Stars, right? What else? Almost all those tiny spots you see on nightsky are stars. How many stars can be seen without any equipment? Millions? No, around 1000-1500 in cities and around 3000 in countryside. There are so many stars above that a human being cannot just handle them all. Therefore the stars are grouped into constellations, groups of stars. Those constellations are usually related to some mythology, such as greek and Babylonian mythology. Grouping stars into constellations helps human beings to manage that big amount of information.

Some stars form clusters, such as Pleiades. Many stars are binary stars which is a stellar system consisting of two stars orbiting around their center of mass. For each star, the other is its companion star. Some of the stars are variable stars which have alternating brightness. The alternating cycle can take days or even years, but it can be very fast as well, e.g. hours. Some stars are kefeids, whos brightness changes in a predictable amount of time.

Every single star you see up there belongs to the Milky Way galaxy which is a huge group of stars. The Milky way includes billions of stars and the “belt of stars” of the milky way can also be seen on nightsky. The Milky Way is surrounded by ball-shaped star clusters. The space is not actually “empty” Instead there is matter between the stars that you cannot see. An example of such matter is the M42 Nebula in Orion constellation. New stars are born in this kind of nebulae.

Galaxies, such as M31 Andromeda galaxy, are huge groups of stars. Even though galaxies are huge groups of stars, they are not the biggest element. Groups of galaxies are much bigger. In addition to these star-based formations, there are planets, meteors, comets and the moon. The satellites orbiting the Earth should not be forgotten.

So, there are lots of stars up there in different formations. You don’t watch just stars up there, but various elements including lots of stars.

Image source: http://fi.wikipedia.org/wiki/Komeetta