Is the Sun a star or are the stars other Suns?

OK, so far we got some basic ideas about distances, but how do we know that stars and the SUN are similar (or are they!?).

First by knowing their distances we can estimate how bright stars would be if we were close to them and most of the stars would be similar to our SUN. Of course there are some stars which are much much fainter (eg. Proxima Centauri) or much much brigther eg. Mu Cep, Betelguez.

What is in common to all stars or what makes an object a star?

Stars are gaseous massive object which produce energy in their interior. They are hot on their surface and because of that they emit light what we can see and in astronomy we can measure their light and conclude a lot about their properties. So I will just mention to you that there are stars which have mass only one hundredth of mass of the Sun and there are stars with mass up to few tens solar masses. Also stellar temperatures vary from around three thousand degrees to up few tens of thousands degrees (solar temperature is around 6000K).

Here I show you the spectrum of the star (lower panel) HR 4345 and the spectrum of the Sun taken with the same instrument and in the same wavelength range. I hope that you can see the similarity.

In this diagram you can see different properties of the stars and position of the Sun. Of course it is the famous Hertzsprung-Russel diagram. (****I didn't have good colourful one to put it here ****)