Ever wondered about the universe? Well we actually had a whole unit on it, mostly about stars so that's what the first section of this page is on. How they from where and what happens after they do. Next we covered this fancy diagram that helps organize compare and classify stars so if you want to know about that it's in the middle section. Finally we covered galaxies, what they are the different types and what the types show. Learning this is so important because it teachs us about where we are in the world and what we are in.
Stars are all formed for the same thing nebulas (giant clouds of dust and gas) then gravity over time will start to pull it together, and atoms start stick together and forming new elements usually hydrogen into helium. This is called fusion and is where stars get their energy from. If there is more gravity pulling together then the more fusion will happen in a shorter amount of time making a star very big, very bright and most importantly have far more mass, these are called massive stars. Stars that have a normal level of fusion are called average stars, both take different paths. Normal stars like our star follow the path from a nebula, to an average star, to a red giant, to a planetary nebula, to a white dwarf, that fades that to a black dwarf. A red giant occurs when all the hydrogen has turned into helium and helium stars turning into other elements this causes a star to swell up and its color changes to red. A planetary nebula is the scattering of dust and gas that are the outer layers of a star that is dying. Then finally when all the layers float away we are left with a white dwarf a hot burning star core. Now for massive stars, they live far shorter lives burning out and becoming red supergiants at around 3 million years. From a red supers giant they explode into a supernova that can either create a neutron star or a black hole.
We track stars with a chart called the HR Diagram it helps scientists indefinitely the qualities of stars and show the relationship between temperature and luminosity (brightness) of a star. It reads top right hot and bright, top left cool and dim, bottom right hot and dim, with the last corner being cool and dim. So a quicker way to say this would be the higher on the y- axis you go the brighter it gets and the farther left on the x- axis you go the hotter the star. Just to address the elephant in the room: Yes, the hotter the farther left it goes even though most axis go the other way, it just is what makes this graph unique. So moving on the four main types of stars on this graph are Giants, Super Giants, White Dwarfs, and Main Sequence. Our Sun is in the main sequence that includes 90% of stars, the main sequence is the line that stars usually follow of heat and light.
A galaxy is a large cluster of gas dust and stars, large meaning 100,000 - trillions that are bound together with their own gravity. Not all galaxies are the same so we made classifications based on shape and what they hold, elliptical galaxies are round and contain most old stars and very little dust and gas, spiral galaxies like our own are a disk shaped bulge with many arms sticking out in a spiral shape with old stars in the middle and new stars at the arms, and finally irregular are odd shaped galaxies with a lot of dust and gas they contain mostly new stars. That's really all we learned about galaxies.