6th November 1572 – Supernova!
On this date a ‘new-star’ was seen in the constellation of Cassiopeia. Detected by multiple observers across Europe and in China, it was probably first seen by the German astronomer Wolfgang Schüler of Wittenberg (b. ? d.1575). The new star was a supernova, specifically a Type 1a event Although its technical identification in SN1572, it is also named Tycho’s supernova after the Danish astronomer Tycho Brahe. Brahe studied the event extensively and in 1573 published a book: De Nova et nullius aevi momoria prius visa stellar of his observations and analyses. Within this, Brahe reported no discernible observational parallax and thus showed how the Aristolean cosmology (Earth centre universe, unchanging beyond the sphere on the Moon’s orbit) was incorrect.
Ce jour une nouvelle étoile a été observée dans la constellation de Cassiopée. Vue par de nombreux observateurs en Europe et en Chine c’est peut-etre Wolfgang Schüler de Wittenberg (b. ? d.1575) qui est le premier à l’avoir observée. La nouvelle étoile était une supernova de Type 1a. Nomée SN1572 elle est également nomée la supernova de Tycho Brahe, l’astronome danois. Brahe a beaucoup étudié l’événement et en 1573 il a publié un livre sur ses observations et analyses: De Nova et nullius aevi momoria prius visa stellar. Dans ce livre Brahe a montré que la cosmologie aristotélicienne était incorrecte.
Supernova are very rare. The best-known supernova is undoubtedly the event of 1054 which led to the Crab Nebula. Since that time only 3 have been seen within our own galaxy (in 1181, 1572 and 1604) although two others in 1667 and 1868 have subsequently been detected but were not observed at the time. The most recent, nearby, supernova was the 1987 event within the Small Magellanic Cloud (a satellite galaxy to our own).
Composite X-ray and optical wavelength image of SN1572
In optical wavelengths the remnant is virtually invisible.
Courtesy NASA/CXC/Rutgers/K.Eriksen et al http://chandra.harvard.edu/photo/2011/tycho/
Around 9000 light years away, SN1572 is a classical Type 1a supernova. These occur when an evolved star, a white dwarf, accumulates additional matter from a companion star. A white dwarf does not generate energy by nuclear fusion but it does not gravitationally collapse because of electron degeneracy pressure.
Many stars occur in binary systems (where there are two stars orbit their mutual centre of gravity). The orbit can decay and material can be disrupted from the white dwarf’s companion and accumulate onto the solid surface of the white dwarf. Alternatively, the binary system can merge which gives similar effects. When this happens the electron degeneracy pressure ‘fails’ and an explosive collapse to a neutron star, or black hole, results. (We look at stellar evolution and these end-points in our book on solar physics.)