|How does nuclear fusion fuels our sun?|
|Question Date: 2013-09-16|
When I think about the sun, I like to think of
the chorus from a song titled Why Does The Sun
Shine? This lyrics for this song were written way
back in 1951, but they're still true.
The sun is a mass of incandescent gas
A gigantic nuclear furnace
Where hydrogen is built into helium
At a temperature of millions of degrees
Technically speaking, nuclear fusion doesn't fuel
our sun. Two elements comprise almost all of the
fuel that our sun burns via nuclear reactions;
those elements are hydrogen and helium, the two
lightest and most abundant elements in the
Universe. A hydrogen atom is made of one proton
and one electron. A helium atom is made of two
protons, two neutrons, and two electrons.
Let's talk nuclear fusion. What happens when
you fuse two things together? They become one
different thing. Nuclei are the centers of atoms,
made of particles called neutrons and protons
around which the atoms' electrons blanket.
Nuclear fusion is the process of fusing two nuclei
together and creating one nucleus. The nuclei we
start with may or may not be of the same element,
but the nucleus we create cannot be of the same
element. Remember that elements are unique in that
the atoms of a given element have a distinct
number of protons, neutrons, and electrons
compared to other elements.
We know the sun has a bunch of fuel in the form
of hydrogen and helium. We also know that nuclear
fusion consumes this fuel and gives off tremendous
amounts of energy. What's specifically happening?
The Sun is so massive that the lightest elements
in the Universe cannot escape it's gravitational
pull. Hydrogen and helium are trapped at the
center of the Sun, and the immensity of the Sun's
gravity forces four hydrogen atoms to fuse
together into one helium atom and release the
energy that keeps the Sun burning and our skin
"But wait a minute!" you might say. "How do you
just GET energy out of fusing stuff together?"
Come to find out, the mass of a helium atom
(4.00260 atomic mass units) is less than the mass
of four hydrogen atoms (1.00794 * 4 = 4.03176
atomic mass units). Ever hear of the equation E =
m*c2? Einstein informed us that mass is
equivalent to energy; energy is equal to mass
times the speed of light squared. You can get a
lot of energy from the conversion of a tiny bit of
mass. The difference in mass between a helium atom
and four hydrogen atoms generates enough energy to
keep the sun's nuclear furnace stoked and prevent
it from gravitationally collapsing on itself.
This difference in mass isn't all good, though.
Because the Sun is gradually getting lighter,
scientists predict that in 5.5 billion years it
will run out of fuel and burn out. So enjoy it
while it lasts!
The sun undergoes what is known as
proton-proton fusion. The gas that comprises the
sun is very hot, which means that hydrogen atoms
are moving around very quickly. When two protons
collide at such a high speed, they are able to
fuse to become a helium atom. There are actually a
few intermediate steps in the process, but
overall, the products that result are a helium
atom and a photon, which carries a lot of energy.
The energy of the photon is absorbed by the gas in
the sun, which results in the gas being heated and
further propagating the process.
Nuclear fusion in the sun is a continuous reaction
that can happen because of the immense temperature
and pressure (mostly temperature) in the sun's
interior. The process of nuclear fusion releases
immense amounts of energy in the form of heat, and
it is this heat that slowly bleeds out of the
sun's core and into the upper layers and finally
to the surface, where it is emitted as light
because the temperature is still hot enough to
shine at visible wavelengths even on the coldest,
My name is Mike. Thank you for your wonderful
question "How does nuclear fusion fuel our sun?"
The sun is an absolutely ginormous mass of
interstellar gasses-mostly hydrogen and
helium-that has been burning for about 4 or 5
billion years. The sun has so much mass, that it
has incredibly strong gravity and magnetic fields
that cause nuclear fusion to occur in the sun´s
core. Overall, nuclear fusion in our sun combines
two hydrogen atoms (the smallest and lightest
atoms) together to form one helium atom (a
slightly larger atom). When this combination
occurs, energy is released in the form of gamma
rays, which are very high energy rays of
radiation. These gamma rays heat up the
surrounding molecules, and the gamma rays
eventually decay and are converted into the
visible light, UV light, Infrared light, and X-ray
light that finally makes its way to earth. Back
inside the sun, the intense heat caused by the
gamma rays, and the byproducts of the nuclear
fusion reaction, heat the sun to incredible
temperatures, and help stabilize the continual
reaction inside the core of the sun.
I have also included a link to a webpage that
explains the chemical chain reaction that occurs
in nuclear fusion. I encourage you to take a look
through it if you are interested!
here to see, please
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