CH. 14: Galaxies

Which of the following contributes the largest percentage of total mass of a spiral galaxy?

dark matter

Identify the type of galaxies on the figure that represents Hubble’s tuning fork

left ellipticals, fork S0, top spiral, bottom barred spirals, right irregulars

What does isotropy mean?

the universe is the same in all directions

What does homogeneity mean?

the universe is the same in all locations

What are the methods of determining distances of remote objects?

left to right: radar, parallax, spectroscopic parallax, cepheid variable star, type 1a supernovae

Label the basic parts of the Milky Way galaxy and indicate the total diameter

top to bottom: galactic halo, 300,000 light-years, globular clusters, galactic disk, magellanic clouds

How do astronomers determine the radius of an AGN?

they measure how quickly its light varies.

Summary of the existence of supermassive black holes

Supermassive black holes occur in most, if not all, large galaxies.

The distances to galaxies used to establish Hubble’s law are found from:

standard candles, such as supernova.

What is the size of the light that comes to us from active galactic nuclei from a volume?

about the size of the Solar System

What direction do stars orbit in elliptical galaxies?

stars orbit in random orientations in elliptical galaxies

How is the light in an AGN outburst emitted?

at the same time

List the evidence that there is a supermassive black hole at the center of the Milky Way

X-rays from material that is falling in
strong radio emission from the region of the accretion disk
direct observations of stars that orbit it

Hubble’s law was discovered using measurements of which two properties of a galaxy?

distance and recession velocity

Why might an elliptical galaxy appear round?

it is elongated along one axis, but it is viewed parallel to the long axis.
it has one axis shorter than the other two but is viewed parallel to the short axis. 
all three axes are the same; it is spherical in shape.
all three axes are different lengths, but it is viewed from a special angle.

What direction do stars orbit in the bulge of a spiral galaxy?

irregularly in all directions

What direction do stars orbit in the disk of a spiral galaxy?

together in one direction

What is the general motion for the stars in an elliptical galaxy?

irregularly in all directions

What can happen when galaxies merge?

huge numbers of new stars can form all at once

The figure shows photos of 12 different pairs of interacting galaxies. 

How many of these interactions are occurring between two spiral galaxies?

9

The figure shows photos of 12 different pairs of interacting galaxies. 

How many of these interactions are between two elliptical galaxies?

2

The figure shows photos of 12 different pairs of interacting galaxies. 

How many interactions shown in the figure are between an elliptical galaxy and a spiral galaxy?

1

Identify which type of galaxy is represented in the image

Barred spiral galaxy

Identify which type of galaxy is represented in the image

Dwarf elliptical galaxy

Identify which type of galaxy is represented in the image

Giant elliptical galaxy

Identify which type of galaxy is represented in the image

Unbarred spiral galaxy

Which type of galaxies are star formation rates the highest?

spiral galaxies

How are galaxies classified?

according to their shape

What type of galaxy is shown

spiral

What type of galaxy is the Milky Way?

a barred spiral galaxy

What is the difference between a spiral galaxy and a barred spiral galaxy

Barred spirals sport ribbons of stars, gas, and dust that cut across their centers while unbarred spirals do not