Our Sun Our Star Image credit: JAXA OU-L P SC 100 Spring, 2009
1/81
Slide 2
109 Earths would fit across the diameter of the sun Diameter:
1,400,000 km = 864,000 miles = 4.5 light-seconds 1,300,000 Earths
could fit inside! OU-L P SC 100 Spring, 2009 2/81
Slide 3
Mass: 2 x 10 30 kg or 330,000 times Earths mass Density: 1.41
g/cm 3 OU-L P SC 100 Spring, 2009 3/81
Slide 4
What planet has this same composition? OU-L P SC 100 Spring,
2009 4/81
Slide 5
Surface temp: 5800 K, 5500 o C, 11,000 o F Luminosity total
energy output at all wavelengths = 4 x 10 26 watts/second (more
than 6 moles of 100 watt light bulbs) OU-L P SC 100 Spring, 2009
5/81
Slide 6
4.5 million metric tons of H are converted to He every second
Expected lifetime: 10 billion years Distance from earth: 1 A.U. =
93,000,000 miles = 150,000,000 km = 8.33 light minutes OU-L P SC
100 Spring, 2009 6/81
Slide 7
1 rotation takes 27.5 days at the equator, but 31 days at the
poles! (Differential rotation) How was this determined? OU-L P SC
100 Spring, 2009 7/81
Slide 8
Image Credit: SOHO OU-L P SC 100 Spring, 2009 8/81
Slide 9
OU-L P SC 100 Spring, 2009 9/81
Slide 10
The Suns Structure 3 Interior Layers The core produces the
energy The radiative zone The convective zone 3 Atmosphere Layers
Photosphere Chromosphere Corona OU-L P SC 100 Spring, 2009
10/81
Slide 11
OU-L P SC 100 Spring, 2009 11/81
Slide 12
OU-L P SC 100 Spring, 2009 12/81
Slide 13
The Core 16,000,000 K (a stars core must be at least 8,000,000
K to start fusing H to He. no real atoms, only a soup of protons,
electrons, and some larger atomic nuclei (He and C). all radiation
produced is gamma () OU-L P SC 100 Spring, 2009 13/81
Slide 14
Radiative Layer not hot enough for fusion normally transparent
gases have become opaque to light. Photons of light bounce from one
atom to another in a random walk, like a gigantic pinball game.
OU-L P SC 100 Spring, 2009 14/81
Slide 15
Radiative Layer A given photon may take 100,000 years to reach
the next layer. As photons travel, they slowly lose energy,
shifting down towards the X- ray region of the spectrum.
Temperature of this layer falls with increasing distance from core.
OU-L P SC 100 Spring, 2009 15/81
Slide 16
Convective Zone Still hot enough to be opaque to light.
Currents of gas move vertically, like water boiling in a pan.
Energy is transported by convection, not by radiation. This layer
is like earths mantle. OU-L P SC 100 Spring, 2009 16/81
Slide 17
OU-L P SC 100 Spring, 2009 17/81
Slide 18
The tops of convection cells can be seen near the sunspots.
They are called granules, or granularity. OU-L P SC 100 Spring,
2009 18/81 Image Credits: SOHO/NASA/ESA and JAXA
Slide 19
OU-L P SC 100 Spring, 2009 19/81 Granularity movie
http://apod.nasa.gov/apod/ap090405.html
Slide 20
The Photosphere Innermost of the suns atmosphere layers. Gas
cools enough that it becomes transparent to light. Sunlight
originates from this layer. This is the surface that we see. Only
300 km thick. OU-L P SC 100 Spring, 2009 20/81
Slide 21
Actual color of photo- sphere is slightly greenish. OU-L P SC
100 Spring, 2009 21/81
Slide 22
The Chromosphere 2 nd atmosphere layer. Glows in red H- light
(the red line from the level 3 level 2 electron transition in H
atoms). Filters out the greenish color of the photosphere, so we
see yellow light. Several thousand kilometers thick. OU-L P SC 100
Spring, 2009 22/81
Slide 23
OU-L P SC 100 Spring, 2009 23/81 Image Credit:
SOHO/NASA/ESA
Slide 24
The Corona Millions of kilometers thick, but extremely low
density. Suns magnetic field agitates corona, raises temperature
back up to about 2,000,000 K. Only visible during a total solar
eclipse, or from space with specially designed telescopes. OU-L P
SC 100 Spring, 2009 24/81
Slide 25
OU-L P SC 100 Spring, 2009 25/81
Slide 26
Features on the Suns Surface Produced by suns magnetic field.
