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Observatory's Historic Data Used to Constrain Sunspot Cycle

Rainer Arlt, an astrophysicist working at Potsdam Observatory in Germany, and co-workers have used observations made at the Armagh Observatory more than 200 years ago to resolve a long-standing mystery regarding the Sun and its approximately 11-year cycle of sunspot numbers.

Research published by Rudolph Wolf in the nineteenth century indicated that there was a long minimum between solar cycles 4 and 5, corresponding to the years 1784 to 1799. However, Arlt's work, published recently in the German international journal Astronomische Nachrichten and the prestigious Astrophysical Journal Letters (USA), indicates that a cycle commenced in 1793.

Arlt used observations by Revd James Archibald Hamilton, first Astronomer at the Armagh Observatory and Rector of Kildress, near Cookstown, Co. Tyrone and his assistant William Gimingham, to identify a previously unknown maximum in the sunspot numbers to find the missing cycle. This result has importance in understanding solar-terrestrial relationships. In particular, it highlights the role played by the Sun and how it affects the Earth's climate, and it emphasizes the value of such historic material and the importance of retaining it for future use.

FOR FURTHER INFORMATION PLEASE CONTACT: Srividya Subramanian or John McFarland at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; sriat signarm.ac.uk; jmfat signarm.ac.uk

See also:
The solar observations at Armagh Observatory in 1795–1797 - PDF

A Solar Cycle Lost in 1793–1800: Early Sunspot Observations Resolve the Old Mystery - PDF

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Last Revised: 2009 August 20th
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