Planets, Stars, Galaxies, and the Universe



We often get asked what the difference is between astronomy and astrophysics. There is a story (probably apocryphal) that is attributed to different astronomers that goes something like, "When I'm on a plane, if I'm feeling sociable and want to talk, if the person sitting next to me asks me what I do, I tell them that I'm an astronomer. If I don't want to talk and want to sleep, I tell them I'm an astrophysicist."

A better way to think about the difference is that astronomy is all about the observation of objects and phenomena in space. For example, you could consider mapping all of the bright stars' locations as astronomy. You could also consider measuring the colors, brightnesses, and velocities of those stars astronomy. We are moving into the study of astrophysics, and now that we know how the properties of stars are measured, we can use those properties to reveal the true nature of stars, including their evolution. Stay tuned.

Activity 1 - Lesson 4 Quiz


First, please take the Web-based Lesson 4 quiz.

  1. Go to Canvas
  2. Go to the "Lesson 4 Quiz" and complete the quiz.

Good luck!

Activity 2 - Lesson 4 Practice Problems


There is a second quiz for this lesson that contains several short math problems. While I expect you to complete the quiz and to give it the same effort you would for a graded assignment, for these problems you will only be graded on completion and not on the accuracy of your answers. Your participation in this quiz will count in lieu of a discussion forum for this lesson.

  1. Go to Canvas.
  2. Go to the "Lesson 4 Practice Problems" and complete the quiz.

Reminder - Complete all of the lesson tasks!

You have finished the reading for Lesson 4. Double-check the list of requirements on the Lesson 4 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.