Download The Sun abbreviated

The Sun, our favorite star!
The Sun is the basis
for all of our
knowledge of stars.
Why?
WE CAN SEE IT REALLY WELL.
Today we will take a
journey to the center of the
Sun, starting with what we
can see…
…and ending up deep in
the core.
Overview of Solar Structure
(aka, our Sun as a jawbreaker)
Main Parts:
 Corona
 Chromosphere
 Photosphere
 Convection Zone
 Radiative Zone
 Core
The Sun is made of
mostly HYDROGEN and
HELIUM
The Corona
• Outer layer of the
Sun
• Millions of degrees
but very diffuse
• Extends millions of
kilometers into
space
• Hot and energetic,
gives off lots of
xrays!
Coronal Mass Ejections and
Magnetic Activity
• Corona is
heated by the
Sun’s magnetic
field, which
stores a lot of
energy
Sometimes, it
releases this
energy, causing
space weather!
In detail…
This twisting leads to the
loopy structures we see!
BE AMAZED!
Earth to scale.
Yes, really.
The Chromosphere
• Just below the
corona and also
marked by
energetic
magnetic
activity:
– Flares
– Prominences
(those loopy
things)
– Spicules
• Lots of emission
lines!
The Photosphere
• This is the “surface”
of the Sun
• Not a real surface,
because the Sun is
made of gas…
… but where the
sun becomes
opaque and we
can’t see any
deeper!
sunspots
The photosphere has some
interesting features too…
Sunspots:
Regions where magnetic
field pokes through the
photosphere.
Sunspots are cooler than
surrounding stuff, so they
look dark!
Granules:
Where the roiling, boiling
convection zone underneath
bubbles up.
Next up, the interior of the Sun…
• Energy is generated in the core but
how does it get out and end up as
sunshine?
The next two layers of the Sun are all
about getting the energy being made
in the core out into space!
How does energy get from
one place to another?
1.
Convection
2.
Conduction
3.
Radiation Diffusion
Convection and Radiation Diffusion
are most important for the Sun!
Convection
Hot stuff
rises…
Cool stuff
sinks!
Hot water goes up to the surface
while cool water sinks down -- cool
water then gets heated and rises
a.k.a: BOILING
Conduction
Metal of the pan
heats by
conduction…
…heat travels
through the
atoms of the pan
Not very important for
stars!
Radiative Diffusion
The photons
“diffuse” outwards,
heating the gas as
they go.
Ionized
gas
• Photons can “scatter” off of unbound
electrons
• When they scatter, the photons
share their energy with the electrons
• The electrons get hotter
The Convective Zone
Photosphere
The Convective
Zone is the layer
just under the
photosphere
Convective “cells”:
As seen from the top, these are
the granules we see in the
photosphere
The Radiative Zone
Here, photons
bounce around in
a “random walk”
Ionized
gas
Eventually they
make it out of the
radiative zone,
but it takes a
long, long time!
At last, we reach the core…
The core is
where the
Sun’s energy
is made!
The core is so
hot and has such
high pressure
that FUSION can
take place
But wait: Why are the
central pressures so high?
???
Gravity pulls the
surface of the Sun in,
but the Sun doesn’t
collapse…
What is pushing
back???
The pressure
of the gas
layers below.
Gas Pressure keeps the Sun
from collapsing
Pressure
This applies to all
layers of the Sun.
Gravity pulls outer
layers in, Gas
Pressure pushes
them out.
Why does high pressure in the core
lead to Fusion?
High
Temperature
and Density
allows nuclei to
interact!
Nuclei can FUSE
together:
“Nuclear Fusion”
Energy Production in Stars:
The short version.
p
p
p
n
p
p
4H
n
p
+
Energy
1He
4 Hydrogen Atoms fuse to make 1
Helium Atom and a bunch of
energy.
How does fusion generate
energy?
The Sun is made mostly of
HYDROGEN and HELIUM
4 protons in H are
slightly heavier
than the 2 protons
+ 2 neutrons in He
Some mass converts
to energy!
Sunshine = Energy from Fusion
E=
Energy
2
mc
Mass
Speed of
Light
Speed of light is BIG-- so a little
mass can turn into a LOT of energy!
Okay, let’s get out of the
core. It’s hot in here.
A QUICK REVIEW:
(layers not to scale)
Corona
Chromosphere
Photosphere
Convective Zone
Radiative Zone
Core