What is a quasar? What is their importance?

Hint: A quasar is formed when a super massive black hole at the centre of a galaxy has sufficient material around it to fall into the accretion disc to create the energy. They are very luminous objects found in the cosmos.

Complete answer:
• Quasars are incredibly bright astronomical objects located in the centres of certain galaxies and driven by gas spiralling at high velocity into an exceptionally massive black hole.
• The brightest quasars can outshine all of the stars in the galaxy in which they live, making them visible from billions of light-years away. Quasars are among the most distant and brightly illuminated phenomena known.
• The importance of quasars is that by finding its existence we now know that super massive black holes exist at the centres of young galaxies. Because a quasar is fuelled by a super massive black hole at the centre of a galaxy.
• In case there is sufficient material close to the super massive black hole it will begin to fall into the black hole making an accretion disc. It consumes a lot of time for material to fall into a black hole.
• As more material falls into the accretion disc it gets superheated by friction and gravitational impacts to where it produces large amounts of energy.

Note:
Observations of quasars have found that their brightness may change substantially on timeframes as small as a few days, implying that the entire size of the quasar cannot be more than a few light-days wide. Because the quasar is so compact and bright, the radiation pressure within the quasar must be enormous.