Planets, Stars, Galaxies, and the Universe



About Lesson 8

Beginning with this lesson, we are now in the part of the course that I am grouping as Unit 3. In Lessons 8 - 10, we will address galaxies and cosmology. Having only three lessons means we again have to refer you to outside resources for more in-depth discussions of certain topics, but we will be moving outward from the Sun and the stars to understand the Milky Way, then the nearby galaxies, and finally the Universe as a whole.

From our location here on Earth, for centuries astronomers have studied the night sky to determine how the Earth fits into the structure of the Universe. The earliest theories that we studied suggested that the Earth was the center of the universe and all other objects revolved around our stationary planet. The first large shift in our understanding came when it was shown that the Sun was the center of our Solar System, and the Earth was simply one of several planets orbiting the Sun. Now that we understand the stars and star clusters, we can take our next step and figure out how the stars are distributed inside the Milky Way Galaxy. This will also allow us to understand how the Milky Way Galaxy fits into the structure of the entire Universe.

What will we learn in Lesson 8?

By the end of Lesson 8, you should be able to:

  • explain the geometry of the Milky Way and why it appears as a band in the sky as seen from Earth;
  • identify the different stellar populations present in the Milky Way and their distribution within the Galaxy;
  • describe the evidence for a supermassive black hole in the center of the Galaxy.

What is due for Lesson 8?

Lesson 8 will take us one week to complete.

Please refer to the Calendar in ANGEL for specific time frames and due dates.

There are a number of required activities in this lesson. The chart below provides an overview of those activities that must be submitted for Lesson 8. For assignment details, refer to the lesson page noted.

Lesson 8 Requirements
Requirement Submitting your work
Lesson 8 Quiz Your score on this quiz will count towards your overall quiz average.
Capstone Project During Lesson 8, you will begin work on the Capstone Project and submit Part 1.


If you have any questions, please post them to Piazza not email). I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.