Living Art, I was waiting such an answer from you ! :slfg: :slfg: :slfg:
Thunderous applause for Bdspider and MarkLB : it's Tycho's Supernova Remnant.
Discovered by Tycho Brahe, a danish astronomer. Visible to the naked eye, it appeared on november 11, 1572, in the constellation Cassiopeia, 8,000 / 9,800 light-years from us. . As bright as Jupiter, they could see it even at noon in a clear sky.
Here's what he reported :
The gas shell we can see on the picture, is now expanding at about 9000 km/s...
Here's a video :
- http://youtu.be/RtCKVangyD8