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Cas A

Assumedly in the year 1667 a supernova exploded which was observed by nobody then. Cas A is the youngest supernova remnant known to us in our galaxy. Actually with this small distance the explosion should have been rather noticeable. Probably it was hidden behind gas masses ejected by the progenitor star and by dense interstellar matter. The progenitor star could have been a Wolf-Rayet Star.

Cassiopeia A, so its full name, is the strongest radio source in the sky outside our solar system. That in turn could be an evidence that the supernova indeed was much brighter than the later computed 250 000 solar luminosities. Supernovae can be a billion times brighter as the Sun for a short time. So the absorbing gas here must have been very photoresistant.

The expanding shell has a temperature of 10 to 50 million kelvin.

Constellation: Cassiopeia
Distance: 11 000 light-years
Visual magnitude as supernova: max. 5-6
Mass progenitor star: 15 * Sun

Back: List of Special Stars part 2
    Cas A
The good visible central star isn't identified yet. Supposedly it is a Neutron Star or a Black Hole.
X-ray-photo: NASA/CXC/SAO

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