When we look at the stars we are looking back in time. For example it takes light from the sun about 8 minutes to reach us. So we are looking at the sun as it was 8 minutes ago. The andromeda galaxy is about 2.5 million light years away. So when we look at it we are seeing it as it was 2.5 million years ago - we are seeing it as it was before humans even existed. In fact when scientists look at the cosmic microwave background they are looking at the heat from just after the Big Bang 13.8 billion years ago. The light from just after the Big Bang has been traveling for 13.8 billion years before it hits our eyes. So we can look so far back in time we can almost see the beginning of the universe itself.

That we can see stars that no longer exist because the light just has so far to travel, our world is so small and insignificant.

The largest star we've found so far, is so big that if it replaced our sun, it would reach out to Saturn. Just imagine how big its solar system could be.