Astronomy

An introduction to the branches of astronomy covered in this section

Welcome to Astronomy

Astronomy is the study of everything beyond Earth — planets, stars, galaxies, and the universe as a whole. It's one of the oldest sciences, and also one of the most active today, driven by ever-better telescopes and spacecraft.

What you'll find here

This section is organized into the major branches of astronomy: Planetary Science (planets and moons), Stellar Astronomy (stars, their lives and deaths), Galactic Astronomy (the Milky Way and other galaxies), Cosmology (the universe as a whole), Astrophysics (the physics underlying it all, shared with the Physics section), Astrobiology (the search for life beyond Earth), Observational Astronomy (telescopes and how we gather data), and Space Science (rockets, satellites, and spaceflight).

How to use this section

Each branch has three levels — Student, Advanced, and Expert — so you can start wherever feels right and go deeper whenever you're ready. Many of the branches connect closely with each other and with the Physics section, so feel free to explore in whatever order interests you most.