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Question on Supernova Explosions



 
 
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  #1  
Old February 20th 05, 08:17 AM
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Default Question on Supernova Explosions

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?

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

I remember reading long ago that impact zones of supernovae are roughly
100 - 500 light years across (diameter), is that correct? (500 light
years diameter on 100,000 light years diameter gives a factor of 200)

What is it for hypernovae?

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

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?

Thanks,
Michael M. Terra

  #2  
Old February 20th 05, 08:44 AM
Brian Tung
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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
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
  #3  
Old February 20th 05, 03:10 PM
Davoud
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:
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?

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


Brian Tung:
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.


The December 27, 2004, outburst from the magnetic neutron star SGR
1806-20, _50,000 LY distant_, had an impact zone that included the
Earth. Radiation that it spewed forth compressed the Earth's ionosphere
for a short period, disrupting long-range HF radio communications.

"Whoppingly bright," said Dr. Brian Gaensler, an astronomer at the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "It
gave off more energy in 0.2 seconds than the Sun does in 100,000 to
200,000 years." (Quoted by the NYT.) It outshone the all the rest of
the stars in the Milky Way at certain wavelengths.

SGR 1806-20 is believed to contain about 1.5 solar masses in a sphere
about 20 KM in diameter; it rotates every 7.5 seconds, a leisurely rate
for a neutron star. Amazingly, following the outburst SGR 1806-20
remained intact, still rotating at the same rate.

Aaaah, the power of gravity!

Davoud
  #4  
Old February 20th 05, 04:11 PM
Chris L Peterson
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On Sun, 20 Feb 2005 09:10:49 -0500, Davoud wrote:

The December 27, 2004, outburst from the magnetic neutron star SGR
1806-20, _50,000 LY distant_, had an impact zone that included the
Earth...


The OP didn't define "impact zone". Brian chose to take it as the radius
where there would be significant biological impact on planets with
atmospheres. You've adopted a less extreme definition. Of course, one
could easily argue that any place where a supernova is detectable is
inside the impact zone.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #5  
Old February 20th 05, 05:31 PM
Brian Tung
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Chris L Peterson wrote:
The OP didn't define "impact zone". Brian chose to take it as the radius
where there would be significant biological impact on planets with
atmospheres. You've adopted a less extreme definition. Of course, one
could easily argue that any place where a supernova is detectable is
inside the impact zone.


Yes, that's right. I really didn't know what was meant by "impact zone"
in the original post. The least arbitrary meaning I came up with, given
the context that we are, after all, human beings asking the question,
was the one I used.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
  #6  
Old February 20th 05, 06:58 PM
Davoud
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The December 27, 2004, outburst from the magnetic neutron star SGR
1806-20, _50,000 LY distant_, had an impact zone that included the
Earth...


Chris L Peterson:
The OP didn't define "impact zone". Brian chose to take it as the radius
where there would be significant biological impact on planets with
atmospheres. You've adopted a less extreme definition. Of course, one
could easily argue that any place where a supernova is detectable is
inside the impact zone.


Brian Tung:
Yes, that's right. I really didn't know what was meant by "impact zone"
in the original post. The least arbitrary meaning I came up with, given
the context that we are, after all, human beings asking the question,
was the one I used.


Just to be perfectly clear: it wasn't my intention to criticize Mr.
Tung's response in any way, but only to point out the remarkable power
of the SGR 1806-20 outburst. I find it remarkable that, at 50,000 LY,
it had an effect that was detectable not only by specialized detectors
on earth satellites, but by anyone who listens to short-wave radio
broadcasts -- quite a few millions of people around the world, in spite
of the advent of satellites and the Internet!

Davoud
  #7  
Old February 20th 05, 09:46 PM
RichA
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On Sun, 20 Feb 2005 09:10:49 -0500, Davoud 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?

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


Brian Tung:
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.


The December 27, 2004, outburst from the magnetic neutron star SGR
1806-20, _50,000 LY distant_, had an impact zone that included the
Earth. Radiation that it spewed forth compressed the Earth's ionosphere
for a short period, disrupting long-range HF radio communications.

"Whoppingly bright," said Dr. Brian Gaensler, an astronomer at the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "It
gave off more energy in 0.2 seconds than the Sun does in 100,000 to
200,000 years." (Quoted by the NYT.) It outshone the all the rest of
the stars in the Milky Way at certain wavelengths.

SGR 1806-20 is believed to contain about 1.5 solar masses in a sphere
about 20 KM in diameter; it rotates every 7.5 seconds, a leisurely rate
for a neutron star. Amazingly, following the outburst SGR 1806-20
remained intact, still rotating at the same rate.

Aaaah, the power of gravity!

Davoud


At that density, is there anything else besides gravity holding it
together?
-Rich
  #8  
Old February 24th 05, 06:03 AM
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Astronomers, thanks for all the replies.

If an 'average size' Type II Supernova explodes at a distance of say 50
light years from the sun, can you describe some of the direct and
longterm affects/impacts on earth, plant and animal life, atmosphere,
weather, oceans, magnetic field, etc.., i.e. what are they?

Would it matter what direction the 'blast' came from, e.g. would the
damage on the backside of the earth be a lot less?

If at 50 light years, it would extinguish all life, what then about 100

or 200 light years away?

With regards,
Michael M. Terra

  #10  
Old February 25th 05, 12:27 AM
Stupendous_Man
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wrote:

If an 'average size' Type II Supernova explodes at a distance of say

50
light years from the sun, can you describe some of the direct and
longterm affects/impacts on earth, plant and animal life, atmosphere,
weather, oceans, magnetic field, etc.., i.e. what are they?


You can find some numbers which may help you to answer your
question at

http://stupendous.rit.edu/richmond/answers/snrisks.txt

Would it matter what direction the 'blast' came from, e.g. would the
damage on the backside of the earth be a lot less?


No. The high-energy electromagnetic radiation -- X-rays
and gamma-rays -- from the event would be spread out over a
matter of days to weeks. The Earth would rotate many times
while being bathed in radiation.

If at 50 light years, it would extinguish all life,
what then about 100
or 200 light years away?


As you will see at the above URL, I estimate that
a Type II supernova would have to be closer than 10 pc
to make a significant change in the Earth's environment;
that corresponds roughly to "closer than 30 light years."
There are no known Type II progenitors within this distance.

Michael Richmond

 




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