A1 15 Our Sun

The Solar Interior
LACC: §14.3, 15.2, 15.3
• Know what powers the sun
• Understand the Solar Neutrino Problem
• Know the Solar interior

An attempt to answer the “big questions”: what is
the sun? how does it effect us?

Thursday, April 15, 2010 1

The Sun: Wow! Sheet
Energy generated in the Sun's core takes a million years to reach its surface. Every
second 700 million tons (1/(3 billion billionth) of the sun’s total mass) of hydrogen are
converted into helium ash. In the process 5 million tons of pure energy is released;
therefore, as time goes on, the Sun is getting lighter.
Mass (tons) 2.19x1027
Mass (Earth = 1) 332,830 Principal chemistry (1.)
Equatorial radius (km) 695,000 Hydrogen 92.10%
Equatorial radius (Earth = 1) 108.97 Helium 7.80%
Mean density (gm/cm 3) 1.41 Oxygen 0.061%
Rotational period (days)! 25-36* Carbon 0.030%
Escape velocity (km/sec) 618.02 Nitrogen 0.084%
Luminosity (ergs/sec) 3.83x1033 Neon 0.076%
Magnitude (Vo) -26.8 Iron 0.0037%
Mean surface temperature! 10,800°F Silicon 0.0031%
Core temperature! 27,000,000°F Magnesium 0.0024%
Core density (gm/cm3) 150 Sulfur 0.0015%
Core pressure (atm) 340,000,000,000 All others 0.0015%
Age (billion years) 4.5 1. % by # of atoms abundances

* The Sun's period of rotation at the surface varies from approximately 25 days at the
equator to 36 days at the poles. Deep down, below the convective zone, everything
appears to rotate with a period of 27 days.

http://www.solarviews.com/eng/sun.htm

The Proton-Proton Chain

http://astro.unl.edu/classaction/loader.html?ﬁlename=animations/sunsolarenergy/
fusion01.swf&movieid=fusion01&width=550&height=550&version=6.0.0


The Atom, e.g. He 4

http://www.bio.miami.edu/~cmallery/150/chemistry/c8.2x5.helium.jpg


Subatomic Particles of
Interest
Particle Symbols Charge Mass
Protons p, p+, 1H, H+ +1 1.0073
Neutrons n, n0 0 1.0087
Electrons e, e+, β+ -1 0.0005
Positron e- , β - +1 0.0005
Neutrino ν 0 0?
Gamma Ray γ 0 0
Alpha Particle α, 4He, He2+ +2 4.0015


p-p Chain: Energy Production
The evidence is strong that the sun is "burning" H to make He:
4H + 2e- --> He4 + 2 neutrinos + 6 photons
In this reaction, the ﬁnal particles have less internal energy than the
starting particles. Since energy is conserved, the extra energy is
released as energy of motion of the nuclei and electrons in the
solar gas, the production of photons [pure energy] and, ﬁnally, the
energy of the neutrinos, which just zip right out of the Sun. That is
the gas gets hotter and has lots of photons (and neutrinos). The
amount of energy involved is 26 MeV (26 million eV) each time the
reaction above happens. (By comparison, CH4 + 2O2 --> CO2 + 2H2O
results in 5.5 eV of energy.)
Why do we think that this is what goes on?

•
Energy output of millions of eV per reaction is needed if the Sun
has been producing energy at the observed rate over billions of years.

•
The reactions exist. (They have been studied in the laboratory.)

•
There is a consistent step-by-step theory for the reaction.
Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu

http://zebu.uoregon.edu/~soper/Sun/fusion.html

Solar Neutrino Problem
Super-
Kamiokande, a
neutrino
detector in
Japan, holds
50,000 tons of
ultrapure water
surrounded by
light tubes.
http://www.scidacreview.org/0601/html/astro.html


Solar Neutrino Problem
Over the years scientists
have considered two
possible explanations of
the solar neutrino problem:
1. Perhaps we don't
understand the Sun
well enough. Maybe a
better theory of the
internal structure of the
Sun would predict fewer
neutrinos, in agreement
with the measurements.
2. Perhaps we don't
understand neutrinos
well enough; maybe
they have some
features beyond the
standard theory of
neutrinos that account
for the problem.

http://www.cora.nwra.com/~werne/eos/text/neutrino.html


The Solar Neutrino
Problem

Particles in the Standard
Model of particle physics:
The Standard Model
contains 3 neutrinos of
definite flavor, and a set
of corresponding anti-
particles.

