Home is a place where we feel safe and secure. Everybody has its own definition of home. For some earth is a home, but point here is we actually live in larger and more vast place than we can ever imagine. I am not talking here about the universe, but our home galaxy "the Milky Way". It is our galactic home. Milky Way has its important for humans because home sweet home. Our galactic home is not just beautiful, but also vast for creatures like us. So far the most complex life in the Milky Way Galaxy is just us.
Artist Impression of Milky Way. Courtesy www2.lns.mit.edu
When it comes down to structure than our galactic home is like a spiral galaxy. A glimpse up at the night sky exposes a wide band of powerful light. Ancients described this band as a river and a path. Milky Way is a barred spiral galaxy and it is about 100,000 light years across. If you take a look from top on the Milky Way Galaxy than you will see arms and recent research shows that the Milky Way Galaxy has four spiral arms (as you can see in the above image). We cannot take a real picture of the Milky Way from above because we are inside of it and using our recent technology we cannot get out of it. So wherever on the internet or any other place you see a picture of the Milky Way Galaxy then keep in mind that it is a picture of some another spiral galaxy, or the interpretation of a talented artist.
The central bulge of the Milky Way Galaxy has a diameter of about 12000 light years. The Milky Way Galaxy has a crown of dark matter that makes up over 90% of its total mass. The crown of dark matter is actually undetectable, however, we know it exists by running some simulations of what the Milky Way would look like and how fast stars orbit inside the galaxy. The heavier it will be the stars should faster orbit.
Image Credit: ESO
Galaxies have billions of stars and the largest galaxy so far known is IC 1101 and it has over 100 trillion stars, other large galaxies can have even more than this. There are also smaller galaxies like the Large Magellanic Cloud and it has about 10 billion stars. Comparing our Milky Way Galaxy with others, we can say that our Galaxy is Middle weight Galaxy. The Milky Way has almost 200 to 400 billion stars, and interesting fact here is when you look up into the night sky the number of stars you can see from any one point on the Earth is just 2,500. Milky Way is full of dust and gas. The Milky Way wasn't always as it looks today as a barred spiral galaxy and yet beautiful. Its size and shape changed with time by eating other galaxies.
It is still doing this today and the Canis Major Dwarf Galaxy is the closest one to the Milky Way Galaxy, so its stars are being added into the Milky Way Galaxy. Before this our galaxy consumed Sagittarius Dwarf Galaxy. The most current approximation of the age of our Universe is about 13.7 billion years. Our milky way Galaxy is very old and about 13.6 billion years old. Oldest stars of our galaxy can be found in globular clusters and depending on these stars we calculated the age of our galaxy. Most galaxies have a super massive black hole at their center and like most of other galaxies in our galactic home also has a super massive black hole in its center. The oldest region of our galaxy is called Sagittarius A* and houses a black hole with a mass of 40,000 Suns. Everything in our galaxy revolves around it even our solar system. There are between 100 billion and 200 billion alien planets in our galactic home so contact with an alien life is not far.