William Parsons, 3rd Earl of Rosse

William Parsons, 3rd Earl of Rosse , KP (born June 17, 1800 in York , † October 31, 1867 in Birr Castle ) was an Irish astronomer . In celestial publications his name is often abbreviated as Lord Rosse .

He was best known for his giant telescopes made of metal mirrors, with which he was able to research the structure of spiral nebulae for the first time in the 1840s .

Life

Until his father's death, he carried the courtesy title of Lord Oxmantown . After the usual private tuition, he studied at Dublin University in 1818 , then went to Oxford in 1819 , where he studied at Magdalen College . In 1821 Parsons was elected to the House of Commons (until 1834). In 1824 he was accepted into the Royal Astronomical Society. In 1831 he became Lord Lieutenant of King's County and in 1834 Colonel of the Militia . In February 1845 he was elected Representative Peer of Ireland to the British House of Lords .

From 1848 to 1854 he was President of the Royal Society , from 1862 Chancellor of the University of Dublin. In 1845 he was elected an Honorary Fellow of the Royal Society of Edinburgh . In 1852 he became an honorary member of the Russian Academy of Sciences in St. Petersburg .

In 1836 he had married Mary Wilmer-Field; they had four sons. William Parsons, 3rd Earl of Rosse, died on October 31, 1867 in his country estate, Birr Castle.

The moon crater Rosse is named after him.

power

Large mirror telescopes

Giant telescope from Lord Rosse, Birr Castle, Co. Offaly

In 1826 Lord Rosse set up an observatory on his country estate , for which he had the instruments made under his personal direction. In 1828 he published his experience in grinding and polishing the mirror in the Edinburgh Journal of Science . After making a 36 inch (91 cm) diameter reflector telescope in 1839 ( very similar in design to the famous telescopes by William Herschel ), he observed star clusters and the mysterious nebulae like M27 or M31 . He thought he could find clues to clusters of stars within the diffuse glowing gas masses. (Incidentally, he gave the " Crab Nebula " [M 1] his nickname.) To further increase the resolution and thus clarify the true nature of the foggy objects, he built a giant telescope that was completed in 1845 at a cost of 12,000 pounds sterling . The primary mirror was 72 inches (1.83 m) in diameter and had a focal length of 16 m. This telescope was characterized by an unbelievably high light intensity for its time and soon got the nickname " Leviathan of Parsonstown ". Lord Rosse and his colleagues had to develop various techniques himself to make this device a reality.

Nebulae and galaxies

Drawing of the M 51 by Lord Rosse

Parsons worked in particular on nebulae and recognized many as distant star clusters in his large telescopes . However, because of their low surface brightness , he could not yet interpret the spiral nebulae as distant "islands of the world", as today's galaxies began to be called around 1900. Because they are difficult to observe visually, the resolution in details was only reserved for astrophotography in the 20th century. However, he suspected spiral structures in several of these nebulae (14 in total), which long met with doubts. First he saw the spiral arms in 1845 on the relatively close " Whirlpool Galaxy " (M51 in the Messier catalog ) - just a few weeks after his giant telescope was put into operation (see his drawing). He could also make out 4 spiral arms at the nearby, but very faint triangular nebula (M33).

Since Lord Rosse - unlike his adversary John Herschel - did not believe in an evolving universe, he looked for evidence that the misty spots from which Herschel said stars should develop actually consisted of innumerable small suns. With this in mind, he claimed that he had been able to break up the Orion Nebula into individual stars, which caused Herschel to make furious attacks. (The question could only be clarified later by means of spectral analysis : the Orion Nebula is a real gas nebula as an emission nebula, but the light of the galaxies comes from billions of stars. His son Laurence had already come to this conclusion after he had studied 11 Visually examined nebula spectra.)

The idea that nebulae are made of stars was not an invention of Lord Rosse. Already John Herschel had speculated M51 is a brother ( brother system ) of the Milky Way and had - as William Henry Smyth - theorized they were gigantic systems of countless stars. Lord Rosse had the hope of being able to resolve nebulae like M51 with his giant telescope (which was only possible in 1917 on the Andromeda Nebula ). Instead, he recognized a spiral structure in M51 and thus fueled the discussion about the true nature of these systems. Because the proponents of the fog theory considered the spirals to be the result of huge eddies in gas masses. Few astronomers agreed with Rosse - like Stephen Alexander , who wrote in 1851: "The Milky Way and the stars in it form a spiral and several (perhaps 4) arms and a central star cluster" [].

The nebulae weren't the only work Lord Rosse worked in. He also devoted considerable energy to studying the temperature of the moon's 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 construction to the Newton telescope

Parsons (similar to Herschel) invented an alternative to the side view of the Newton telescope because its mirrors were big enough for it. Meyers Konversationslexikon wrote in 1885:

“In the 'giant telescopes' by Herschel and Lord Rosse, the mirrors of which were 1-2 m in diameter, such a second mirror and thus the loss of light it caused was avoided by a simple trick. The concave mirror (see Fig. 5) is namely a little inclined relative to the axis of the tube, so that the image comes to lie close to the edge of the mirror and can be viewed there through an ocular lens. Of course, the observer's head partially steps in front of the opening of the tube, but this is of little importance given the large diameter of the mirror. "

Lord Rosse was also active in charity and tried to alleviate the misery in his country, see his writing Letters on the state of Ireland (London 1847).

literature

Rosse, William Parsons . In: Encyclopædia Britannica . 11th edition. tape 23 : Refectory - Sainte-Beuve . London 1911, p. 745 (English, full text [ Wikisource ]).

Web links

Commons : William Parsons, 3rd Earl of Rosse - Album with pictures, videos and audio files

Entry to Parsons; William (1800-1867); 3rd Earl of Rosse in the Archives of the Royal Society , London

Individual evidence

^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. (PDF file) Royal Society of Edinburgh, accessed March 27, 2020 .
^ Foreign members of the Russian Academy of Sciences since 1724: Parsons, William, Lord Rosse. Russian Academy of Sciences, accessed March 27, 2020 (Russian).
^ GD Roth: History of Astronomy . P. 102
↑ Telescope (dioptric and catoptric) . In: Meyers Konversations-Lexikon . 4th edition. Volume 6, Verlag des Bibliographisches Institut, Leipzig / Vienna 1885–1892, p. 151.

predecessor	Office	successor
Lawrence Parsons	Earl of Rosse 1841-1867	Lawrence Parsons

personal data
SURNAME	Parsons, William, 3rd Earl of Rosse
ALTERNATIVE NAMES	Parsons, William
BRIEF DESCRIPTION	Irish astronomer
DATE OF BIRTH	June 17, 1800
PLACE OF BIRTH	York
DATE OF DEATH	October 31, 1867
Place of death	Birr Castle

[1] Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. (PDF file) Royal Society of Edinburgh, accessed March 27, 2020 .

[2] Foreign members of the Russian Academy of Sciences since 1724: Parsons, William, Lord Rosse. Russian Academy of Sciences, accessed March 27, 2020 (Russian).

[3] GD Roth: History of Astronomy . P. 102

[4] Telescope (dioptric and catoptric) . In: Meyers Konversations-Lexikon . 4th edition. Volume 6, Verlag des Bibliographisches Institut, Leipzig / Vienna 1885–1892, p. 151.