http://conferences.fnal.gov/lp2003/forthepublic/neutrinos/index.html


Hydrostatic Equilibrium

http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter16.html

Solar Interior

http://sprg.ssl.berkeley.edu/%7Eabbett/sun1.html


Solar Interior
The photons produced in nuclear reactions take about a million years to
move from the core to the surface. The photons scatter off the dense gas
particles in the interior and move about a centimeter between collisions. In each
collision they transfer some of their energy to the gas particles. By the time
photons reach the photosphere, the gamma rays have become photons of
much lower energy---visible light photons. Because the photons now reaching
the surface were produced about a million years ago, they tell us about the
conditions in the core as it was a million years ago. The other particle produced in
nuclear reactions has a less tortuous path out of the core.

A neutrino is a massless (or very nearly massless) particle that rarely interacts
with ordinary matter. Neutrinos travel extremely fast---the speed of light if they
have zero mass or very close to the speed of light if they have a small mass.
Because they travel so fast and interact so rarely with matter, neutrinos pass
from the core of the Sun to the surface in only two seconds. They
take less than 8.5 minutes to travel the distance from the Sun to the Earth. If you
could detect them, the neutrinos would tell you about the conditions in the Sun's
core as it was only 8.5 minutes ago (much more current information than the
photons!).
http://www.astronomynotes.com/starsun/s4.htm


Solar Core

http://fas.org/irp/imint/docs/rst/Sect20/A5a.html

Solar Interior
Core Radiation

• p-p chain occurs • photons travel
• convection • vacuum, gasses
Radiative zone Convection

• photon random walk • bulk ﬂuid ﬂow
• radiation • liquid, gasses
Convection zone Conduction

• convection cells • individual molecules collide
• convection • solids


The Solar Interior
LACC: §14.3, 15.2, 15.3
• Know what powers the sun: Nuclear Fusion,
the p-p chain, 4H + 2e- --> He4 + 2 ν + 6 γ

• Understand the Solar Neutrino Problem: It
seems that neutrinos can change ﬂavor
• Know the Solar interior: core, radiative zone,
convection zone, photosphere



HW: Franknoi, Morrison, and Wolff,
Voyages Through the Universe, 3rd ed.

• Ch 15, p354: #4

• Ch 14: Tutorial Quizzes accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
ﬁd=M20b&product_isbn_issn=9780495017899&discipline_number=19

• Ch 15: Image Analysis Quizzes accessible
from: http://www.brookscole.com/cgi-brookscole/
course_products_bc.pl?

Due beginning of next class period.


Solar Surface and Atmosphere
LACC: §14.3, 15.2, 15.3

• Know the sun’s atmosphere
• Know solar surface features
• Know how the sun affects the earth



Solar Atmosphere

K = Kelvin
°C = Celsius
°F = Fahrenheit

K = °C + 273.15
°F = 1.8°C + 32°

So, at high temperature,
°F ≅ 1.8°C

At very high temperatures,
°F ≅ 1.8K

http://rst.gsfc.nasa.gov/Sect20/A5a.html

Solar Features

http://ircamera.as.arizona.edu/NatSci102/lectures/sun.htm

Solar Features: Sunspots

http://www.astro.wisc.edu/
http://starchild.gsfc.nasa.gov/docs/
~sparke/ast103/
StarChild/questions/question17.html
lecture11.html

Granules are individual convection cells.


Solar Features: Sunspots
Sunspots are dark, planet-sized regions that appear on
the "surface" of the Sun. Sunspots are "dark" because
they are cooler than their surroundings. A large
sunspot might have a central temperature of 4,000 K
(about 3,700° C or 6,700° F), much lower than the 5,800
K (about 5,500° C or 10,000° F) temperature of the
adjacent photosphere. Sunspots are only dark in
contrast to the bright face of the Sun. If you could cut an
average sunspot out of the Sun and place it elsewhere in
the night sky, it would be about as bright as a full moon.
Sunspots have a lighter outer section called the
penumbra, and a darker central region named the umbra.
Sunspots form over periods lasting from days to
weeks, and can persist for weeks or even months
http://www.windows.ucar.edu/
before dissipating. The average number of spots visible
tour/link=/sun/images/
on the face of the Sun is not constant, but varies in a
sunspots_earth_size_big_jpg_i
multi-year cycle. Historical records of sunspot counts,
mage.html&edu=high
which go back hundreds of years, verify that this sunspot
cycle has an average period of roughly eleven years.
http://www.windows.ucar.edu/tour/link=/sun/
atmosphere/sunspots.html&edu=high


