Solar System

The Galaxies, The Stars and The Sun

By Madison Nef

The Sun

The sun is the largest star in the galaxy that is currently known. It is in the center of the Solar System, and all planets in our Solar System revolve around it. Compared to the planets, the sun is extremely large- to the point that it takes up 99.86% of the system’s mass. The sun is 865,000 miles wide, which makes it 110 times wider than the Earth… and Earth isn’t even the largest planet! No wonder. 74% of the sun’s mass is hydrogen. Helium makes up roughly 24%, and a combination of the heavier elements (oxygen, carbon, iron and neon) make up the remaining percentages.

The sun is also extremely hot, if you were stupid enough to not know. However, I bet you didn’t know EXACTLY how hot it is! It’s 5,500 degrees Celsius on the surface, with its core being a whopping 13,600,000 degrees Celsius!   

It also generates a large amount of energy by combining large amounts of hydrogen nuclei into helium. This is called nuclear fusion… also; because of the sun’s huge impact on the Earth, many ancient cultures thought or portrayed the sun as a deity or a god. Some famous examples of this are Ra, the Egyptian sun god and Tonatiuh, the Aztec sun god.

The Stars

What even is a star? Do you ever wonder this..? I do. A star is actually a large sphere of hot gas, known as plasma, that is being held together by its own gravity. Stars radiate energy created by nuclear fusion, much like a smaller-scale version of the sun (since the sun is just a gigantic star). This creates helium. As a star begins to die (yes, they die), it changes the helium slowly into heavier chemical elements like carbon and oxygen. When this happens, the star changes drastically in color, density and size, resulting in its death.

The sun is closest to the Earth, and is known as a “G2 yellow dwarf star”. Boy, if they think the sun is a dwarf star… I’d hate to see what they mean by a big star! Anyway, besides the sun, the nearest star to Earth is Proxima Centauri. It’s 4.2 light years away… meaning that light from that star would take 4.2 years to reach Earth from where it is located. Even using the fastest and most efficient technology known today, it would take roughly 75 thousand years to get there.

Each galaxy contains hundreds of billions of stars… and there are estimated to be hundreds of billions of GALAXIES. Agh, inception! In the Milky Way alone, there are well over 400 billion stars… and that’s what we KNOW of. In the entire universe, there is estimated to be about somewhere from 70-300 sextillion stars. Most of these stars have lifespans of 1-10 billion years; depending… and some appear to be the age of the Universe (observed) itself- 13.8 billion years old.

The Galaxies

Let’s finish up with galaxies- a galaxy is a large group of stars, star clusters, gas and dust that is all held together by gravity. The only thing that separates galaxies from being one gigantic star is the dark matter that is also mixed it. The word is derived from the Greek word for ‘milky’; which is thought to be a reference to the Milky Way.

Most galaxies are gigantic, and average size is somewhere between 10 million (which is considered small) and 100 trillion (which is considered large). There are an estimated 170 billion+ galaxies in our universe- putting the number of stars at over 100 sextillion.

While galaxies are quite similar in many ways, there ARE some variations. There are many different shaped galaxies, the two most popular and most prominent being elliptical and spiral.

Elliptical galaxies are shaped like a disk, and because of this are typically larger and are usually very old. They also have less gas and dust, lowering the creation rate of new stars within them.

Spiral galaxies are stereotypical galaxies- rotating flattened disks with at least two spirals of new stars roping out from the center hold of older stars. The heavy molecular clouds of hydrogen allow a LOT of star formation… hence their often large and never-ending appearance.

Well- that’s about it! I hoped you learned something about our Solar System- I know I did.

~Maddie