Cassiopeia A: Flamsteed's Supernova of 1680

A Type Ia supernova is generated by the collapse of a white dwarf star. White dwarves are small and exceptionally dense stars- they are the cores of stars that have shed their outer envelopes of gas in pretty Planetary Nebulae fashion. If left alone, these white dwarves would cool (after billions of years) and become the dark kernels of former sunlike stars. However, should a white dwarf have a nearby star from which it could accrete gas (and add mass)- the extra matter pushes the white dwarf beyond the limit of stable existence and it explodes in dramatic fashion.

Re-discovered in 1952 by radio astronomy, the remains of this star still glow in many wavelengths of light. Later the 200in Palomar telescope detected the dim remains of this star in optical wavelengths. Interestingly this image with amatuer equipment far exceeds images in optical light from the telescopic giants of yesteryear. This gas is expanding at velocities of millions of miles per hour. Currently the shell of gas is around 10 light years in diameter and has a temperature of around 50 million degrees. Cass A is considered the most recent supernova explosion that has been observed in our galaxy. Unfortunately interstellar dust may have dimmed the initial explosion so that it went unnoticed by most of humanity. Like the Crab Nebula, these kinds of star deaths infuse heavy elements of matter into the galaxy... elements that may later coalesce to become planets and people.