Page:Illustrated Astronomy.pdf/14

 Even though it is impossible to define an exact age for our Galaxy, we can say that it is almost as old as the Universe itself. Some of the star groups orbiting the Milky Way (known as globular clusters) are nearly 12.5 billion years old.

About 4.5 billion years ago, a great cloud of gas and dust, located at one of the spiral arms of the Milky Way, started to shrink and got divided into smaller and denser clouds. In so doing, hundreds or even thousands of stars of different sizes were formed. Among them is the Sun, that since then is orbiting around the center of the Galaxy, apart from other hotter stars and many other tinnier and colder ones.