Solar Features:
Sunspot Cycle

Although astronomers have observed the fairly regular rise and fall of
sunspot counts in this 11-year cycle for several centuries, there have
also been disruptions in this pattern. The largest well-documented
disruption was an era that lasted from about 1645 to 1715 during which
almost no sunspots were seen. This long lull is known as the Maunder
Minimum. Curiously, Europe and parts of North America were struck by
spells of remarkably cold weather at roughly the same time.
http://www.windows.ucar.edu/tour/link=/sun/activity/solar_variation.html

Solar Features:
Sunspots--Cause
Sunspots are magnetic -- they occur
in pairs where one is a north pole
while the other is a south pole.
Every 11 years, the more western parts
of sunspot pairs will change from
magnetic N to magnetic S (or vice
versa). (From Chaisson & McMillan,
Astronomy Today)

http://ircamera.as.arizona.edu/NatSci102/
lectures/sun.htm


Solar Features:
Sunspots and Magnetism

Every 11 years the sun’s
magnetic ﬁeld snaps back
to situation #1. But, when it
snaps back, the North and
South magnetic poles will be
reversed.

So the sunspot cycle is
every 11 years, but the solar
magnetic ﬁeld cycle is every
22 years.

http://www.windows.ucar.edu/tour/link=/sun/atmosphere/
sunspot_form_jpg_image.html&edu=high

Solar Features: Prominences
(and Filaments)
One of the most spectacular solar sights
is a prominence. A solar prominence is
a cloud of solar gas held above the
Sun's surface by the Sun's magnetic
field. Last month, NASA's Sun-orbiting
SOHO spacecraft imaged an
impressively large prominence hovering
over the surface, pictured above. The
Earth would easily fit under the hovering
curtain of hot gas. A quiescent
prominence typically lasts about a
month, and may erupt in a Coronal
Mass Ejection (CME) expelling hot gas
into the Solar System. Although
somehow related to the Sun's changing
magnetic field, the energy mechanism
that creates and sustains a Solar
prominence is still a topic of research.
http://apod.nasa.gov/apod/ap040330.html


(and Filaments)
Hot gas frequently erupts from the
Sun. One such eruption produced the
glowing filament pictured above,
which was captured in 2000 July by
the Earth-orbiting TRACE satellite.
The filament, although small
compared to the overall size of the
Sun, measures over 100,000
kilometers in height, so that the entire
Earth could easily fit into its
outstretched arms. Gas in the
filament is funneled by the complex
and changing magnetic field of the
Sun. After lifting off from the Sun's
surface, most of the filamentary gas
will eventually fall back.

http://antwrp.gsfc.nasa.gov/apod/ap040725.html


(and Filaments)

http://www.veoh.com/browse/videos/category/technology/watch/v2191746WPa6CtKC


Flares vs Filament (Prominence)

Solar flare (171Å) Solar flare (1600Å) Solar flare (white light)
The two images on the left were
taken on 25 June 2000, around
07:37UT (the images were
rotated, so that north is to the
left). The image on the left
shows a filament in the process
of being ejected from the Sun,
with cool (dark) and hot (bright;
around 1.5 million degrees)
material at opposite ends of the
long, nearly vertical structure.
http://soi.stanford.edu/results/SolPhys200/Schrijver/TRACEpodoverview.html

Solar Features: Flares
Solar flares are essentially huge explosions on the
Sun. Flares occur when intense magnetic fields on
the Sun become too tangled. Like a rubber band that
snaps when it is twisted too far, the tangled
magnetic fields release energy when they "snap".
Solar flares emit huge bursts of electromagnetic
radiation, including X-rays, ultraviolet radiation, visible
light, and radio waves. The energy emitted by a solar
flare is more than a million times greater than the
energy from a volcanic explosion on Earth!
Although solar flares can be visible in white light, they
are often more readily noticed via their bright X-ray
and ultraviolet emissions. Coronal mass ejections
often accompany solar flares, though scientists are
still trying to determine exactly how the two
phenomena are related. Solar flares burst forth from
the intense magnetic fields in the vicinity of active
regions on the Sun. Solar flares are most common
during times of peak solar activity, the "solar max"
years of the sunspot cycle.
http://www.windows.ucar.edu/tour/link=/
sun/atmosphere/solar_flares.html&edu=high

