Distinction from other nebulae

Distinction from other nebulae - Toward the end of the 18th...

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Distinction from other nebulae Sketch of Messier 51 by Lord Rosse in 1845, later known as the Whirlpool Galaxy In the 10th century, the Persian astronomer , Abd al-Rahman al-Sufi (known in the West as Azophi ), made the earliest recorded observation of the Andromeda Galaxy , describing it as a "small cloud". [30] Al-Sufi also identified the Large Magellanic Cloud , which is visible from Yemen , though not from Isfahan ; it was not seen by Europeans until Magellan 's voyage in the 16th century. [31] [32] These were the first galaxies other than the Milky Way to be observed from Earth. Al-Sufi published his findings in his Book of Fixed Stars in 964. In 1750 Thomas Wright , in his An original theory or new hypothesis of the Universe , speculated (correctly) that Milky Way was a flattened disk of stars, and that some of the nebulae visible in the night sky might be separate Milky Ways. [27] [33] In 1755 Immanuel Kant introduced the term "island universe" for these distant nebulae.
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Unformatted text preview: Toward the end of the 18th century, Charles Messier compiled a catalog containing the 109 brightest nebulae (celestial objects with a nebulous appearance), later followed by a larger catalog of 5,000 nebulae assembled by William Herschel. [27] In 1845, Lord Rosse constructed a new telescope and was able to distinguish between elliptical and spiral nebulae. He also managed to make out individual point sources in some of these nebulae, lending credence to Kant's earlier conjecture. [34] In 1912, Vesto Slipher made spectrographic studies of the brightest spiral nebulae to determine if they were made from chemicals that would be expected in a planetary system. However, Slipher discovered that the spiral nebulae had high red shifts, indicating that they were moving away at rate higher than the Milky Way's escape velocity . Thus they were not gravitationally bound to the Milky Way, and were unlikely to be a part of the galaxy....
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