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A supernova is a stellar explosion that happends in result of the death of a
massive star. It involves the expulsion of the stars outer layers. A supernova is a
relatively rare event in our galaxy, it happens about every 50 years. When a
supernova explodes, briefly it can outshine an entire galaxy, and give out as
much energy as the sun will in a life- time, and the explosion is equivalent to the
power in a 1028 megaton bomb (i.e., a few octillion nuclear warheads).
How Do Supernovae Occur
Supernovae occur when the star’s core fusion process runs out of fuel. The
outward pressure drops, causing the gravitational pull to become unbalanced.
The core starts to condense under gravity because there is a lack of outward
pressure. When the core shrinks too much, the star swells and grows, iron atoms
are crushed together, temperatures reach billions of degrees Celsius, and then a
series of nuclear reactions is unleashed. The supernova produces a giant shock
wave that throws matter into space at 9,000 to 25,000 miles per second.
Type Ia, Ib and Ic Supernovae
There are several classes of supernovae; they are classified by the kinds of
elements that are seen in their spectra. Type 1a does not contain helium and
have a silicon line in their spectrum. They are thought to be formed in some
binary star systems by the explosion of a carbon oxygen white dwarf. Due to an
unknown companion star, there is a high level of mass deposited on the white
dwarf. When the density of the white dwarf reaches 2 x 109 g/cm, the dwarf
collapses into a neutron star or black hole and the collapse causes the carbon
and oxygen atoms to fuse. This fusion produces a shockwave and the dwarf star
is blown apart. It also contains hydrogen unlike Type II. Type 1 b and 1c contain
helium, but do not have the silicon line. Type Ib is thought to be formed when a
massive star that is made mainly of helium, carbon, nitrogen or oxygen
collapses, also called a Wolf-Rayet star.
Type II
The supernova occurs when the nuclear fuel of the star runs out. If the star’s iron
core is massive enough, when it collapses, it will explode in a supernova. Some
scientists think that type 1b supernovae are actually type 2. The hydrogen was
probably blown away by the huge star’s strong stellar winds before the star
exploded which explains the lack of hydrogen in its spectrum.
Black Holes and Neutron Stars
When the supernova is done exploding, as an effect of the large transfer of
matter and energy, there is a very different star left. This star is called a spinning
neutron star. Neutron stars produce radio waves in a steady stream or in random
bursts. But if a star is massive enough, it can leave behind something more. For
this to happen though, the star must be 10 times the size of the sun at least. So
the supernova leaves a large core, and with no energy to fuse it doesn’t have any
outward pressure, and that causes it to be very unbalanced. The star gets
engulfed in it’s own gravity and becomes a black hole.
Observation History
Supernovae have been observed over history, and although supernovae only
occur in our galaxy every 50 years, several hundred are observed every year
from other nearby galaxies. Some important supernovae that have happened
over the years are Keplers Supernova, 1604, the supernovae that produced the
Crab Nebula, 1054, and the one that happened in the Large Magellanic Cloud in
1887. The first supernova recorded was in 185 AD, called SN 185. It was
recorded by Chinese Astronomers and was in the sky for 8 months.
When a supernova occurs, the remnants remain. Remnants are what are left
from a supernova explosion. They are still studied years after they are released
into space, and they are what heat up the gases and dusts between the stars,
and they also help new stars form and add elements to space clouds. They throw
matter in space at about 9,000 to 25,000 miles per second. Another effect of
supernovae is that they place a lot of the heavy elements in the universe, and
produce a lot of the material in our universe. On earth, supernovae can be seen
for weeks in the sky. Iron that is found in supernovae made our planet and even
ourselves. Unfortunately, some people think that a supernova will destroy our
solar system. 