Difference between quasar and Active Galactic Nuclei?
Are there any differences between quasars and Active Galactic Nuclei (AGN)? As I understand it, they are both caused by extremely luminous electromagnetic emission from material accreting onto a super-massive black hole. If they have the same source, is there still some fundamental difference between them (and if so what is it) or are they two names for the same thing?
A quasar is a type of AGN. Its main property is that it's galaxy axis points towards the earth and this way we receive its light and radio signals. That's why they are one of the most energetic AGN. Here you can see a relation of all the AGN types: http://en.wikipedia.org/wiki/Active_galactic_nucleus#Summary