Hello, i want to study by myself these topics because i just learn physics in my classes and i want to discover the Astronomy and Cosmology, if you have links, books pdf, or whatever please tell me! Thanks
We have a 'sticky' thread that gives a good list of introductory online texts on mainstream cosmology. I suggest you read some and ask questions on this (current) thread, because that one is 'locked' to leave in a uncluttered state.
Just beware of all the 'Alternative/Personal Theories' around here - they can be greatly confusing, to say the least.
In addition to Burt's excellent advice I would recommend purchasing a handful of second hand astronomy textbooks. As long as their publication date is within the last twenty years then almost all the important material will be there.
I suggest second hand, since you are a student and most students would welcome the considerable savings. As an example I have a copy of the 2002 Cosmic Perspective, list price $93, purchased for $9 in 2012.
The book used in the intro astronomy elective I took was Explorations: Introduction to Astronomy; Thomas Arny.
If there are any astronomy classes at your university (or go to the website and look up syllabi of other universities) you can see what text book they use. Then you can just buy an older edition for cheap. A student doesn't even need to take many classes at a university if they just buy and read through the text book.