Supernova 1604, also known as Kepler's Supernova or Kepler's Star, was a supernova in the Milky Way, in the constellation Ophiuchus. As of 2004, it is the last supernova to have been unquestionably observed in our own galaxy, occurring no greater than 6 kiloparsecs from Earth. A "naked-eye" supernova, it was brighter at its peak than any other star in the night sky, and all the planets too, with apparent magnitude −2.5.
Since 6 kiloparsecs is ca. 20,000 light-years the cosmic event itself happened no earlier than 18,000 BC.
The supernova was first observed on October 9, 1604. The German astronomer Johannes Kepler first saw it on October 17, but he studied it so extensively that the supernova was subsequently named after him. His book on the subject was entitled De Stella nova in pede Serpentarii (On the new star in Ophiuchus's foot).
It was the second supernova to be observed in a generation (after SN 1572 seen by Tycho Brahe in Cassiopeia). No further supernovae have since been observed with certainty in the Milky Way, though many others outside our galaxy have been seen.
The supernova remnant resulting from this supernova is considered to be one of the "prototypical" objects of its kind, and is still an object of much study in astronomy.
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