Astronomy 101: Getting to know the Universe

Hawaii, Mauna Kea Observatory
Studying astronomy is the way to find out about the origins and evolution of the cosmos, the stars, galaxies, planets -- and ourselves. Michele Falzone/ Photodisc/ Getty Images

Webster’s Dictionary defines astronomy as “the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties.” Truthfully, though, you could say that astronomy is the study of everything, because everything is a part of the universe.

Step into Astronomy 101

Astronomy 101 is often the first course college students take. It seems like an "easy A" class, because (they think) "How hard can learning about the planets and stars be?"  Once they get into the class, it offers WAY more than a simple trip to the planets.

It opens up the cosmos. And, it also reveals the many varieties of knowledge within the field.

For example, cosmologists study the universe as a whole — its origin and evolution. Astrometrists measure distances in space between objects. Solar physicists focus on the physics of the Sun and its effects on the solar system. Astrophysicists apply physics to the studies of stars and galaxies.Planetary scientists study worlds within our own solar system as well as those orbiting distant stars. Radio astronomers use radio telescopes to study the radio frequencies given off by objects and processes in the universe. Experts in ultraviolet, x-ray, gamma-ray, and infrared astronomy study the cosmos in those wavelengths of light. Through their instruments, we see the universe in a whole new way. There are also mathematical astronomers who use numbers, calculations, computers, and statistics to explain what others observe in the cosmos.

Astronomy is not a “stand-alone” science. It combines areas from a number of other fields including mathematics, chemistry, geology, biology and physics. In fact, physics is such an integral part of the field that many astronomers are also known as Astrophysicists.

Why Study Astronomy?

Why should we study the universe?

As it says above, everything is part of the universe, and that includes us. That's right. You are part of the universe along with the planets, stars, and galaxies. We live on a planet, Earth, which circles the Sun, which is a star called Sol. Just like all the other stars, it's part of the Milky Way Galaxy, and the Milky Way is just one of billions of galaxies in the cosmos. 

Astronomy is also much more than the scientific study of the objects and processes in the universe. It embodies many aspects of human history and culture. People first began to "use" the sky for navigation and calendar-making thousands of years ago. Over time, they began to wonder about those distant objects, and speculate about what they were and their origins. You find a lot of astronomy and mythology entwined together throughout history. Over time, as people became more technologically oriented, they could build instruments to study the stars, planets, and galaxies. That's when the study of the sky moved from philosophy and the realm of myth to the realm of science and mathematics. 

How to Take This Course

This course in astronomy is for you to take at your own speed. The suggested time is ten weeks, one week per lesson.You can, of course, move through the material at a faster or slower pace, it is all up to you.

You're learning new and interesting things, and there are many paths to take as you move through the material.

Here's the best path through the lessons:

  • Read through each lesson.
  • Follow the links within the lesson to find more in depth information
  • Study the related definitions.
  • Complete the associated assignment.
  • Optional: Read some of the Related Resources articles.
  • Move on to the next lesson at your own pace.
  • Once you have completed all ten lessons, take the final quiz and see how you did! 

We'll start with a look into the past. Astronomy is the oldest science, so let’s take a quick look at its history and the remarkable people who brought us to the understanding of the cosmos that we have today.

First Lesson > Astronomy History from Ancient Astronomers through the Renaissance > Lesson 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Expanded and updated by Carolyn Collins Petersen.