Learn how galaxies evolve from early gas clouds into complex systems shaped by gravity, star formation, collisions, and dark matter.

Learn how the Sun compares with other stars in size, temperature, composition, energy, and life cycle.

Explore the main ways astronomers estimate galaxy mass, from rotation curves and velocity dispersion to gravitational lensing and dark matter clues.

Learn what nuclear fusion in stars is, how it powers the Sun, and why it creates the elements that shape planets, life, and the universe.

A practical guide to teaching and learning star life cycles through diagrams, models, simulations, and astronomy resources.

Discover how galaxies form from dark matter, gas, star birth, and cosmic mergers, and why their shapes reveal their history.

Learn how novae and supernovae differ in energy, brightness, star systems, and what astronomers observe when each eruption occurs.

Discover what stars are made of, how their composition is measured, and why hydrogen, helium, and heavier elements shape stellar life cycles.

Explore why stars explode, what triggers supernovae, and how these events create heavy elements, neutron stars, and black holes.