page_title: SN 1572
section_title: The supernova
hierarchical_section_title: SN 1572 / The supernova
caption_attribution_description: English: Photometry of Tycho
context_page_description: SN 1572, or B Cassiopeiae, was a supernova of Type Ia in the constellation Cassiopeia, one of eight supernovae visible to the naked eye in historical records. It appeared in early November 1572 and was independently discovered by many individuals.
  The remnant of the supernova has been observed optically but was first detected at radio wavelengths; it is often known as 3C 10, a radio-source designation, although increasingly as Tycho's supernova remnant.
context_section_description: The supernova was classified as type I on the basis of its historical light curve soon after type I and type II supernovae were first defined on the basis of their spectra.  The X-ray spectrum of the remnant showed that it was almost certainly of type Ia, but its exact classification continued to be debated until the detection of a light echo in 2008 gave final confirmation that it is a normal type Ia.
  The classification as a type Ia supernova of normal luminosity allows an accurate measure of the distance to SN 1572.  The peak absolute magnitude can be calculated from the B-band decline rate to be −19.0±0.3.  Given estimates of the peak apparent magnitude and the known extinction of 1.86±0.2 magnitudes, the distance is 3.8+1.5
  −0.9 kpc.
caption: Light curve of Tycho's supernova, reconstructed from historical observations (via the Open Supernova Catalog)
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