22 March

Argelander was a German astronomer who established the study of variable stars as an independent branch of astronomy and is renowned for his catalogue listing the positions and brightness of 324 188 stars of the northern hemisphere above magnitude +9.

He studied at the University of Königsberg, Prussia, where he was a pupil and later the successor of Friedrich Wilhelm Bessel. In 1837, Argelander published the first major investigation of the Sun's motion through space. In 1844 he began studies of variable stars. He died on 17 February 1875.

1394: On 22 March 1394, Ulug Beg was born.

Beg was an important Mongol scientist and mathematician, and the greatest astronomer of his time. He began to build an observatory in 1428 in Samarkand. His observations revealed a number of errors in the computations of the 2nd-century astronomer Ptolemy, whose figures were still being used.

Begs's star map of 994 stars was the first new one since that of Hipparcos. Beg was assassinated by his son on 27 October 1449, and after this the observatory fell into ruin by 1500, rediscovered only in 1908.