What is an Active Galactic Nucleus (AGN)?

An extremely luminous region at the center of a galaxy where a supermassive black hole is actively consuming surrounding material A region near a galaxy's center where many new stars are being born simultaneously A supernova explosion near the center of a galaxy A collision between two galaxy nuclei during a merger

What is the accretion disk of an AGN?

A flat, rotating disk of superheated gas spiraling into the supermassive black hole, reaching temperatures of billions of degrees in its inner region A ring of solid rocky material orbiting around the black hole like Saturn's rings A disk of dark matter surrounding the galactic center The flat disk of stars that makes up the main body of a spiral galaxy

What is the dusty torus in an AGN, and what role does it play?

A ring of old stars surrounding the galactic center A doughnut-shaped ring of dust surrounding the AGN core that can block our view of the broad-line region depending on the viewing angle A rotating disk of gas that feeds the black hole directly A ring of plasma that generates the magnetic field powering the jets

What is the AGN unified model?

The theory that all supermassive black holes have exactly the same mass The idea that different types of AGN are actually the same structure viewed from different angles A model showing that all galaxies will eventually develop an active nucleus The hypothesis that AGN are powered by dark matter annihilation rather than black holes

What are the relativistic jets seen in some AGN?

Explosions of material ejected when the black hole's gravity reverses Narrow beams of plasma ejected perpendicular to the accretion disk at close to the speed of light Streams of stars flung out of the galaxy by the black hole's tidal forces Bursts of gamma radiation emitted when two black holes merge

What is the broad-line region of an AGN?

Fast-moving gas clouds very close to the black hole that produce broad, smeared-out spectral emission lines A large zone around the galaxy where radio waves are produced The wide outer disk of stars in a lenticular galaxy A region of space between two merging galaxies where star formation is occurring

Is the supermassive black hole at the center of the Milky Way currently an AGN?

Yes — Sgr A* is one of the brightest quasars in the sky Yes — Sgr A* is an active radio galaxy with powerful jets No — Sagittarius A* is currently dormant and barely active, though there is evidence it was active millions of years ago No — the Milky Way has no supermassive black hole at its center

How does the energy output of a bright AGN compare to a normal galaxy?

An AGN produces slightly more energy than a single large star An AGN produces the same amount of energy as a normal galaxy but in radio waves instead of visible light A bright AGN can outshine thousands of normal galaxies, all from a region smaller than our solar system An AGN and a normal galaxy produce exactly the same total energy

What is the narrow-line region of an AGN?

A zone of space around the AGN where radio emission is prohibited The innermost accretion disk where light cannot escape the black hole's gravity Gas further from the black hole that moves more slowly, producing sharp, narrow emission lines in the spectrum A thin beam of radiation produced by the jet of a radio galaxy

What drives the enormous energy output of an AGN?

Nuclear fusion of hydrogen in the accretion disk, much more intense than in normal stars The collision between matter and antimatter at the event horizon of the black hole Gravitational energy released as infalling gas loses energy and heats up in the accretion disk around the supermassive black hole Dark energy stored inside the black hole that is released as it spins