Transcript Different wavelengths…

The Sun
Link to opening video
Stellar Fusion
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Where does the sun get its energy?
The process of nuclear fusion in which particles in
the nucleus of the atom combine to form larger
nuclei.
This larger nucleus has a slightly smaller mass
than the nuclei that combined to make it.
The missing mass has been converted to energy.
The sun is made mostly of hydrogen which has
been fusing to helium for about 5 billion years,
and will continue to do so for about 5 billion
more.
Fusion link
Stellar Composition
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So, the sun is mostly
hydrogen, with a lot of
helium, with very small
amounts of other material.
Where did this other
material come from?
In the 1st part of the
introductory video they
told us that it came from
the explosion of earlier
stars. We discussed this
when we learned about
other stars.
Element
Percentage Comp.
Hydrogen
73.5
Helium
24.8
Carbon
0.33
Nitrogen
0.12
Oxygen
0.79
all other elements
0.46
E = mc2
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The amount of energy created in this process can
be calculated by the famous equation above. What
does it mean?
 Matter is changed into energy during fusion
 The amount of energy created when you change
matter to energy is equal to the mass of the matter
converted times the speed of light constant c
squared (a very large number), so E = mc2
 This is a lot of energy for a small amount of
matter, and billions of reactions occur every
second in stars, producing great amounts of energy
Energy from matter
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Whenever matter is destroyed, energy is created.
For example, when you light a match, the combustible
material contains potential energy as matter. During the
reaction this material changes mostly to other matter, but
a little changes to energy, in the form of heat and light.
 This is just like the food you eat which is stored solar
energy. This is chemically changed to energy to fuel your
body.
 Chemical reactions like these create energy - but only
small amounts compared to the amount created from
nuclear reactions - like fusion in stars.
Fusion vs fission
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Both fusion and fission can create energy from
matter, as long as the process gives out more energy
than it takes to make it occur
Fission is the process of splitting a nucleus
In natural fission, the energy required to split the
nucleus is less than what is obtained when it splits.
Again, in fission, there would be less mass after the
reaction since matter is transformed into energy.
Thus the law of conservation of energy and matter is
followed.
How can both fusion and fission generate energy by
transforming matter to energy? This involves what is
called binding energy. We discussed this briefly
when we discussed the evolution of stars.
The Sun, a
complicated
place
The sun’s layers
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Core – where fusion
takes place
Radiation zone
Convection zone
Photosphere – the
“surface” of the sun
Chromosphere – the
red color layer
Corona – the sun’s
crown
Energy is created by fusion reactions in the
core. This energy migrates to the surface.
A closer look at the sun link
The Sun in 4 Wavelengths
Continuum
Hα
30.4 nm
Soft x-rays
We can learn a lot about the sun by observing
it with different instruments that can “look” at
different wavelengths of light.
The Sun in 4 more
Wavelengths
Link from classzone
17.1 nm
1038 nm
28.4 nm
393.4 nm
(Ca K)
Different wavelengths
show different solar layers
Links:
H sunspots
80 K He
1.6 M Iron UV and
Flaring region UV
iron
2 M X rays
Magnetic and
corona split
Spots to UV
Different wavelengths…
Different heights…
Composite of eight images taken at
different wavelengths
Active
regions in
different
wavelengths
Trace video link
Spectra – Bar Code of the
Sun & Stars
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A hot object emits light with many
wavelengths and a certain shape
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If this light passes through a gas, the atoms
and molecules of the gas will be absorbed at
specific wavelengths.
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The details of these dark absorption lines
provide information on the gas.
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There is more on this in the spectra
presentation
The Visible Solar Spectrum
Solar Atmospheric Chemical Composition
The McMath-Pierce
Solar Telescope
Observing in the McMath-Pierce
with Dr. Steven Howell, astronomer
Ms Starkins
The Earth’s Magnetosphere
Magnetic Fields
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Both the sun and earth have magnetic fields. Do you remember
what causes magnetic fields?
 Moving charged particles generate magnetic and electric fields.
Electromagnetic radiation consists of moving electric &
magnetic fields.
 We know that swirling liquid iron in the outer core causes the
earth’s dynamic magnetic field.
 What causes the sun’s magnetic field?
