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

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 or in the comment section below.

Astronomy: Our Solar System

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Table of Contents

  1. Introduction/The Sun
  2. Inner Planets
  3. Asteroid Belt
  4. Outer Planets
  5. Kuiper Belt
  6. Oort Cloud
  7. For Educators
Embed from Getty Images

Now that we know of the moon and Earth, we will be diving into the planets. This post will be an overall description of what we call our solar system, which is everything that orbits the Sun. This orbit is caused by the gravitational pull of the Sun. I won’t describe how that works currently but if I do, I will replace this line with a link to the blog post explaining what is known as Newton’s Law of Gravity and Kepler’s Laws(these help us describe planetary motion).

For now, lets talk about the solar system. It starts with our Sun, which is a very large(2*10^30 kg and radius of 700,000 km) “ball” of mainly hydrogen plasma(superheated gas for our purposes). The sun is 1 Astronomical Unit, or AU, from us(Earth), which is equal to about 93 million miles. The important thing is that the Sun releases a lot of energy in the forms of light and charged particles, which account for us having heat and many other interesting phenomena. Also, the Sun is what holds everything together, because the Sun is 99.8 percent of the total mass of the Solar System(Jupiter is literally insignificant in mass to the Sun).

The Terrestrial(Inner) Planets

Next we have the four terrestrial planets, which are, in order of increasing distance from the Sun, Mercury, Venus, Earth, and Mars. These are called the terrestrial planets for two reasons, one, they are primarily rock and do not have much of a gaseous component(less atmosphere) and they are separated from the rest of the planets by the Asteroid Belt. The term terrestrial is used to say that each of these planets are like Earth. They all have rocky cores made of iron and nickel.

Asteroid Belt

The Asteroid Belt is composed of small rocks that could not aggregate together like moons and planets do. These small rocks are asteroids(I say small but the smallest asteroids are more than a half mile across). They separate Mars and Jupiter. This belt is huge, but most of the mass is aggregated into 4 large asteroids, the largest being called Ceres. This asteroid is considered a dwarf planet and is 500 kilometers in radius(The Earth is 6400 kilometers for reference). The asteroids are very sparse, meaning most of the belt is empty space. Finally, these asteroids are also called planetesimals because they are considered the pre-requisites to the formation of a planet.

Jovian Planets

Pass the asteroid belt to find Jupiter, the first of four Jovian Planets. Jovian means “Jupiter-like”, so all of these planets are like Jupiter. The planets after Jupiter are Saturn, Uranus, and Neptune. These planets are gas giants, because they are much larger than the terrestrial planets and are mostly gaseous. Note that these planets are much farther away from the Sun than you might think, the distance between planets is not proportional. From Earth to the Sun, as we said, is 93 million miles, while Jupiter to the Sun is 500 million and Uranus is 1.8 billion miles away from the Sun. Jupiter is the largest, Saturn has the rings that you probably know about, and Uranus and Neptune are very similar, the biggest difference being how far from the Sun they are(Neptune’s year is double that of Uranus’s approximately).

Kuiper Belt

Beyond the Jovian Planets lies the Kuiper Belt. This begins around 50 AU(astronomical units/ 1 AU= distance from Earth to Sun) beyond the Sun. The belt is very similar to the asteroid belt, except you will find more comets and ice rocks because of the extremely cold temperatures. This belt is also very sparse in rock density(mostly empty space), but is also much larger than the Asteroid belt.

Oort Cloud

Finally, let’s discuss what is known as the Oort Cloud. This is just barely part of the Solar System, it is 2,000 AU away from the Sun(remember the Kuiper Belt is only 50 AU). This ‘cloud’ is believed to be a large sphere of sparsely populated ice rocks. However, sparsely populated does not mean underpopulated. It is believed to have trillions of different objects. Because of how far away it is, this cloud is just speculative and we do not know if anything really exists there except for very long period(time per revolution around the Sun) comets.

For Educators

After doing the five minute presentation on the subject(make it however you feel like, just stay away from talking too much, visuals and audio are more useful). Afterwards, you have a couple of main goals.

  1. Explain how the composition of the gas giants and terrestrial planets differ
  2. Get relative distances between the planets

For goal 1, the easiest way is to explain gas giants as being like cotton candy(you could fill a bag with cotton candy to make it round like a planet). Since they are gaseous, they do not have much solid like behavior and will be fluid(this is much less dense than the actual densities of Jovian Planets, but will convey the point). Note, however, since they are so massive, they will make you feel heavier on these planets(gravity is more than here on Earth.) For terrestrial planets, you could use a rock because these terrestrial planets are very dense(mostly rock). Make the rock round to reflect a planet. Even better is have the students make these planets from some materials and paint them(you could use something like Styrofoam for the Jovian Planets and actual rocks for the terrestrial planets). Please remember that for Jovian Planets are much denser than Styrofoam or cotton candy, I am just using those to convey the “texture” of the planets in a easy to understand way. Most of the density would come from the mass of the Planets packing the gases in the core to make it solid.

For goal two, I am using a very easy to understand description from NASA. ” One way to help visualize the relative distances in the solar system is to imagine a model in which the solar system is reduced in size by a factor of a billion (109). The Earth is then about 1.3 cm in diameter (the size of a grape). The Moon orbits about a foot away. The Sun is 1.5 meters in diameter (about the height of a man) and 150 meters (about a city block) from the Earth. Jupiter is 15 cm in diameter (the size of a large grapefruit) and 5 blocks away from the Sun. Saturn (the size of an orange) is 10 blocks away; Uranus and Neptune (lemons) are 20 and 30 blocks away. A human on this scale is the size of an atom; the nearest star would be over 40,000 km away! “(See the link below for the source). ” What they are saying here is that if you scaled everything down to a very small size, you could use these numbers to explain the relative sizes and distances of the planets. Students do not need to remember any numbers, rather they should get the concept that things are not proportional. I would recommend taking students on a walk for things like the distance to Jovian Planets since they are quite large.


Thank you

Thank you for reading! Any questions or comments, let me know at