Goal: To understand how the sun works

Objectives:

1) Journey to the center of the sun!

Spaceship Sol• Scheduled departure time: 5 min.

• Please fasten seatbelts.

What color is

The sun?

a) Yellow

b) Orange

c) Blue

d) White

e) Red

Spaceship Sol• Scheduled departure time: 4 min.

• Prepare for departure.

Is the sun

a “star”?

a) Yes

b) No

Liftoff! Travel distance: 93 million miles

Heliosphere:

Solar Wind

speed: 390.0 km/s

density:

7 protons/cm3

Outside temp:

292K

68 F

Density outside:

Almost 0.

Outside temp:

400K

262 F

Density outside:

10 protons/cm3

Outside temp:

450K

352 F

Density outside:

28 protons/cm3

Outside temp:

604K

618 F

Distance to sun:

20 million miles

Density outside:

140 protons/cm3

Outer area of the corona - the start of the solar wind

Outside temp:

1208K

1705 F

Distance to sun:

5 million miles

Density outside:

2200 protons/cm3

Corona: millions of degrees!

Outside temp:

2415K

3879 F

Distance to sun:

1.25 million miles

(0.8 million from the surface)

Density outside:

35000 protons/cm3

Corona

Outside temp:

1 million K!

100k miles from the surface

Chromosphere

Outside temp:

10000K

1k miles from the surface

CORONAL MASS EJECTION!!!

Rotation of the sun.

The sun rotates every 26-28 days, depending on where on the sun you are.

Why could this be important?

Photosphere

Outside temp:

5800K

Surface!

Density:

1% of air.

All of the sun’s light that we see comes from here.

Question:

If we fly in onto that sunspot, will it be dark or light?

Photosphere

Outside temp

5800K

Surface (400 km deep)!

Sunspots are light!

They are 1-2k

cooler, so

compared to

the rest of the

sun, they

appear to be

darker.

Granules:

Convection

cells. Kind of

like in a pot

of boiling

water.

Welcome to the sun! http://www.nasa.gov/mpg/118091main_other_loop_sm.mpg

Warning: breathing apparatus will be required as the sun is made of 74% Hydrogen, 25% Helium, and only 1% other stuff.

Question: where on or in the sun is there a solid surface to land on?

How dense is the sun?

• A) About the density of air

• B) About the density of water

• C) About the density of lead

• D) more dense than any material on earth

How dense is the sun?

• B) About the density of water

• The average density of the sun is only 40% more than the density of water.

• Density of the sun is 1.4 g/cm3, vs. 1.0 for water.

Convective zone:

Starts at the bottom of the photosphere and goes down for about 200k km.

Temperature:

6k on the top

2 million on the bottom!

Density gets up to 1/10th the density of water.

Energy is transported through convective cells.

Radiative Zone

• Average density is water.• This is a stable region, kind of like the Stratosphere on

the earth.• Starts 200k km below the photosphere, and ends 200k

km above the center of the sun. That is 50% of the radius of the sun!

• Energy is transferred by radiation.• Temperature ranges from 2 to 7 million degrees Kelvin!

• How long do you think it takes light to pass through the Radiative Zone?

Time for light to pass through the Radiative Zone:

• Light will be scattered from 1 particle to the next (sort of like light scattered by water, but even worse, and imagine a pool of water about 400k km deep!).

• Even though light travels at the speed of light, it STILL takes 1 MILLION years for a photon of light to get through this layer!

The Core!

• The core is the engine of the sun and is the bottom 100-200k km of the sun.

• In the core, the force of gravity is pretty intense.

• Temperature: up to 15 million degrees Kelvin!

• Density: up to 150 times the density of water!

Hydrostatic Equalibrium• Here there is a tug of war. • Gravity is pulling down• Gas pressure and radiative (light) pressure are

pushing up. • The sun has to produce lots of energy just to

keep itself from collapsing under its own weight! • This is called Hydrostatic Equilibrium.

• Very special and important things happen when this equilibrium are broken, but more on that later in the course

Conclusion

• The sun is a wild, crazy, and often violent place.

• It has weather that puts any weather the earth has to same.

• Coronal mass ejections, if pointed right at the earth, can do serious damage to satellites, and possibly even our electric grid!