| If the sun is a star, why doesn't it explode?|
|Question Date: 2016-01-10|
The heat that the sun's fusion reaction produces
makes all of the atoms and molecules inside of it
move quickly (atoms are always in motion and move
faster when hotter) and in many cases a fusion
reaction would lead to an explosion. But the sun
is also very heavy which means that the gravity
pulling all of the sun's hot gases towards the
center of the sun is also very strong. That
gravitational force is 28 times higher at the
sun's surface than the gravity we feel on earth's
surface. There are two competing forces: due
to the heat it tries to expand, but due to gravity
it tries to contract. These two balance each
other out so the sun stays the same size.
Good question. The Sun is a stable object
because there is a balance of two forces that are
equal. The explosive force is that associated
with nuclear reaction in its interior where by
Hydrogen is transformed to Helium plus some
energy. This is thermal pressure making the
reaction products want to disperse
(explosion). On the other hand, the force
of gravity is strictly attractive and IT is
causing the Hydrogen and Helium of the sun to want
to shrink down...gravity pulls everything IN
towards the center. So these two forces are
opposed and they equal each other in absolute
value...one pushes OUT and the other pulls IN...
Hence the Sun appears stable.
Force balances are very important for example, if
gravity is pulling you towards the center of the
earth why don't you sink there? That’s
because there is a pressure force that the earth
exerts on your feet pushing you up! Gravity down
and pressure up and hence you can stand still and
not accelerate because the sum of gravity down and
pressure up equals zero.
You're right, the Sun is a star. But stars
aren't exploding all the time. Stars evolve,
growing and changing over millions of years. After
their very last phase, they will eventually
Think of the stars in the night sky. These
stars spend all their time burning their fuel and
evolving into bigger stars. Each of them will
explode someday, but we'll be lucky just to see
one of them explode.
The sun (like any star) has enough mass that
its gravity holds it together. It would explode if
not for its gravity.
Stars exploding despite their gravity (supernovae)
are actually powered by the gravity as the
star's interior collapses to become a something
much denser than a star. The sun does not have
enough mass (and thus enough gravity) to do this.
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