Alvan Graham Clark makes the first ever…

January 1862 CE

Alvan Graham Clark makes the first ever observation of a white dwarf star, Sirius B, while testing a new 18.5-inch (470 mm) aperture great refractor telescope on January 31, 1862, in Cambridgeport, Massachusetts made by his father's company.

This discovery of Sirius B, or affectionately "the Pup", proves an earlier hypotheses (Friedrich Bessel in 1844) that Sirius, the brightest star in the night sky with an apparent magnitude of −1.46, has an unseen companion disturbing its motion.

Clark has used the largest refracting telescope lens in existence at the time, and the largest telescope in the United States, to observe the magnitude 8 companion.

Clark's 18.5 inch refracting telescope is now delivered to his customer, the landmark Dearborn Observatory of Northwestern University in Evanston, Illinois, where it is still being used today.

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Cambridgeport Middlesex Massachusetts United States View →

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Massachusetts, Commonwealth of (U.S.A.) View → United States of America (US, USA) (Washington DC) View → Illinois, State of (U.S.A.) View →

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Italian unification View →

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Technology View → Astronomy View → Optics View →

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