This Guide supports study and revision for IBDP Physics Paper 3, for SL and HL students planning to answer questions on Option Astrophysics. It provides summaries and explanations of key points and concepts for all SL and HL topics, and advice on approaching different question types. Coverage stellar quantities; stellar characteristics and evolution; stellar processes; cosmology; and stellar processes. Key over 50 practice questions, with answers and commentary; worked examples to demonstrate how to solve exam-style questions; exercises to help improve graphing skills; clearly presented graphs and diagrams; and a list of common exam mistakes.