Astronomy: The Sun

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Above is an image of the different layers of the Sun.

Table of Contents

  1. General Facts
  2. Layers of the Sun
  3. Surface Phenomenona
  4. For Educators

General Facts

The Sun is an above average sized star that holds our solar system in place. It is in the top ten percent, in terms of size, of all stars as most stars are red dwarves. A star is a ball of plasma(super-heated gas) that releases energy in the form of heat and light due to the fusion of gases(this is called fusion, it’s when atoms combine to form heavier ones due to the energy in the surroundings). Even though our Sun is 99% of the mass of the solar system, there are stars that are a thousand times larger(the star Betelgeuse is 700 times larger than our sun). The mass of our sun is what holds our solar system in an elliptical orbit, masses exert a force on each other called gravity(insert link to gravity post here). We do not know much about gravity but the link will lead to a post about what we believe happens.

Layers of the Sun

Just like Earth has different layers(Core, Mantle, Crust), the Sun has different layers. The innermost layer of the sun is the core. The pressure in the core of the sun is 260 billion atm(1 atmosphere, or atm, is the air pressure at sea level on Earth) and 15 million Kelvin(at this large scale, 1 Kelvin is approximately 1 Celsius). This is the layer where most of the hydrogen fusion happens, because the pressure(and thus energy) is immense. Every second the sun converts 700 million tons of hydrogen, forming 695 million tons of helium and 5 million tons of energy. To convert it, this is where Einstein’s classic E=mc^2, so 5 million tons of energy is 4,535,923,700kg(5 million tons as kg)*(3*10^8)^2=124,827,108,157,891,338,889 Watt*hours(so this number is the number of joules of energy expended in an hour, and it is gigantic) . For reference, your powerful home lightbulb is 100 Watts, so yes, the Sun produces a crazy amount of energy.

Above the core is the convective layer, this is where all the hydrogen moves up to because it is less dense than helium. This is called convective layer because the temperature gradient between this layer and the core causes the hydrogen to become less dense, float up, cool down, and then sink again.

The circles in the convection zone are the cycle of hydrogen atoms. The image was retrieved from http://burro.case.edu/Academics/Astr221/StarPhys/opacity.html

Above this is the photosphere, which is thin enough for the light to escape. The top layer is the corona, which is thinner than the photosphere but much hotter than it. The corona stretches for many million kilometers. The solar wind is over a million km/hr

Surface Phenomenon

The first important thing to know about the surface of the Sun is that light is emitted from it. This light is what we see. You have heard that it takes 8 minutes for light to be made from the Sun and seen by us. This is only partly true. The distance from the Earth to the Sun is such that it takes 8 minutes for the light to reach us(the speed of light is 3*10^8 meters/second so multiply that by 480 seconds to get the total distance from Earth to Sun). However, the light we see is often more than 100 million years old! This is because of the fact that fusion, where light is produced, occurs in the core. So this light has to escape to the photosphere where it has some potential to escape. While in the core, it will just be circulated for many millions of years until it may escape.

That is how light comes to us, but there are a lot of cool phenomena that happen on the Sun also. These are invoked by the Sun having a significant magnetic field. This magnetic field is induced by a flow of electric charge in the Sun(a current can create a magnetic field, this is Ampere’s law). The flow of charge occurs in the convection zone, because of the high temperatures, not just hydrogen atoms but also free electrons get circulated. Related fact: The earth has a magnetic field for the same reason, but it is because of liquid metals flowing in the outer core that causes a flow of charge. This magnetic field on the sun causes many interesting phenomena on the sun.

Sun Spots

Sunspots are formed when the magnetic field doesn’t allow the plasma to return down the convective layer, causing it to dim on the surface. These sunspots appear in pairs(imagine a North pole and south pole of a magnet, sunspots occur in such a fashion often).
Faculae are the bright rings around the sunspots formed by the concentrated magnetic field. These are very bright due to the heavy magnetic field causing significant circulation.

Solar Flares

A solar flare is when the magnetic field snaps, ejecting material into space. These often occur around sunspots because, as we discussed, the magnetic field around the sunspots is extremely prominent. A solar flare is like a slingshot of solar mass(the components of the Sun) being shot. When you hear of the risk of the Sun eliminating radio communications, flares are the reason

Solar Prominence

A solar prominence is when the sun’s magnetic field pushes the plasma out toward the surface. The difference between a flare and prominence is that a prominence does not eject anything. Rather, a large ring of plasma is formed on the surface of the Sun, directed by the magnetic field.

Coronal Mass Ejections

Coronal mass Ejections(or CMEs) is similar to a flare except its stronger and covers a wider area. These often occur when a solar prominence snaps, because the prominence holds a lot of energy it ejects much more mass. A CME in 1989 caused a total power outage in Quebec. In 2012, another CME occurred but in a different direction, saving the Earth from huge damage. These caused concern because the Earth’s atmosphere protects us from solar emissions, but a CME is so powerful that it gets free electrons through our atmosphere and can cause damage to a lot of our technology.

For Educators

After doing a short presentation about the concepts in the post, I would recommend doing a demonstration on the concept of convection. Check out this you tube video if you need inspiration for how to set one up(or would like to show it yourself). Teaching about the Sun is easiest using diagrams, so I would recommending making diagrams for the different layers of the Sun. Finally, teach about the phenomena by explaining their impact, like the examples I gave in the CME section. This is so students understand that the Sun is more than what we think of it, and that there is a lot to learn about it.

Thank you!

Thank you for reading about the Sun! If you have any comments, let me know at vijaypbharti01@gmail.com or in the comment section below.