Our Earth is inside of one giant universe and inside of thatuniverse there is a galaxy known as the Milky Way which is the galaxy that ourhome is in. The Milky Way is called a spiral galaxy, this is the most commontype of galaxy throughout the universe. A galaxy can be defined as a largenumber of stars that are bound together by gravity. From a far our galaxy lookslike a small band of light across the night sky, this is called a galactic disk.Inside of that galactic disk our galaxy is surrounded by many old stars andstar clusters, these are known as a galactic halo. The galactic halo is aregion is our galaxy that has extended far beyond the galactic disk. Manyastronomers are able to study the halo in our galaxy by looking at variablestars. Astronomers are able to look at these stars because the brightness invariable stars change over time which make the easier to see.
Astronomers canalso study the halo by looking at pulsating variable stars, this is becausethese types of stars vary in their brightness so they can see more over acertain area. The stars that are currently in the galactic halo will be thesame stars that will always be there until they die. This is because no newstars are able to form inside of the galactic halo due to the lack of gassesand dust inside the halo.
However, even though the galactic halo cannot formnew stars, the galactic disk does produce enough gas to the point where newstars can be formed. Due to this, many stars in the galactic disk have recentlybeen formed, and thus are younger. The Milky Way galaxy also consists of a darkhalo and dark matter. Astronomers have said that the dark halo is a regionoutside of the visible halo that is darker and can potentially house darkmatter. The dark matter is what is thought to be mass inside of a galaxy,although this is what it is thought to be, it has not been proven byastronomers that this is exactly what dark matter is.
Astronomers that havebeen studying our galaxy have also found that there is a large amount of energythat is being released from the center of a dark star cluster. This energy issaid to potentially be a giant black hole. Many astronomers who have studiedthis black think that it may have appeared due to a potential supernovaexplosion that may have occurred in the star cluster around it. There is manythings to learn about our home galaxy, The Milky Way, but this is just aglimpse of what makes it possible for us to live here.