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The Sun

The Sun. By James Harkin. How do we know what the Sun is made of?.

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The Sun

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  1. The Sun By James Harkin

  2. How do we know what the Sun is made of? We know what the Sun is made of because we know that atoms will absorb very definite wave lengths and therefore very definite colours. When atoms are excited each different type gives off very definite wave lengths and therefore very definite colours; because we know this we know what elements are in the Sun. To see what visible light is emitted and absorbed from atoms we use a spectroscope. If you look at white light through a spectroscope then you will see all of the spectrum with different colours representing different wave lengths. The full spectrum from white light is continuous and has no black lines in it. This is called a continuous spectrum.

  3. How do we know what the Sun is made of? Another type of spectrum is called an emission spectrum. In this type of spectrum you look at an excited element through a spectroscope. When you look through you will see coloured lines on a black background. The coloured lines are the different colours of light that the element gives off, with each colour representing a certain wave length. Here is the emission spectrum for hydrogen with the wave lengths underneath.

  4. How do we know what the Sun is made of? The last type of spectrum is the absorption spectrum. In this spectrum you pass white light through a gas, and when it comes out of the other side if you look at it through a spectroscope you will see a spectrum with black lines in it. Because elements absorb and emit the same wave lengths where the colour was in the emission spectrum there will be black in the absorption spectrum and where there was black in the emission spectrum there will be colour in the absorption spectrum. Here are the emission and absorption spectra for hydrogen (the absorption spectrum is underneath).

  5. How do we know what the Sun is made of? Now if you wanted to you could run a emission or an absorption spectrum on the Sun and because each element gives out a different type of light you could see what elements were in the Sun. Here is an absorption spectrum for the Sun. On it there are thousands of different element absorption lines. The darker and wider the line the more of the element that corresponds to it. For example the darkest widest lines correspond to hydrogen the most common element in the Sun. The second most common element in the sun is helium. In 1870 when an absorption spectrum was run one set of lines in the yellow part didn’t correspond to any known element, so Lockyer the man who had run the test named it Helium after the Greek Sun god Helios. 25 years later Helium was discovered on Earth.

  6. hydrogen helium helium hydrogen

  7. What is the Sun made of? • The Sun, as you know from the previous slide, is at the moment mainly made up of hydrogen with quite a lot of helium. The composition of the Sun is: • 74% hydrogen (the must common element in the universe), • 25% helium, • Carbon, nitrogen and oxygen make up just less than 1%, • The rest is made of many other elements such as neon, iron, silicon, magnesium and sulphur.

  8. Where does the Sun’s energy come from? In the early 19th century some very clever people thought the Sun was powered by coal. The only problem with this was that the Sun would burn itself out in a few thousand years. The Sun actually gets its energy from a process called nuclear fusion. In nuclear fusion nuclei of small atoms fuse together to form larger nuclei but in the Sun’s case hydrogen is converted into helium; this is why the composition of the Sun is always changing. Basically mass is converted into energy. The conversion of hydrogen to helium can only happen under tremendous pressure and heat because the nuclei must hit each other at tremendous speed. The conversion happens in three stages; the first stage is when two hydrogen protons fuse to make heavy hydrogen. Next a heavy hydrogen fuses with a hydrogen proton to make unstable helium. Finally two unstable heliums fuse to form stable helium and two hydrogen protons.

  9. How does nuclear fusion convert energy? The reason why nuclear fusion creates energy is because the mass of the products formed are slightly less than the starting mass. The mass that is not there any more is converted into energy. To work out how much you must understand Einstein's theory E=MC2 (energy=mass times the speed of light times the speed of light). So the average mass lost per second is 4x1011g and the speed of light is 3x108 m/s therefore the power output =4x1011x(3x108)2= 3.6x1028 watts. From working this out we know that the Sun’s energy output which varies by about 0.1% is about 3.6x1028. Also, even though the Sun looses 400,000 tons per second the Sun will keep going for another 5 billion years. Of course people have tried to make energy by nuclear fusion but present day results take up more energy than is made. However, if we could harness the Sun’s power output for 1 second it would keep us going with enough energy for the next million years.

  10. Suns layers! There are 7 layers in the Sun; the core (the centre of the Sun), the radiative envelope, the convective envelope, the sub surface flows, the photosphere, the chromosphere and the corona (the outer atmosphere of the sun). The core is where nuclear fusion takes place and is about 15,000,000° C. The core also has a very high pressure at 250 billion atmospheres; because of the pressure light travels at less than 1 mm per second. This means the heat and light produced in the centre of the sun takes 200,000million years to reach the surface, but just another 8 minutes for it to reach the Earth. The core makes up over half of the Sun’s mass, but occupies less than 2% of its volume.