Coronal Mass Ejection

http://www.windows.ucar.edu/tour/link=/sun/images/aug1980cme_jpg_image.html

Coronal Mass Ejection
"Without warning, the relatively calm solar atmosphere can be torn asunder by
sudden outbursts of a scale unknown on Earth. Catastrophic events of
incredible energy...stretch up to halfway across the visible solar surface,
suddenly and unpredictably open up and expel their contents, defying the Sun's
enormous gravity." (Sun, Earth, and Sky by Kenneth R. Lang)

These catastrophic events that the author is speaking about are coronal mass
ejections (CME's).

Coronal mass ejections are explosions in the Sun's corona that spew out
solar particles. The CME's typically disrupt helmet streamers in the solar
corona. As much as 1x1013 (10 trillion) kilograms of material can be ejected into
the solar wind. Coronal mass ejections propagate out in the solar wind, where
they may encounter the Earth and inﬂuence geomagnetic activity.

CME's are believed to be driven by energy release from the solar magnetic
ﬁeld. How this energy release occurs, and the relationship between different
types of solar activity, is one of the many puzzles facing solar physicists today.
http://www.windows.ucar.edu/tour/link=/sun/cmes.html&edu=high


Magnetic Storms
CME's can seriously disrupt the Earth's environment. Intense radiation from the Sun,
which arrives only 8 minutes after being released, can alter the Earth's outer
atmosphere, disrupting long-distance radio communications and deteriorating satellite
orbits. Very energetic particles pushed along by the shock wave of the CME can
endanger astronauts or fry satellite electronics. These energetic particles arrive at the
Earth (or Moon) about an hour later. The actual coronal mass ejection arrives at the
Earth one to four days after the initial eruption, resulting in strong geomagnetic
storms, aurorae and electrical power blackouts.
"Thus, the Sun's sudden and
unexpected outbursts remain as
unpredictable as most human
passions. They just keep on
happening, and even seem to be
necessary to purge the Sun of pent-
up frustration and to relieve it of
twisted, contorted
magnetism." (Kenneth R. Lang, Sun,
Earth and Sky)
http://www.windows.ucar.edu/tour/
link=/sun/cmes.html&edu=high

http://ess.nrcan.gc.ca/rrnh-rran/proj3_e.php

Solar Wind
The Sun is flinging 1 million tons of
matter out into space every second!
We call this material solar wind. Once
the solar wind is blown into space, the
particles travel at supersonic speeds of
200-800 km/sec! These particles travel
all the way past Pluto and do not slow
down until they reach the termination shock within the heliosphere. The Heliosphere is
the entire region of space influenced by the Sun.

The solar wind plasma is very thin. Near the Earth, the plasma is only about 6 particles
per cubic centimeter. So, even though the wind travels SUPER fast, it wouldn't even
ruffle your hair if you were to stand in it because it's so thin! But, it is responsible for
such unusual things as:

•
auroral lights

•
fueling magnetospheric storms
The particles of the solar wind, and the Sun's magnetic field (IMF) are stuck together,
therefore the solar wind carries the IMF (interplanetary magnetic field) with it into space.
http://www.windows.ucar.edu/tour/link=/sun/solar_wind.html&edu=mid


Aurora

http://www.nasa.gov/centers/goddard/
news/topstory/2005/dueling_auroras.html

http://apod.nasa.gov/apod/ap060329.html


Solar Surface and Atmosphere
LACC: §14.3, 15.2, 15.3
• Know the sun’s atmosphere: photosphere
(visible), chromosphere (reddish), corona (2
million Kelvin), solar wind (e- and p+’s)
• Know solar surface features: granules,
sunspots, prominences, ﬂares, coronal mass
ejections
• Know how the sun affects the earth: CME
disruption of electronics, aurora


HW: Franknoi, Morrison, and Wolff,
Voyages Through the Universe, 3rd ed.

• Ch 14, p354: #5--Prominence, Flare, Coronal
Mass Ejection (mention energy, size, and time)

• Ch 15: Image Analysis Quizzes accessible
from: http://www.brookscole.com/cgi-brookscole/
course_products_bc.pl?

• 16, 17: Tutorial Quizzes accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?

Due beginning of next class period.


A1 15 Our Sun

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A1 15 Our Sun