Supernova 1604, also known as Kepler’s Supernova, Kepler’s Nova or Kepler’s Star, was a supernova that occurred in the Milky Way, in the constellation Ophiuchus. As of April 2010, it is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 6 kiloparsecs or about 20,000 light-years from Earth. Visible to the naked eye, it was brighter at its peak than any other star in the night sky, and all the planets (other than Venus), with apparent magnitude −2.5. It was visible during the day for over three weeks.
The supernova was first observed in northern Italy on October 9, 1604. Johannes Kepler began observing it on October 17. It was subsequently named after him because of his book on the subject entitled De Stella nova in pede Serpentarii (“On the new star in Ophiuchus’s foot”, Prague 1606).
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.
via SN 1604