William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse, KP ( born June 17, 1800 York, † October 31, 1867 in Birr Castle) was an Irish astronomer. In heaven known union publications, his name is often abbreviated as Lord Rosse.
He was known in particular for his giant telescopes of metal mirrors, with which he could first explore the structure of spiral nebulae in the 1840s.
Life
Until the death of his father he took the courtesy title of Lord Oxmantown. After the usual private lessons in 1818, he studied first at the University of Dublin, went to Oxford in 1819 and studied at Magdalen College. 1821 Parsons was elected to the House of Commons ( until 1834 ). Already in 1824 he was elected to the Royal Astronomical Society. In 1831 he became Lord Lieutenant of King's County in 1834 and colonel of militia. In February 1845 he was elected a Representative Peer of Ireland. From 1848 to 1854 he was president of the Royal Society, in 1862 Chancellor of the University of Dublin. In 1836 he had married Mary Wilmer Field; they had four sons. William Parsons, 3rd Earl of Rosse, died on October 31, 1867 at his country estate Birr Castle.
The lunar crater Rosse is named after him.
Performance
Large reflecting telescopes
1826 taught Lord Rosse in his country house an observatory one, for which he had under his personal direction make the instruments. In 1828 he published his experiences during the grinding and polishing of the mirror in the Edinburgh Journal of Science. After 1839, a telescope of 36 inches ( 91 cm) manufactured diameter ( in construction very similar to the famous telescopes of William Herschel ), he observed star clusters and the mysterious fog like M27 or M31. He said to find clues on pile of stars within the diffuse luminous gas masses. (Incidentally, he gave the " Crab Nebula " (M 1) his nickname. ) To the resolving power to further increase and thus to clarify the true nature of the misty objects that he built at a cost of £ 12,000 a giant telescope, which in 1845 completed. The primary mirror measure 72 inches (1.83 m ) in diameter and had a focal length of 16 m. This telescope was characterized by one for that time incredibly high light intensity, and soon got the nickname "Leviathan of Parsonstown ". Lord Rosse had to develop together with its employees various techniques themselves, to make this device a reality.
Nebulae and galaxies
Parsons worked in particular on nebulae and recognized in his large telescopes as many distant star clusters. But he could see the spiral nebulae because of their low surface brightness is not as distant " island universes " indicate how the present-day galaxies began to call around 1900. Because they are difficult to visually observe the resolution astrophotography of the 20th century was reserved in details only. However, he sensed in several of these fog spiral structures (a total of 14 ), which met with doubt long. First he saw the spiral arms in 1845 at the relatively nearby " Whirlpool Galaxy " (M51 in the Messier catalog) - just a few weeks after start of his giant telescope (see his drawing). On the nearby, but very faint Triangulum Galaxy ( M33 ), he konne make four spiral arms.
Since Lord Rosse - unlike Herschel - did not believe in an evolving universe, he was looking for evidence that the foggy spots, from which should evolve according to Herschel stars, actually were made of countless tiny suns. In this sense, he claimed that he had been able to resolve individual stars in the Orion Nebula, which led Herschel to angry attacks. However, the Orion Nebula is a emission nebula is a real gas clouds, the light of galaxies comes from billions of stars to this conclusion, his son Laurence already had come after it with the 36 - inch telescope 11: ( The question could only be clarified later by spectral analysis. fog spectra was visually examined. )
The idea of the fog were made of stars, was not an invention of Lord Rosse. Already John Herschel had speculated M51 was a brother ( "brother system" ) of the Milky Way and had - as William Henry Smyth - theorize that they were gigantic systems of countless stars. Lord Rosse was hoping to be able to resolve with his giant telescope nebulae such as M51 (which in 1917 succeeded the Andromeda Nebula ). Instead, he recognized the M51, a spiral structure and thus fueled the debate about the true nature of these systems even more. For the representatives of the nebular theory held the scrolls to the outcome huge vortex in gas masses. Few astronomers voted to horses - as Stephan Alexander, who wrote in 1851: The Milky Way and the stars in her form a spiral and several ( maybe 4 ) arms and a central star cluster [ GDRoth, History of Astronomy p.102 ].
The nebulae were not the only work area in which Lord Rosse worked. Considerable energy he spent on the investigation of the temperature of the lunar surface.
His numerous research results were presented under the title Observations of Nebulae and Clusters of Stars made with the 6- foot and 3 -foot Reflectors at Birr Castle.
Alternative design for Newtonian telescope
Parsons invented (similar to Herschel ) an alternative to the lateral eye of the Newtonian telescope, because its mirror it were large enough. These writes Meyers encyclopedia 1885: The ' giant telescopes ' of Herschel and Lord Rosse, whose levels were 1-2 m in diameter, such a secondary mirror, and thus the induced light from him loss was avoided by a simple trick. The concave mirror (SS, Fig 5) that is a little inclined to the axis of the tube so that the small picture is to lie close to the edge of the mirror and can be viewed through an eyepiece lens there. It certainly occurs, the head of the observer in part before the opening of the tube, but this is at the large diameter of the mirror of little consequence.
Lord Rosse was also charity work, trying to alleviate the suffering in his country, see his writing Letters on the state of Ireland ( London 1847).