Question 1

Quasars were originally identified because

Accepted Answer

Quasars were originally identified as strong radio sources, which is why they were named "quasi-stellar radio sources."

Question 2

An abnormally luminous spiral galaxy is called a _____.

Accepted Answer

Seyfert galaxies are a class of galaxies with nuclei that produce spectral line emission from highly ionized gas. They are a subclass of active galaxies and are characterized by their extremely bright centers, which can outshine the entire rest of the galaxy. This luminosity is thought to be largely due to the presence of a supermassive black hole at the galaxy's center, which is actively accreting matter.

Question 3

Located around a black hole, this is a very intense radiation source:

Accepted Answer

An accretion disk around a black hole is a very intense radiation source. This occurs as matter is pulled towards the black hole, heats up due to friction and gravitational forces, and emits radiation before crossing the event horizon.

Question 4

Electrons spiraling along magnetic lines cause _____.

Accepted Answer

Synchrotron radiation is emitted when electrons are accelerated in a magnetic field, causing them to move in a curved path or spiral. This phenomenon is distinct from cyclotron radiation due to the relativistic speeds of the electrons involved in synchrotron radiation, leading to more intense and broad-spectrum emissions.

Question 5

These are very active galaxies and very luminous in some or many wavelengths; they are called
_____.

Accepted Answer

The answer of These are very active galaxies and very...

Question 6

The center of a quasar is most likely a _______.

Accepted Answer

The answer of The center of a quasar is most...

Question 7

AGN's are thought to be reinvigorated quasars.

Accepted Answer

AGNs, or Active Galactic Nuclei, are indeed thought to be a form of reinvigorated quasars. Both phenomena are powered by accretion of material onto supermassive black holes at the centers of galaxies, with quasars being the most luminous and active examples. As quasars consume the material around them and this material becomes less abundant, their luminosity can decrease, transitioning them into a less active state. However, if new material is introduced into the vicinity of the black hole, it can reignite the AGN activity, effectively reinvigorating the quasar.

Question 8

Quasars are always large radio sources.

Accepted Answer

Quasars are highly luminous objects powered by black holes at their centers, but not all quasars are strong radio sources. Some are radio-quiet, emitting very little radio emission compared to their optical and ultraviolet emissions.

Quiz 78: Active Galactic Nuclei