Transcript Goal: To understand how the sun works

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!