the sun, our favorite star! we can see it really well. the sun is the basis for all of our knowledge...
TRANSCRIPT
The Sun, our favorite star!The Sun, our favorite star!
WE CAN SEE IT REALLY WELL.WE CAN SEE IT REALLY WELL.
The Sun is the basis for all of our knowledge of stars. Why?
Today we will take a journey to the center of the Sun, starting with what we can see…
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.
…and ending up deep in the core.
Overview of Solar Structure(aka, our Sun as a jawbreaker)
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 CoronaThe 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!
• 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 Coronal Mass Ejections and Magnetic Activity
• Corona is heated by the Sun’s magnetic field, which stores a lot of energy
• Corona is heated by the Sun’s magnetic field, which stores a lot of energy
Sometimes, it releases this
energy, causing space
weather!
Sometimes, it releases this
energy, causing space
weather!
In detail…In detail…
This twisting leads to the loopy structures we see!This twisting leads to the loopy structures we see!
BE AMAZED!BE AMAZED!
Earth to scale.Yes, really.
The ChromosphereThe Chromosphere
• Just below the corona and also marked by energetic magnetic activity:– Flares– Prominences
(those loopy things)
– Spicules
• Lots of emission lines!
• Just below the corona and also marked by energetic magnetic activity:– Flares– Prominences
(those loopy things)
– Spicules
• Lots of emission lines!
The PhotosphereThe 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!
• 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…
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…
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!
• 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?
How does energy get from one place to another?
1. Convection
3. Radiation Diffusion
2. Conduction
Convection and Radiation Diffusion are most important for the Sun!
ConvectionConvection
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
ConductionConduction
Metal of the pan heats by conduction…
…heat travels through the
atoms of the pan Not very important for stars!
Radiative DiffusionRadiative Diffusion
The photons “diffusediffuse”
outwards, heating the gas
as they go.• Photons can “scatter” off of
unbound electrons• When they scatter, the photons
share their energy with the electrons
• The electrons get hotter
Ionized gas
The Convective Zone The Convective Zone
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
Photosphere
The Radiative ZoneThe Radiative Zone
Ionized gas
Here, photons bounce around in a “random walk”
Eventually they make it out of the
radiative zone, but it takes a
long, long time!
At last, we reach the core…
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?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
Gas Pressure keeps the Sun from collapsing
PressureThis 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?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.
Energy Production in Stars:
The short version.
4 Hydrogen Atoms fuse to make 1 Helium Atom and a bunch of energy.
p
p p
pnn
p
p+ Energy
4H 1He
How does fusion generate energy?
How does fusion generate energy?
4 protons in H are slightly heavier than the 2 protons + 2 neutrons in He
Some mass converts to
energy!
The Sun is made mostly of HYDROGEN and HELIUM
Sunshine = Energy from FusionSunshine = Energy from Fusion
E = mc2E = mc2Energy
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.
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