| Why/how do stars explode?|
|Question Date: 2017-09-28|
Stars explode when they run out of fuel.
A star is a balance between gravity that
sucks everything IN and high temperature due to
nuclear reactions that push everything OUT.
So, when a star runs out of FUEL, gravity wins
the balance and the star collapses in
(implodes), and then the imposition turns
itself inside out and blows the star apart.
This is called a supernova and it is very
As stars get older, they waste material from
the nuclear reactions that power stars builds up
in the stars' cores. The sun is burning
hydrogen and accumulating helium, and will
eventually begin burning helium to create carbon
and oxygen. The sun isn't massive enough to burn
oxygen, so the oxygen will sit there like a lump
and never burn. More massive stars can burn the
oxygen to create silicon, and the silicon to make
iron, but no star, no matter how massive, can
burn iron. If a star builds up a lump of iron with
a mass of 1.44 times that of the sun, then the
pressure that the iron atoms make on each-other
will not be enough to hold them up, and they will
collapse. This collapse releases energy, so
much energy in fact that the rest of the star
can't contain it, and it explodes.
Very large stars explode when they run out
of fuel. Stars burn hydrogen (H) in their core
throughout their lifetime. We call it "burning",
but what is really happening is that H atoms
are crashing together to form helium (He) atoms. H
and He are what make up stars. Eventually a
star will run out of H fuel in the core, and will
have nothing left to burn. This is just like when
you have a bonfire and you run out of wood to burn
- the fire dies out. When this happens in a star,
some of the mass from the outer parts of the star
sink to the middle. This new mass in the middle of
the star is very hot and heavy, so it also starts
burning to create the heavier elements like
carbon, oxygen, and every element up to the mass
of iron. These elements are much denser than
hydrogen, so it causes the star to become
unstable and it collapses on itself under its own
gravity in an explosion called a supernova.
Inside a supernova, even more elements are
born! The periodic table is arranged by mass of
the elements: everything from H to Fe is made
in a star, and everything heavier than Fe
is made during the supernova explosion. So
all of the elements that make up the earth and
even you were made inside a star or during a
supernova! Only stars that are 5x heavier
than our sun will go through a supernova.
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