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He was the first astronomer to identify a supernova in 1572 (SN 1572).
Pope St. Pius V reigned from 1566 to 1572.
SN 1572 or Tycho's Supernova was a supernova type Ia, in the constellation Cassiopeia
1572 is an integer and so is not changed by rounding to a thousandth.
1, 2, 3, 4, 6, 12, 131, 262, 393, 524, 786, 1572