  11. Solar envelope The Solar envelope is the second most inner layer and is made up of two layers; the radiative envelope and convective envelope. In the radiative envelope it is more efficient for heat and light to travel by radiation so it does. By the time the energy reaches the convective envelope it is more efficient for the energy to travel by convection so it starts to travel in this way. The solar envelope puts pressure on the core and maintains its temperature. The solar envelope contains 49% of the Sun’s mass but 90% of its volume. The solar envelope is about 3900000°C. The heat transfer in the solar envelope.

  12. Photosphere The photosphere is the surface of the Sun and is where the sunlight we see is emitted. The photosphere is a very thin layer and is only about 6000°C but still enough to vaporize solid rock. However, it still bubbles like a giant bowl of porridge with bubbles 1000 miles across. Underneath the surface of the Sun there is a complicated network of subsurface flows.

  13. Sun spots are dark regions on the surface of the Sun about the size of the Earth. They are of course only dark in comparison to the rest of the Sun, but are still bright enough to blind you if you looked at one. The spots are constantly moving. When observed the spots all seem to move in the same direction, this showed the Sun is rotating and other evidence showed it is faster at the equator than the poles. Sun spots come and go in an 11/12 year cycle with sometimes their being no sun spots at solar minimum and sometimes hundreds at solar maximum. Sun spots also have an effect on our climate. For 70 years from 1645-1715 there were no sun spots on the surface of the Sun. Sun spots This picture shows how the Sun changed between 1991 and 1995.

  14. Sun spots also have an effect on our climate. For 70 years from 1645-1715 there were no sun spots on the surface of the Sun. This correlated almost exactly with the last period of prolonged cold to strike the northern hemisphere. This is sometimes referred to as the little ice age. In the little ice age there wasn’t a huge dip in temperatures; just a degree or two but it was enough to have drastic effects. For example the Viking colonies in Greenland were wiped out and the population of Iceland fell by a half. Also the Thames froze over which meant that fairs were held on the ice. The cold wasn’t caused by the solar output lessening, in fact no matter how many sun spots there are the output never changes.

  15. If you look at the sunspots in the uv the sunspots burn a bright white and through x-ray you can see plumes of super heated gas erupting from the sun spots. By placing a disc in front of the sun you can simulate an eclipse. By doing this you will see solar flares and coronal mass ejections which erupt from the heart of sun spots.

  16. The temperature in a solar flare is tens of millions of degrees which means there is a very dramatic change in temperature over a short period of time. When they erupt completely masses the same as Mount Everest are flung out into the solar system.

  17. Because there are fewer sun spots at solar minimum there are therefore fewer flares and at solar maximum there are more sun spots therefore more flares. The cause of these explosions is not fusion but magnetism. The Sun is covered in a complex network of magnetic fields. With the areas with the strongest fields being the places where the Sun spots are. At the sunspots the magnetism can be magnified 10,000 times. The sun spot magnetic fields are between 1000-3000 gauss which is roughly the same as a very strong household magnet. The difference is that the sun spots are much bigger. Sun spots are dark because strong magnetic fields prevent some heat reaching the surface.

  18. The magnetic fields can be seen using special equipment. This shows they can arch 200000km high. If you were to add up the total energy content of one of these loops it adds up to about 1021 joules of energy, which is about 10 times the annual energy consumption of the USA, but there are thousands of these loops. The loops are caused by the twisting of the Sun’s basic magnetic field. This happens because when the Sun rotates faster at the equator than the poles it drags and stretches the fields. As the fields get more and more twisted they break through the surface, until at solar max the whole surface is covered in loops stretched to breaking point.

  19. Solar flares are what happens when the strain gets too much and the loops snap. When the loops snap all the energy stored in the magnetic field is released at once and billions of tons of plasma are fired into space at huge speeds; this is the solar wind. If the plasma is bound for Earth then it will take two days to reach us and when it does the Earth’s magnetic field deflects most of the blow. The auroras (more commonly known as the Northern and Southern lights) are produced when the solar wind gets through the magnetic field at the poles and strikes the upper atmosphere. At Solar max the auroras can be seen as far south as Athens. The buffeting of the magnetic field causes migratory animals that navigate using the magnetic field to lose their bearings and fly or swim to the wrong place. The disrupted magnetic fields can affect electronics and sometimes the solar wind can even destroy satellites.

