Michael Terra wrote:
The Milky Way is approximately 100,000 light years across (diameter).
The last supernova explosion in our galaxy was sighted by Kepler in
1604. Of course the size of a supernova or a hypernova explosion can
vary.

Questions:
How many light years away was the 1604 explosion and roughly where was
it in our galaxy relative to the sun?

It was near the galactic center, which would make it about 25,000
light-years away.

What was the estimated rough size (diameter) of its impact zone?

That would depend somewhat on whether it was a Type I or Type II
supernova. Type I supernovae, which result from a white dwarf exceeding
the Chandrasekhar limit of 1.4 solar masses (this may vary slightly
depending on composition), are more energetic than Type II supernovae,
which result from the collapse of a massive star. A Type II supernova
would be deadly to human life out to a distance of perhaps 10 to 20
light-years; a Type I supernova maybe a factor of two or three further.
I don't think these distances are known to great precision.

I understand there were 6 supernovae in our galaxy in the last 1000
years.

Something like that. There might have been more, but they could have
been hidden by gas clouds in the galactic plane.

Any information you can provide or point me to on size, date and
location, etc., of the 5 before the one observed by Johannes Kepler in
1604?

Sure. Before Kepler's supernova in Ophiuchus in 1604, there was Tycho's
supernova in Cassiopeia in 1572. Before that, the Chinese and Japanese
reported a probable supernova (of course, they didn't use that term)
in Cassiopeia in 1181, and also a supernova in Taurus in 1054, which
yielded the Crab Nebula. The Chinese also reported a supernova in Lupus
in 1006. Those five are the only ones in the Milky Way proper that I
am aware of.

There was, of course, the Type II supernova in Dorado, in the Large
Magellanic Cloud, in 1987.

Brian Tung
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