Chapter 12 Lesson 4

What percentage of the universe's mass is hypothesized to be dark matter?

• 50%

• 70%

• 90%

• 100%

What do scientists not know about dark matter?

• Its color

• Its material composition

• Its temperature

• Its location

What surrounds the disk of a spiral galaxy?

• A ring of fire

• A cloud of gas

• A spherical halo or globular clusters

• A belt of asteroids

What is a characteristic of elliptical galaxies compared to spiral galaxies?

• They have more young stars

• They contain more dust and gas

• They have a higher percentage of old, red stars

• They have a more defined structure

How do scientists suspect elliptical galaxies form?

• By the collision of asteroids

• By the gravitational merging of two or more spiral galaxies

• By the explosion of a supernova

• By the collapse of a black hole

What is a characteristic of irregular galaxies?

• They are perfectly spherical.

• They have a defined spiral structure.

• They are oddly shaped.

• They have no stars.

What often causes the formation of irregular galaxies?

• The gravitational pull of neighboring galaxies.

• The explosion of a supernova.

• The collision of black holes.

• The presence of dark matter.

What do irregular galaxies contain?

• Many old stars and no star formation.

• Many young stars and areas of intense star formation.

• Only planets and no stars.

• Only black holes.

What is the name of the irregular galaxy shown in the image?

• NGC 5982

• NGC 1427A

• NGC 1300

• NGC 4258

How are galaxies held together in the universe?

• By magnetic fields.

• By gravity in groups called clusters.

• By dark energy.

• By cosmic rays.

Tags

NGSS.HS-PS2-4