Chapter 17

Question 1

What is a galaxy

Answer 1

It is an immense isolated cloud of hundreds of millions to hundreds of billions of stars and vast clouds of interstellar gas

Question 2

What galaxies can be seen without the aid of a telescope

Answer 2

Andromeda and the large and small Magellanic Clouds

Question 3

Who identified the large and small magellanic

Answer 3

Abd Al-rahman Al-Sufi

Question 4

Who observed “fuzzy” objects in the 18th century

Answer 4

Charles messier

Question 5

Who systematically mapped the heavens in the 19th century

Answer 5

William Herschel, they created the new general catalog

Question 6

Who determined that galaxies can be divided based of their shape into three types and two sub types

Answer 6

Edwin Hubble

Question 7

What are spiral galaxies

Answer 7

They have two or more arms winding out the center that look like they’re spinning, classified with the letter S and then followed by a letter from a-d to determine how large the nucleus is or how wound up the arms are

Question 8

What are elliptical galaxies

Answer 8

They are smooth and featureless, classified with the letter E and followed by 0-7 to express flatness

Question 9

What are irregular galaxies

Answer 9

They neither have arms or uniform appearance, the stars seem to be scattered randomly, classified as Irr

Question 10

What are barred spirals

Answer 10

These are spiral galaxies whos arms emerge from the ends of elongated central region rather than the core of the galaxy, classified with the letters SB and followed by the letters a-d. the Milky Way is probably a SB galaxy

Question 11

What are S0 galaxies

Answer 11

They are disk systems with no evidence of arms, they are thought to be an in between of S and E. S0 lacks gas to produce O and B

Question 12

What type of star types are in spiral galaxies and what is it’s interstellar content

Answer 12

Pop 1 and pop 2, it’s interstellar content is 15% by mass in disk

Question 13

What types of stars are in elliptical galaxies and what is it’s interstellar content

Answer 13

Only pop 2 and it’s interstellar content us very low density

Question 14

What types of stars are in irregular galaxies and what is it’s interstellar content

Answer 14

Blue stars, it’s interstellar content is as much as 50% by mass

Question 15

What method is used to measure the distance of galaxies

Answer 15

The standard candles method

Question 16

What are the standard candles

Answer 16

They are usually cepheid variables, supergiant stars, planetary nebulas, supernovas etc.

Question 17

What do all galaxies do relative to the Milky Way

Answer 17

They move away from it

Question 18

What is the reason radial speeds increase

Answer 18

They increased with a galaxy’s distance, this is called recession velocity

Question 19

What are galaxy clusters

Answer 19

Galaxies held close together by their mutual gravity

Question 20

How close are galaxy clusters together

Answer 20

Several million light years across

Question 21

What group does the Milky Way belong to

Answer 21

The local group

Question 22

How many members does the local group contain

Answer 22

Around 30 members, with the largest 3 being M31, M33, and the Milky Way. Most of the local group galaxies are feint/small “dwarf” galaxies

Question 23

What are superclusters

Answer 23

A group of galaxy clusters that attract more clusters

Question 24

How many galaxies does a supercluster contain

Answer 24

It contains half a dozen to several dozen galaxy clusters that spread over tens to hundreds of millions of light years

Question 25

What shape do superclusters have

Answer 25

Irregular shape