Free online courseDescriptive Astronomy: From Orbits to the Big Bang

Course Description

If you have ever looked up at the night sky and wondered how astronomers know what they know, this course offers a clear, welcoming path from familiar observations to the biggest ideas in modern science. You will build a descriptive, evidence-based understanding of the universe, learning to connect what we see through telescopes to the physical laws that shape planets, stars, and galaxies.

You will start with motion in the sky and the logic of orbits, developing intuition for how gravity organizes solar systems. From there, you will see how astronomers extract information from faint light using practical methods such as spectroscopy and Doppler shifts, turning color and line patterns into clues about composition, temperature, and motion. Along the way, you will develop confidence reading the kinds of arguments astronomers use, where observations, measurement, and model-building work together.

As you move outward in scale, you will trace the formation and structure of our solar system, compare inner worlds and giant planets, and understand the role of smaller bodies like asteroids and comets. You will also explore our Sun as a representative star, linking what happens at its visible surface to the deeper processes that power it over billions of years. This foundation sets you up to interpret starlight, make sense of stellar lifecycles, and see how clusters and diagrams reveal age and evolution.

The course then expands to dramatic endpoints such as white dwarfs, supernovae, and black holes, clarifying the role of spacetime and extreme gravity without losing sight of the observational evidence behind these ideas. You will step into the structure of the Milky Way, the behavior of galaxies and quasars, and the patterns captured by Hubble’s law. Finally, you will tie it all together with the Big Bang model, the cosmic microwave background, and a thoughtful look at life in the universe and the Fermi paradox. Short exercises throughout help you check understanding and turn big concepts into usable knowledge you can apply to new astronomical questions.