  20. Graph and global warming As you can see from the graph there is a strong correlation between sun spot numbers and the Earth’s surface temperature. However in recent years when the temperature should have been falling with the sun spot numbers it has increased. This increase has correlated with a recent surge in carbon dioxide levels. However Carbon dioxide has only been recorded accurately since 1958 so we can’t be sure whether this is the cause.

  21. The atmosphere The inner atmosphere is called the chromosphere and is a red circle around the outside of the Sun. The chromosphere is red because of an abundance of hydrogen. Also strangely the temperature of the chromosphere is higher than the photosphere ranging from 6000°C to 50000°C. The outer atmosphere is the corona. The corona is hotter still ranging from 1000000°C to 2800000°C.The corona is only visible during eclipses and is made of a low density cloud of plasma which extends millions of kilometers into space.

  22. Life cycle of the sun The universe started by with the big bang and has been expanding at the speed of light ever since. The Sun however was born in a nebulae. Nebulae are huge clouds of hydrogen which can be hundreds of light years across. They are some of the brightest parts of the sky due to the intense light of newly formed massive stars. The Sun’s life started in a cold, dark cloud of gas which was very stable. These clouds can stay stable for thousands of millions of years before they do anything by being hit on one side by a supernova blast wave.

  23. A supernova blast wave is produced from a massive star exploding at the end of its life. A supernova blast wave is a very energetic compression wave, so when it hits the cold, dark gas cloud it compresses it. The shock waves knock the cloud off balance which causes localised clumps of hydrogen to form. The clumps of hydrogen are what new stars grow from and the increased gravity of the clumps causes them to pull together. This part of the process lasts for millions of years and as more hydrogen is squeezed into the clumps the pressure and temperature increases. As they get bigger and bigger they start to spin. This throws out a disk of debris that will in time form a solar system. This is the reason why the planets all rotate in the same direction around the Sun and that they are on the same flat sheet.

  24. Finally the star lights up and because it produces so much energy in the first fusion the process takes off. The star then begins its lifelong activity of making other elements. Every atom in the universe was made in a star, therefore every element was made from hydrogen. In about 5 million years the Sun will run out of hydrogen. When it does it will become a red giant. The core will shrink because of lack of fuel. This will generate so much heat that the outer layers will expand into the solar system meaning the inner planets will be swept up; it may even swallow up the Earth. The Earth is doomed anyway because the Sun will burn 2000 times hotter than it is now and will melt and seal the outer layers of the planet. When the Sun finally stops burning its core will collapse and finally it will blow its last shroud of gas into space. How big the Sun will become as a red giant.

  25. How large is the Sun compared to other stars? The Sun is huge (you could fit the Earth in it 1000000 times) but the Sun is just an average star with many stars being much bigger than it. These pictures show how big the Sun is compared to other stars. The brightest star in the sky The sun 1 pixel

  26. Sites I have used • The sun websites: • http://intro.chem.okstate.edu/1314F00/Lecture/Chapter7/Lec11300.html • http://www.efg2.com/Lab/ScienceAndEngineering/Spectra.htm • http://www.astronomygcse.co.uk/AstroGCSE/Unit2/Unit2MoonandSun.htm • http://staff.imsa.edu/science/astro/astrometry/spectra/sld010.htm • http://www.solarnavigator.net/the_sun.htm • http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/suncomp.shtml • http://fusedweb.llnl.gov/CPEP/Chart_Pages/5.Plasmas/SunLayers.html • http://www.co-intelligence.org/newsletter/comparisons.html • http://www.sciencedaily.com/releases/2007/04/070416152726.htm • http://www.northern-lights.no/english/contest/winner.shtml • http://sunearth.gsfc.nasa.gov/sunearthday/media_viewer/flash.html • http://solar.physics.montana.edu/YPOP/Spotlight/Tour/tour07.html • http://en.wikipedia.org/wiki/Image:Solar-filament.gif • http://www-istp.gsfc.nasa.gov/Education/wcorona.html • http://www.outdoorsearch.co.za/images/Uploads/200610128237nebulae3.jpg • http://www.solarviews.com/browse/ds/cloop.jpg • http://www.lcsd.gov.hk/CE/Museum/Space/EducationResource/Universe/framed_e/lecture/ch15/ch15_cnt.html • http://www.brighton73.freeserve.co.uk/gw/solar/temp_vs_spot_irradiance.gif

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