### Bessel Deduces Sirius Companion **Date**: August 10, 1844 • **Location**: Berlin, Germany From measurements of its motion, German astronomer Friedrich Wilhelm Bessel deduced that Sirius, the brightest star in the night sky, had an unseen companion. Friedrich Wilhelm Bessel was a German astronomer, mathematician, physicist, and geodesist. He was the first astronomer who determined reliable values for the distance from the Sun to another star by the method of parallax. Certain important mathematical functions were first studied systematically by Bessel and were named Bessel functions in his honour.

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