Learn Astronomy

Stars, planets, and cosmology. A free, structured curriculum: 5 units · 20 lessons · self-paced.

Unit 1: Theory of Astronomy

Lesson 1.1: What Is Astronomy: Definitions and Scope

Lesson 1.2: Foundational Principles and Axioms

Lesson 1.3: Key Theorems and Laws

Lesson 1.4: How the Theory Was Developed

Unit 2: Core Methods and Approaches

Lesson 2.1: Standard Methods and When to Use Them

Lesson 2.2: Step-by-Step Problem-Solving Process

Lesson 2.3: Tools and Notation

Lesson 2.4: Choosing the Right Approach

Unit 3: Guided Practice

Lesson 3.1: Worked Examples: Simple Problems

Lesson 3.2: Worked Examples: Moderate Complexity

Lesson 3.3: Independent Practice Set

Lesson 3.4: Checking Your Work and Self-Assessment

Unit 4: Advanced Methods

Lesson 4.1: Advanced Techniques and Shortcuts

Lesson 4.2: Multi-Step and Compound Problems

Lesson 4.3: Proof-Based and Analytical Thinking

Lesson 4.4: Connecting Methods Across Topics

Unit 5: Applied Astronomy

Lesson 5.1: Astronomy in Real-World Contexts

Lesson 5.2: Modeling and Estimation

Lesson 5.3: Data Interpretation and Analysis

Lesson 5.4: Cross-Disciplinary Applications

Sample lesson preview

What Is Astronomy: Definitions and Scope

Understand what Astronomy is and why it matters.

Astronomy is best understood through its purpose: what problem does it solve, or what need does it address? Rather than starting with a textbook definition, think about when and why people encounter Astronomy in real life. Understanding the "why" first makes the technical details much easier to grasp. The simplest test of understanding: can you explain it in one sentence to someone who's never heard of it?