sentence: Some black holes are also responsible for quasars.
sentences_after: A quasar occurs when a black hole consumes all the gas surrounding it. As the gas gets close to the black hole itself, it heats up from friction, and glows so brightly that this light can be seen on the other side of the Universe. It is often brighter than the whole galaxy the quasar is in. When astronomers first found quasars, they thought they had found objects close to us. After using a measuring technique called red shift, they discovered these quasars were actually very far away in the universe.
concept_name: black hole
headings: Black hole Formation of black holes Explanation
categories: Stars Astrophysics