Delivery-Date: Thu Apr 27 14:31:13 2000
Date: Thu, 27 Apr 2000 14:30:58 -0400
From: Stupendous Man <richmond@a188-l009.rit.edu>
Subject: Re: questions about supernovae
To: "Lauren C." <muse@lightlink.com>
Cc: mwrsps@ritvax.isc.rit.edu
Message-id: <200004271830.OAA21429@a188-l009.rit.edu>
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  Lauren,

     Some of the questions you ask can be answered by reading material
at the following sites:

     Lots of pictures of recent supernovae:
        http://www.ggw.org/asras/supernova.html 

     Effects of a supernova on life on nearby planets:
        http://a188-L009.rit.edu/richmond/answers/snrisks.txt 


> ok, 1) what is a supernova

  A star which explodes.  There are two main mechanisms which can
cause a star to explode:

      a. one type of star is called a "white dwarf" -- it is 
         very small (only about the size of the Earth) and 
         very dense.  If a companion star dumps lots of material
         onto a white dwarf, so that the mass of the white dwarf
         grows bigger than a certain limit, then nuclear reactions
         occur inside the white dwarf and blow it apart
         (like a giant thermonuclear bomb)

      b. very massive stars -- more than 10 times the mass of our
         Sun -- build up big cores of iron at their centers.  When
         such a star runs out of fuel, the core of iron collapses
         on itself, shrinking in a few seconds to a tiny ball,
         only ten miles or so across.  This ball is made of neutrons.
         The ball rebounds a bit just after it forms, and sends a
         shock wave outwards through the star, which shoves all
         the outer layers into space.


>         2) what are the effects while it is happening if there are any

      In brief, the star becomes very hot (over 100,000 degrees),
and starts expanding at 3,000 to 10,000 kilometers per second.
It emits lots of radiation: X-rays, UV, visible light, infrared,
and radio waves.

>         3) what are the effects after it happens

      There's a big shell of gas expanding at high speed away
from where the star used to be.  In the second type of supernova,
there may be a neutron star left over at the center of the explosion;
or there may be a black hole; or there may be nothing.

>         4) are there any warning signs to a supernova

      Not really.  In the second type of supernova, it takes a few 
hours after the collapse of the core for the shock wave to reach
the surface of the star.  It is possible to detect particles called
neutrinos, produced at the moment of the collapse, during this period
of a few hours, and so gain a VERY SHORT advance notice.  But it
wouldn't be enough to run away successfully.

>          5)how is the space around the explosion effected

      It is filled with lots of radiation, and eventually gas from
the outer layers of the star pass through it.

>         6)why have there only been 3 supernovas in our galaxy?

      Um, there have been more than that observed in our galaxy.
Read 

       http://a188-L009.rit.edu/richmond/answers/historical.html

or a book called "The Historical Supernovae", by Clark and Stephenson.

 
>         7) why is it more common in others

       Huh?  I don't undestand this question.

>         8) what are supernova rements?

       "Remnants" are whatever is left over after a supernova occurs.
In some cases, there may be a neutron star or black hole at the 
center of the explosion.  In all cases, there is a big mass of hot
gas expanding outwards at high speeds.  We can detect the hot gas
for several tens of thousands of years after the explosion.

>         9) how long do the rements stay

        Well, we can detect remnants in our own galaxy which are
many thousands of years old.  But when we look at other galaxies,
the remnants are so distant that they disappear from our view
after a few decades or so.

>         10) could you tell me about the diffrence between  type1 and type2
> supernovas

        See the answer to question 1.  The first class of explosions,
due to white dwarfs which accrete too much extra material, are called
"Type Ia" supernovae.   The second class of explosions, in which
a massive star runs out of fuel and its core collapses, are called
"Type II" supernovae.  You can find a fuller description of the types
of supernovae at

         http://a188-l009.rit.edu/richmond/answers/sntypes.txt

> thanks a bunch its a real help

        You are welcome.


-- 
-----                                      
Michael Richmond                   "This is the heart that broke my finger."
mwrsps@rit.edu                     http://stupendous.rit.edu/richmond/