Prominences & flares. Sunspots Coronal Holes Coronal Mass
Ejections OU-L P SC 100 Spring, 2009 26/81
Slide 27
Differential Rotation Differential rotation winds up and
tangles the magnetic field, resulting in surface storms. Process is
not very well understood. OU-L P SC 100 Spring, 2009 27/81
Slide 28
OU-L P SC 100 Spring, 2009 28/81
Slide 29
OU-L P SC 100 Spring, 2009 29/81
Slide 30
Theres still a lot we dont know Why doesnt the sun have
activity all the time? The magnetic field should be winding up and
tangling constantly. Does the sun produce the same strength of
magnetic field all the time? Is it structured differently at some
times than at others? OU-L P SC 100 Spring, 2009 30/81
Slide 31
Slide 32
Prominences & Flares When a loop of the suns magnetic field
projects out from the surface, some of the hot gas from the
photosphere may flow along the field lines in arcs or loops, called
prominences. OU-L P SC 100 Spring, 2009 32/81
Slide 33
A loop prominence lets us visualize the magnetic field. OU-L P
SC 100 Spring, 2009 33/81 Image Credit: TRACE/NASA
Slide 34
Slide 35
OU-L P SC 100 Spring, 2009 35/81 Image Credit:
SOHO/NASA/ESA
Slide 36
Flares Sometimes, the magnetic field lines disconnect from the
sun. Hot gas trapped inside the new loop of magnetic field travels
outward from the sun as a solar flare. OU-L P SC 100 Spring, 2009
36/81
Slide 37
OU-L P SC 100 Spring, 2009 37/81 Image Credit:
SOHO/NASA/ESA
Slide 38
Sun spots Where the loops of magnetic field penetrate the suns
surface, they cool it. Sunspots occur in pairs of (+) and (-)
polarity. Sunspots are still about 3500 K hot enough to melt
anything on the earth, but 2000 K cooler than the surrounding
surface. OU-L P SC 100 Spring, 2009 38/81
Slide 39
OU-L P SC 100 Spring, 2009 39/81
Slide 40
OU-L P SC 100 Spring, 2009 40/81
Slide 41
Umbra Penumbra OU-L P SC 100 Spring, 2009 41/81
Slide 42
Sunspot Cycle The number of sunspots varies from year to year,
along with the overall magnetic activity of the sun. Were used to
hearing of an 11 year cycle. Thats only for the overall number of
sunspots. OU-L P SC 100 Spring, 2009 42/81
Slide 43
Sunspot Cycle The real cycle is 22.2 22.4 years long, and
includes 11 years of the magnetic field with (+) polarity, then
another 11 years with (-) polarity. We also see sunspots migrate
from high latitudes to nearer the equator as the cycle progresses.
OU-L P SC 100 Spring, 2009 43/81
Slide 44
OU-L P SC 100 Spring, 2009 44/81
Slide 45
OU-L P SC 100 Spring, 2009 45/81 You are here
Slide 46
Sometimes, the cycle quits! 1645 to 1715, few sunspots
observed. Maunder Minimum. Mini ice age across Europe. OU-L P SC
100 Spring, 2009 46/81
Slide 47
OU-L P SC 100 Spring, 2009 47/81
Slide 48
Coronal Holes Actual holes or windows in the suns corona Solar
wind can easily blow through. When one of these points towards the
earth, the velocity and density of the solar wind increases. OU-L P
SC 100 Spring, 2009 48/81
Slide 49
A coronal hole a window to the interior. OU-L P SC 100 Spring,
2009 49/81 Image Credit: SOHO/NASA/ESA
Slide 50
You can see the solar wind blowing thru several coronal holes.
OU-L P SC 100 Spring, 2009 50/81 Image Credit: SOHO/NASA/ESA
Slide 51
One of the worst events During the active phase, the magnetic
field sometimes gets tangled up so tight, that the sun blows off a
portion of its entire corona. This is a coronal mass ejection
(CME). A CME can be very damaging to electrical systems on the
earth. OU-L P SC 100 Spring, 2009 51/81
Slide 52
CME in progress OU-L P SC 100 Spring, 2009 52/81 Image Credit:
SOHO/NASA/ESA
Slide 53
http://sohowww.nascom.nasa.gov/ Watch a CME in progress OU-L P
SC 100 Spring, 2009 53/81
Slide 54
CMEs are made up of charged particles, have magnetic and
electrical fields. Fields cause electrical systems to build up
abnormally high voltages. In the winter of 2000-01, a CME knocked
out power to all of eastern Canada & the northeastern US for
nearly a week. OU-L P SC 100 Spring, 2009 54/81
Slide 55
Satellites are damaged by CMEs, so we spend $ on special
shielding. Communications, especially broadcast radio & TV, can
be knocked out by CMEs for hours at a time. OU-L P SC 100 Spring,
2009 55/81
Slide 56
Missions to the Sun SOHO Ulysses Genesis TRACE Hinode (Sunrise
- Japans version of SOHO) OU-L P SC 100 Spring, 2009 56/81
Slide 57
SOHO (Solar and Heliospheric Observatory) a joint venture
between ESA & NASA. Looks continuously at the sun from a fixed
spot in space. Observes flares, CMEs & comets falling into the
sun! OU-L P SC 100 Spring, 2009 57/81
Slide 58
sohowww.nascom.nasa.gov/ OU-L P SC 100 Spring, 2009 58/81
Slide 59
Ulysses designed to orbit over the suns poles & provide a
perspective that we cant get from earth. This is ESAs logo. OU-L P
SC 100 Spring, 2009 59/81
Slide 60
Ulysses mission ulysses.jpl.nasa.gov/ OU-L P SC 100 Spring,
2009 60/81
Slide 61
Genesis Mission The Genesis mission was designed to orbit the
sun and collect samples of the solar wind. It returned these
particles to Earth for examination. Genesis orbited at a point
called the L1 Lagrange point - a place in space where earths
gravity exactly cancels the suns gravity. OU-L P SC 100 Spring,
2009 61/81
Slide 62
genesis.lanl.gov/ OU-L P SC 100 Spring, 2009 62/81
Slide 63
Genesis Solar Wind Sampling Mission
genesismission.jpl.nasa.gov/
Slide 64
The TRACE spacecraft (Transition Region and Coronal Explorer)
provides images like these.
