OpenStax Astronomy Textbook
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Free, peer-reviewed college textbook covering the solar system, stellar evolution, galaxies, and cosmology, with worked problems and figures. Readers gain the standard one- or two-semester introductory survey without needing calculus.
More resources on Introduction to Astronomy
Sky Tour
When you head outdoors tonight, take Sky & Telescope's Sky Tour astronomy podcast with you for a guided tour to the night sky. Learn what constellations are visible, find out where and when you'll see the planets, and catch each month's celestial highlights, from meteor showers to eclipses.
Kurzgesagt - In a Nutshell
Beautifully animated science explanations covering astrophysics, biology, philosophy, and speculative scientific concepts.
CrashCourse Science
Engaging video courses covering physics, chemistry, biology, astronomy, and ecology with clear explanations and animations.
stellarium.org
Stellarium is a free, open-source planetarium software that renders realistic night skies—stars, planets, constellations, and deep-sky objects—for any date, time, and location. The site offers downloads for multiple platforms and extensive documentation, tutorials, and examples to help you explore and learn astronomy.
nasa.gov
NASA.gov is the official site of the U.S. space agency, offering mission news, research results, data, and STEM education resources. It features engineering articles, technical briefs, simulations, multimedia, and classroom materials for students and educators.
Astronomy Picture of the Day (APOD)
Explore the universe with NASA's Astronomy Picture of the Day! Discover stunning space imagery and learn about the cosmos.