The SunThe Sun

Link to opening video

Stellar FusionStellar Fusion 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 CompositionStellar Composition

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 = mcE = mc22

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 matterEnergy from matter 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 fissionFusion vs fission 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.

TheThe Sun, a Sun, a complicated complicated

placeplace

TheThe Sun, a Sun, a complicated complicated

placeplace

The sun’s layersThe sun’s layers 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

A closer look at the sun linkEnergy is created by fusion reactions in the core. This energy migrates to the surface.

The Sun in 4 WavelengthsThe Sun in 4 Wavelengths

Continuum

30.4 nm Soft x-rays

H α

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 The Sun in 4 more WavelengthsWavelengths

Link from Link from classzoneclasszone

17.1 nm

393.4 nm (Ca K)

1038 nm

28.4 nm

Different wavelengths Different wavelengths show different solar layersshow 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 heights…Different wavelengths…

Composite of eight images taken at different wavelengths

Active Active regions in regions in different different

wavelengthswavelengths

Trace video link

Spectra – Bar Code of the Spectra – Bar Code of the Sun & StarsSun & Stars

A hot object emits light with many wavelengths and a certain shape

If this light passes through a gas, the atoms and molecules of the gas will be absorbed at specific wavelengths.

The details of these dark absorption lines provide information on the gas.

There is more on this in the spectra presentation

The Visible Solar SpectrumThe Visible Solar Spectrum

Solar Atmospheric Chemical CompositionSolar Atmospheric Chemical Composition

The McMath-Pierce The McMath-Pierce Solar TelescopeSolar Telescope

 

 

Observing in the McMath-Pierce Observing in the McMath-Pierce with Dr. Steven Howell, astronomerwith Dr. Steven Howell, astronomer

Ms Starkins

The Earth’s MagnetosphereThe Earth’s Magnetosphere

Magnetic Fields Magnetic Fields 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

GalileoGalileo Galileo was among the 1st (if not the 1st) to use the

newly invented telescope and observe spots on the rotating sun.

We have Galileo’s drawings of his sunspot observations. This Link animates them in order

These showed the rotation of the sun.

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 fieldsBoth magnetic fields

The earth’s magnetic field is distorted by charged particles from the solar wind and flare activity.

Twisted magnetic field lines created by sun’s rotation cause sunspots and solar flare activity.

A magnetogram A magnetogram

A magnetic field picture of the sun showing the localized magnetic fields.

Polarity of fieldsPolarity of fields

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 Fields,Sunspots & Magnetic LoopsMagnetic Loops

Magnetic Loops trapped, hot gases

…as seen in X-ray

Magnetic Fields lines that connect north and south polarities

Fly through the loops

SUNSPOTS

Remember that heat migrates upward from the core through Remember that heat migrates upward from the core through the convection and radiation zones. Sunspots occur where the convection and radiation zones. Sunspots occur where magnetic fields prevent rising of heated material. Therefore magnetic fields prevent rising of heated material. Therefore this spot is cooler than the surrounding sun. A sunspot has this spot is cooler than the surrounding sun. A sunspot has

a temperature of about 1500 degrees less than the a temperature of about 1500 degrees less than the surrounding photosphere.surrounding photosphere.

Sunspot link

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.

Material flows around sunspotsMaterial flows around sunspots

Notice that sunspots are commonly as large as, or larger than, the whole earth.

Magnetic fields cause interesting Magnetic fields cause interesting structures on the sunstructures on the sun

Like ProminencesLike Prominences

Prominence link

And they can erupt in solar flares And they can erupt in solar flares linklink

Movie

Storms on the SunStorms on the Sun

And eject material towards EarthAnd eject material towards Earth

CME to earth link

Which impacts technologyWhich impacts technology

And causes aurorasAnd causes aurorasAurora video At both poles usuallySometimes far south with major solar activit

yClasszone 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 WindThe Solar Wind

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 Magnetic fields rise and fall in cycles. The number of sunspots shows this. It increases to a maximum number sunspots shows this. It increases to a maximum number

about every 11 years.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 cycleThe 11-year activity cycle

Link showing cycle changes 91 to 01

Link showing comparison from 96 to 99

Effects of Solar cyclesEffects of Solar cycles 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 What does the sun look like today?today?

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?What is This?

sun videos\transit_label_large.movCool images from STEREO website

How did the sun begin and how How did the sun begin and how will it end?will it end?

Link 1 – formation of sunLink 2 – death of sun 1Link 3 – death of sun 2