CC #39: Galaxies, part 2

Other than their shape, how else are galaxies classified?

• By their behavior

• By their location

• By their mass

• All of the above

All of these things are peculiar about the object 3C273 discovered in the 1960s, EXCEPT for:

• It is 2 billion lightyears distant (very far away)

• It emits an unusual amount of radio radiation

• It emits over 4 trillion times the energy that the Sun does

• It is an unusually large blue star

What was the name given to objects like 3C273 that emit very large amounts of radio waves?

• Hypernovae

• Peculiar galaxies

• Quasars

• Supermassive black holes

What powers active galaxies?

• Collisions with other galaxies

• Supernovae explosions

• Supermassive black holes

• Dark matter

What phenomenon heats the material in an accretion disk around a black hole?

• Nuclear fusion

• Magnetic fields

• Friction and other forces

• Solar winds

Which of the following is NOT true about the supermassive black hole at the center of the Milky Way?

• It has a mass of about 4 million solar masses

• It makes up a majority of the mass of the entire Milky Way

• It is currently quiescent (it is dormant and not actively feeding)

• It may one day become active again as a result of a galactic collision

What is the name of the neighborhood of nearby galaxies which the Milky Way is a part of?

• The Virgo Cluster

• The Local Group

• Sagittarius

• The Galactic System

Astronomers have discovered that the Andromeda galaxy is "headed right for us!" What is the fate of the Milky Way and Andromeda galaxies in the distant future?

• They will eventually reach a stable orbit around each other (like a binary star system)

• They will destroy each other

• They will collide and form a new galaxy

• They will drift apart forever

On the largest scale, the matter in the Universe is structured into interconnected filaments with empty voids in between, overall resembling:

• A sphere

• A flat disk with spiral arms

• A sponge

• A spiky ball

What is the estimated number of galaxies in the Universe?

• About a trillion

• About a hundred billion

• About a hundred million

• About a million