 The hydrogen atoms in the sun are actually ions (charged
nuclei), in which the electrons are removed from the atoms
because of the high temperature of the sun.
 As these ions move, they generate electric and magnetic fields
– these moving fields are the light we see, as well as the other
electromagnetic radiation (like x-rays, UV, etc.) generated by
the sun
Galileo
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Galileo was among the 1st (if not the 1st) to use the
newly invented telescope and observe spots on the
rotating sun.
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We have Galileo’s drawings of his sunspot
observations. This Link animates them in order
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These showed the rotation of the sun.
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Since the sun is gaseous, the rotation varies from
poles to equator. The rotation is faster at the equator.
This causes shearing which twists the magnetic field
lines and produces small local magnetic fields.
Both magnetic fields
Twisted magnetic field lines
created by sun’s rotation cause
sunspots and solar flare activity.
The earth’s magnetic field
is distorted by charged
particles from the solar
wind and flare activity.
A magnetogram
A magnetic field
picture of the sun
showing the
localized
magnetic fields.
Polarity of fields
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Magnets, as you know, have two poles, a North
and a South pole
The magnetic field flows between these two poles
Notice the field lines of the Earth’s magnetic field
on the next slide
You should be able to see these loops that go
between the north and south pole
The field deflects charged particles and the loops
trap charged particles
Magnetic Fields,Sunspots &
Magnetic Loops
Magnetic
Fields 
lines that
connect
north and
south
polarities
Magnetic
Loops 
trapped,
hot
gases
Fly through the loops
…as
seen in
X-ray
SUNSPOTS
Remember that heat migrates upward from the core through
the convection and radiation zones. Sunspots occur where
magnetic fields prevent rising of heated material. Therefore
this spot is cooler than the surrounding sun. A sunspot has
a temperature of about 1500 degrees less than the
surrounding photosphere.
Although
these
sunspots
look dark,
they would
be brighter
than a full
moon if
viewed
separately
from the
sun.
Backed by
the hotter
sun, they
appear
black.
Sunspot link
Material flows around sunspots
Notice that sunspots are commonly as large as, or larger than, the whole earth.
Magnetic fields cause interesting
structures on the sun
Like Prominences
Prominence link
And they can erupt in solar flares
link
Storms on the Sun
Movie
And eject material towards Earth
CME to earth link
Which impacts technology
And causes auroras
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Aurora video
 At both poles usually
 Sometimes far south with major solar
activity
 Classzone pictures
Images of flares,
CME’s
Link
Link 2
Link 3 combined
to see sun and
corona
A coronagraph uses a telescope
with a piece blocking the sun, so
that the corona can be observed at
any time. In effect, it makes an
artificial eclipse.
The Solar Wind
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Of course there is
always some material
streaming out through
holes in the corona.
 This steady flow of
particles is called the
solar wind
Magnetic fields rise and fall in cycles. The number of
sunspots shows this. It increases to a maximum number
about every 11 years.
11 year sunspot/activity cycle
It is actually a 22 year cycle.
For the first 11 years the fields
point in one direction. Then for
the next 11 years they go the
opposite direction.
This is similar to the changes in
magnetic field directions on the
earth, but happens more
quickly and is apparently more
consistent.
Of course, this is only based on
what we have observed over a
relatively short period of time.
The 11-year activity cycle
Link showing cycle changes 91 to 01
Link showing comparison from 96 to 99
Effects of Solar cycles
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Does this affect the earth?
There is evidence to show
that long periods of low
sunspot activity correspond
to cooler periods on the earth.
 For example, the Maunder
Minimum from 1645 – 1716
had very low sunspot activity
and corresponded with a cold
episode called the “Little Ice
Age.”
Classzone.com sunspot activity
And worksheet
What does the sun look like
today?
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Where are we in the solar cycle?
If you were carefully looking at
the graphs and pictures before,
you probably know. Let’s see if
you are right.
 SOHO website
(If this isn’t working, the Space
Weather site below can also help
you.)
 Space Weather site for solar
storms, aurora forec.asts and
other items
What is This?
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sun videos\transit_label_large.mov
 Cool images from STEREO website
How did the sun begin and how
will it end?
Link 1 – formation of sun
 Link 2 – death of sun 1
 Link 3 – death of sun 2
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