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Ch 23: Galaxies: Properties & Characteristics

About This Chapter

Watch online video lessons about galaxies and learn about black holes, dark matter, quasars and more. These lessons are just a portion of our college-level astronomy course.

Galaxies: Properties and Characteristics - Chapter Summary and Learning Objectives

Let the lessons in this chapter take you on a virtual tour of galaxies, groups of dust, gas and stars that rely upon gravity to keep them together. In this chapter, our knowledgeable and experienced instructors will use short, fun-to-watch videos, online self-assessments and lesson transcripts to teach you about the different types of galaxies, including their distinguishing features and parts. Rewatch the videos as often as you wish to make sure that you understand the presentations, then use the handy quizzes to test your own knowledge of astronomy and galaxies. If you find yourself stuck on a particular topic, you can even post a question to the instructor!

In this chapter, you'll learn:

  • How the Hubble Tuning Fork is used to classify galaxies
  • How to measure galaxies
  • How stars move around in galaxies
  • How matter is recycled in the Milky Way
  • How black holes are formed

VideoObjective
Links in the Distance Chain Describe the components of the distance chain, including supernovae.
The Distribution of Galaxy Properties Along the Hubble Tuning Fork Describe the characteristics of galaxies within the context of the Hubble Tuning Fork.
Types of Spiral GalaxiesDifferentiate among barred spiral, lenticular and normal spiral galaxies.
The Collision and Assembly of GalaxiesDemonstrate your understanding of starburst galaxies
Measuring the Properties of Distant GalaxiesExplain how diameter, distance, diameter and mass of galaxies are calculated.
Characteristics of Stars' Orbits in the Galaxy Learn more about stars' motion around galaxies.
What Are the Different Types of Galaxy Clusters?Name the different kinds of galaxy clusters.
Hubble's Law and Hubble's Constant Demonstrate your understanding of these astronomical concepts.
Dark Matter and Gravitational LensingProvide definitions for dark energy and matter, and explain how they differ from each other.
What are Quasars?Provide a definition for a quasar.
What are Active Galactic Nuclei? Cite the differences between active and normal galaxies.
What Are Supermassive Black Holes? Understand what black holes are and how they are formed.
Recycling in the Milky Way Learn how substances and materials are re-used through galactic processes.
Disk and Spheroidal Components of a Spiral Galaxy Identify the disk and spheroidal parts of a galaxy.
Stellar Populations in the Milky Way Find out about stars in galaxies, from where they're located to how they behave.
Types of Gas in the Disk of the Galaxy Identify common gasses and how they appear through observation.
Locating the Andromeda Galaxy Using Stars Identify the calculations used by Hubble to determine galaxy locations.

15 Lessons in Chapter 23: Galaxies: Properties & Characteristics
The Collision & Assembly of Galaxies

1. The Collision & Assembly of Galaxies

This lesson will talk about how the assembly and collision of galaxies is actually related, what starbursts are, what will happen to our own galaxy in four billion years, and why our galaxy is a galactic cannibal!

The Distribution of Galaxy Properties Along the Hubble Tuning Fork

2. The Distribution of Galaxy Properties Along the Hubble Tuning Fork

This lesson will explore Edwin Hubble's famous classification scheme. We'll go over the major morphological differences between the categories of galaxies and the differences within them.

Types of Spiral Galaxies

3. Types of Spiral Galaxies

Spiral galaxies are classified into several different types, depending on the characteristics of certain parts of their galaxy. Specifically, this lesson will go over Hubble's classification scheme of spiral galaxies with a small nod to lenticular galaxies as well.

Galaxy Collisions: Ring & Elliptical Galaxies

4. Galaxy Collisions: Ring & Elliptical Galaxies

This lesson will discuss the collisions between galaxies and what happens to the stars within them. It will also cover what a ring galaxy is and how it forms, as well as where elliptical galaxies are most common.

Links in the Cosmic Distance Ladder

5. Links in the Cosmic Distance Ladder

This lesson goes over the important basics regarding the cosmic distance ladder and primary, secondary, and tertiary indicators. It will also define standard candles and parallax.

Hubble's Law & Hubble's Constant

6. Hubble's Law & Hubble's Constant

This lesson will go over and define the Hubble Law and Hubble constant. We'll not only do a practice problem but also define conceptually what these two things mean to our cosmos.

Measuring the Properties of Distant Galaxies

7. Measuring the Properties of Distant Galaxies

This lesson will go over a couple of methods astronomers use to find out the properties of a distant galaxy, namely, its distance away from us and its mass.

Characteristics of Stars' Orbits in the Galaxy

8. Characteristics of Stars' Orbits in the Galaxy

This lesson will explore the spherical component and disk of the galaxy to find out what orbital tendencies stars and star clusters have within each section of the Milky Way Galaxy.

Dark Matter & Gravitational Lensing

9. Dark Matter & Gravitational Lensing

This lesson will describe what dark matter is, how much of a cluster of galaxies is made of it, where it's located, and how all of this is related to gravitational lensing.

What Are the Different Types of Galaxy Clusters?

10. What Are the Different Types of Galaxy Clusters?

This lesson will define five different types of clusters: rich, poor, irregular, regular, and superclusters. We'll also find out what voids are and what the Local Group is.

What are Active Galactic Nuclei?

11. What are Active Galactic Nuclei?

This lesson explores and defines active galaxies and active galactic nuclei. You'll learn how they relate to quasars and how big active galactic nuclei are thanks to the observations of the properties of light.

Seyfert Galaxies & Double-Lobed Radio Galaxies

12. Seyfert Galaxies & Double-Lobed Radio Galaxies

This lesson will cover two particular kinds of active galaxies called Seyfert galaxies and double-lobed radio galaxies and their peculiarities, such as hot spots and synchrotron radiation.

What Are Quasars?

13. What Are Quasars?

This lesson will go over the odd-sounding term quasar. You'll learn how the term appeared, the different kinds of quasars, and what they are actually believed to be.

What Are Supermassive Black Holes?

14. What Are Supermassive Black Holes?

This lesson will explain to you what a supermassive black hole is, where they're found, how large they are, how they likely formed, and what they emit into space.

Active Galactic Nuclei & the Unified Model

15. Active Galactic Nuclei & the Unified Model

This lesson will explain the unified model, a model developed by astronomers that tries to help explain how it is that supposedly different objects are really the same thing viewed from different angles.

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