The sun is actually a star. It appears much larger, because it is so much closer. You can try out at home by putting your thumb in front of your eyes, and comparing it to the more distant standing  mum. Mother appears the size of a thumb, because she t is further away. This phenomenon is called a perspective.

The stars are huge fireballs. Actually, they have a huge amount of gas, whose own weight to keep star together. The star is an ongoing fusion reaction, a bit like nuclear power plants. The result is an enormous amount of light, warmth and a lot of different types of invisible radiation.

After Sun the closest star is Proxima Centauri, which is about four light-years away. It is so far away that with the world’s fastest spaceship it would take more than 73 000 years to get there. It is a long time. 73 000 years ago, the cave men learned to use tools and make drawings in the cave walls. The same spacecraft would circulate around the earth in about three quarters of hour.

There is almost infinite number of stars in space. Most of them are so far away that they can not be seen with the naked eye in the night sky. There are much more stars, than there are grains of sand on the beach. Around each star may have planets such as Earth.

Stars form star clusters and galaxies. Galaxy may be hundreds of billions of stars. Galaxies tend to look helical wafer. Our galaxy, the Milky Way, may be visible in the night sky as a light stripe. The Milky Way is a spiral galaxy, but we see it from the inside so it appears as a stripe.