Hints: cosmology galaxy oxygen carbon the Milky Way
The ultimate aim of cosmology is to understand how the universe was formed. One of the most important questions is how galaxies were created, because without them we wouldn't exist.
Galaxies contain almost all of the stars we see in the universe and, maybe the places where all stars in the universe will be created. And stars are what produce oxygen, carbon, planets, everything you need for life. And without life you don't get astronomers.
We see our galaxy, the Milky Way, as a band of stars in the sky. In fact, it is a giant rotating disc, 200,000 light years wide. It contains over 200 billion stars like our own sun, circling slowly around the center.