TODAYS TOPIC- INNER AND OUTER LAYERS OF THE SUN I used to work at the local Dairy Queen when I was 14 years old…(before child labor laws were taken seriously in the South). It was 1979 and I was making a whopping $1.37/hour. I worked about 80-100 hours a week and I was the richest kid on the block! Of course, I was there from about 20 minutes after school until closing everyday and all day weekends so I didn’t have any time to spend my money. When I worked there I created a special treat for me and my friends which consisted of a core of hot fudge surrounded by peanuts, hot fudge, ice cream, strawberries, peanuts, hot fudge and a layer of chocolate dipped cone coating. I froze all of this in the back freezer and would treat myself to one every now and then. I called it “The Nutty Mudball”. I had no idea how close I was to planetary geology back in those days ☺ and it has always fascinated me to see the various layers inside of the stuff in our Universe. The Sun is no exception. It is an intricate layercake of interesting stuff and it all combines to make our world livable, warm and bright. The Sun (as covered in a previous topic) was formed from a nebulous cloud of scattered atoms and molecules about 5 billion years ago. It took millions of years after the initial nuclear fusion chain reaction started in the core for it to get itself “together” into the stable structure that we enjoy today. The core of the Sun is simply the actual area in which it has become hot enough due to the force of gravitational compression to maintain the proton-proton cycle of nuclear fusion. The Sun’s core is about 25% of its total diameter of 875,000 miles. The core of the Sun is a place that would be completely foreign to us as it is more dense than rock but it is completely made of plasma (superheated gas). It is not a solid, yet if you could stand the heat you could stand on it. Very strange indeed. There is almost nothing on this planet that would not be immediately vaporized by the temperatures of 27 million deg F in the core of the Sun. The layer around the core is called the “radiative” zone and it is just that. It is an area where photons carry away the energy and heat from the core in a basically straight outward motion of crashing into Hydrogen atoms, and being absorbed and re-emitted outwards. There is a line called the “tachocline” that separates the inner core and radiative zone from the next layer which is called the “convection” zone. The rotational speed and direction of the Sun changes significantly at the tachocline causing the convection zone to produce a rolling motion exactly the same as the boiling water on your stove when your making pasta! This swirling motion conveys the energy from the inner Sun to the photosphere and is responsible for the little bubbles of energy that cover the Sun’s visible light surface. We call them granules because….they look like little salt granules in still images! These granules constantly boil up, release their energy, and then fall back down in the space of just a few minutes and can be as large as the continental US! By the way, this difference in the rotational characteristics between the various zones is directly responsible for the intricately twisted magnetic field lines which cause all of the observable phenomena on the Sun that we all love to take pictures of. Thanks Electromagnetism! The outer layers of our magnificent star begin with the photosphere where sunspots and granulation are seen. Photosphere means “light” sphere and this is where all the visible light is released from the Sun into its atmosphere and the solar wind. Next up in altitude is the Chromosphere where the energy is manifested by magnetic field lines exiting and entering the Sun’s surface. This topic is covered in a previous post. The Chromosphere is where all the action occurs in the images frequently posted on this forum by users of narrowband Hydrogen-Alpha and Calcium K line telescopes. There is then a layer called the transition zone just above the chromosphere. This is largely not understood by solar physicists as of today. For some reason, the temperature of the plasma rises sharply back up into the millions of degrees in this region and is expelled into the Sun’s Corona and solar wind. Electromagnetism is , of course, the key but we are still studying this mysterious level of the Sun. The Sun’s Corona is the gigantic, always fluctuating, area of the outer atmosphere of the Sun that is seen in eclipse photos. The Sun’s Corona is much hotter than the photosphere and it is very unstable. During solar maximums, like we are in now, the Sun can expel an entire half of its Corona out into space due to magnetic instability. The last part of the Sun’s realm is the Solar Wind, which radiates in every direction away from the Sun and influences every object in our solar system from planets and Moons to Comets in the Ort cloud. I love to quote the sizes of things Sun related and the Sun’s solar wind which is bounded on one side only by the heliopause and terminal shock as it travels through the interstellar of the galaxy, is around 94 AU, (8,742,000,000 miles) away from the Sun. The voyager probes launched in the 70’s are now in this area of our solar system. Running the faucet in your sink can easily represent this system! The image attached below shows the termination shock of a stream of water, which is pretty close to the same movements as the Sun’s outermost influence. By the way, this distance may seem unimaginably large, but it is really quite insignificant in astronomical terms. 94 AU is about .001 light years. That is JUST ONE LIGHT YEAR is 63,241 AU’s. The nearest star is 4.2 light years away….so, you could fit 2,825 entire Sun’s and their outer reaches between here and the next star. Oh yeah, and there are over 200 billion stars in our galaxy. ☺ Feeling small? Don’t worry, there is just as much stuff smaller than us as there is larger. I like to think we are in the middle…☺ Thanks for reading.
Posted on: Thu, 08 Aug 2013 13:49:34 +0000
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