AST 112 - Chapter 28 (part 2) - Week 7

Galaxy clusters are distinguished by having a high concentration of what type of galaxies near their center?

Giant elliptical galaxies

The Milky Way Galaxy is part of what structure?

A smaller galaxy group called the Local Group

How much of a galaxy cluster’s mass does the luminous matter in stars and galaxies constitute?

3%

Gravitational Lensing, as observed in galaxy clusters, is described as?

it is the bending of light from the background galaxies by the gravity of the galaxy cluster

What is the primary reason behind the lack of Spiral Galaxies in the central regions of rich galaxy clusters?

They are believed to merge into larger elliptical galaxies

How does dark matter differ from the matter we can see?

Dark matter is collision-less and only interacts gravitationally

What phenomenon allows us to map the dark matter within clusters by observing the distortion of shapes of background galaxies?

Gravitational lensing

What is the primary way scientists infer the existence of dark matter?

Through its gravitational effect on visible objects

What evidence from our Milky Way Galaxy indicates the presence of dark matter?

Stars’ velocities remaining mostly flat out to large radii

What method is not used to detect dark matter in galaxy clusters?

Measuring the temperatures of stars within the galaxies