Slide 65
How does the sun make its energy? Fusion of H to He occurs in a
process called the proton-proton chain. Larger, heavier stars fuse
H to He using C, N, and O (CNO cycle) OU-L P SC 100 Spring, 2009
64/81
Slide 66
A review of the symbols a proton: 1 1 H or p + (a proton is the
nucleus of a normal hydrogen atom.) neutron: n o electron: e -
positron: e + (a positively charged electron or antimatter) OU-L P
SC 100 Spring, 2009 65/81
Slide 67
more particlesactors on the stage neutrino: (a tiny, nearly
massless particle with no charge that barely interacts with normal
matter.) gamma ray: (the highest energy form of light) OU-L P SC
100 Spring, 2009 66/81
Slide 68
Isotopes / nuclear symbols What does 4 2 He mean? How many p +,
n o in 56 26 Fe? neutrons are the nuclear glue that hold a nucleus
together. OU-L P SC 100 Spring, 2009 67/81
Slide 69
The first collision of three The first step in the p-p chain is
the collision of 2 protons. One proton immediately shatters,
becoming a neutron. The new neutron gets rid of its (+) charge by
giving off a positron (e + ) and a neutrino ( ). The resulting p +
n o is a deuterium nucleus. OU-L P SC 100 Spring, 2009 68/81
Slide 70
p + e + p + n o p + e - OU-L P SC 100 Spring, 2009 69/81
Slide 71
A 2 nd collision Another high speed proton (p + ) collides with
the deuterium nucleus (p + n o ) and sticks. This collision gives
off a gamma ray ( ) The result is a 3 2 He nucleus: (p 2 n o ) +2.
OU-L P SC 100 Spring, 2009 70/81
Slide 72
p + n o (p 2 n o ) +2 p + OU-L P SC 100 Spring, 2009 71/81
Slide 73
Collision #3 Two 3 2 He nuclei (p 2 n o ) +2 collide head- on
to form a normal helium nucleus, 4 2 He. In the process, they give
off 2 protons. OU-L P SC 100 Spring, 2009 72/81
Slide 74
(p 2 n o ) +2 p + (p 2 n o 2 ) +2 (a He nucleus) p + (p 2 n o )
+2 The 2 protons start the chain over. OU-L P SC 100 Spring, 2009
73/81
Slide 75
Heres the overall p-p chain OU-L P SC 100 Spring, 2009 74/81
Image Credit: atropos.as.arizona.edu/
Slide 76
What goes in: 6 protons (H nuclei) What comes out: 1 He nucleus
2 protons 2 positrons 2 neutrinos 2 gamma rays (4 gamma rays if you
count the annihilation of the positrons) OU-L P SC 100 Spring, 2009
75/81
Slide 77
The Neutrino Problem Until recently, we could only detect about
1/3 of the neutrinos we ought to observe from the p-p chain. For
the past several years, solar scientists werent sure if their model
was correct. OU-L P SC 100 Spring, 2009 76/81
Slide 78
The Neutrino Problem Neutrinos are detected by the flashes of
light (scintillations) they produce as they interact with water
molecules in huge tanks underground (to minimize interference from
cosmic rays.) OU-L P SC 100 Spring, 2009 77/81
Slide 79
Super Kamiokande neutrino detector, Japan. OU-L P SC 100
Spring, 2009 78/81 Image Credit: pbs.org
Slide 80
Neutrino Problem Solved! Neutrinos change type (or flavor)
while theyre on their way from the sun. Counting these other
flavors of neutrinos gives a total thats just whats expected. This
also proves that neutrinos have mass (tiny, but measurable.) OU-L P
SC 100 Spring, 2009 79/81
Slide 81
Sun in 3 different ultraviolet wavelengths. OU-L P SC 100
Spring, 2009 80/81 Image Credit: SOHO/NASA/ESA
Slide 82
Additional Credits solar-heliospheric.engin.umich.edu/
solar.physics.montana.edu/ helio.estec.esa.nl/ulysses/
www.bbso.njit.edu/ csep10.phys.utk.edu/ Peters Planetarium Image
Library, for images not otherwise credited.
Slide 83
NASAs twin Stereo spacecraft, launched in 2006, observe the sun
from different points in space, allowing us to see ALL of the sun
for the first time! 83
Slide 84
The Solar Dynamics Observatory or SDO now complements SOHO with
more modern instruments. It is the most recent addition to the
solar fleet, launched in Feb. 2010. 84
