahead of his time, it is only that the particular variety of creating his time is the one that his contemporaries who are also creating their own time refuse to accept.... For a very long time everybody refuses and then almost without a pause almost everybody accepts. In the history of the refused in the arts and literature the rapidity of the change is always startling.”
—Gertrude Stein (1874–1946)
“In the history of the United States, there is no continuity at all. You can cut through it anywhere and nothing on this side of the cut has anything to do with anything on the other side.”
—Henry Brooks Adams (1838–1918)