William Parsons, 3rd Earl of Rosse |
William Parsons
Lord Rosse (June 17, 1800
– October 31, 1867) was an Irish
astronomer.
He became the third Earl of Rosse when his father died in 1841.
In the 1840s, he built his "Leviathan of Parsonstown" 72-inch telescope at Birr, Ireland (then called "Parsonstown") in County Offaly, which was for many decades the largest telescope in the world. The telescope mirror was made
from speculum metal. Because it tarnished so rapidly in the damp
climate, the mirror had to be repolished every six months, and so Lord Rosse had two mirrors built so that one could be used
while the other was being repolished. Building of the telescope had to be suspended during the Great Potato Famine, but in 1847 it was put into service. The light-gathering ability exceeded expectations, enabling 18th magnitude stars to be
observed for the first time.
Lord Rosse carried out pioneering astronomical studies and discovered the spiral nature of some nebulas, today known to be spiral galaxies. The first spiral galaxy he
detected was M51, and his drawings of it closely resemble modern photographs (today it is
known as the Whirlpool Galaxy).
He named the Crab Nebula, based on an earlier drawing made with his older
36-inch telescope in which it resembled a crab. A few years later, when the 72-inch telescope was in service, he produced an
improved drawing of considerably different appearance, but the name stuck anyway.
In addition to his astronomical pursuits, he served as a member of Parliament, an Irish
representative peer, president of the Royal Society (1849-1854), and chancellor of the University of Dublin (beginning in 1862).
He had four sons. The eldest, Lawrence Parsons, succeeded him as Earl of Rosse and continued some astronomical
observations; another son, Charles Algernon
Parsons, is known for his commercial development of the steam
turbine.
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