Look outward to understand planets, stars, galaxies, and cosmic history.
Explore astronomy through observation, the solar system, stars, galaxies, gravity, and the evolving universe.
Telescopes collect light across the electromagnetic spectrum.
Learn MoreThe Sun, planets, dwarf planets, moons, asteroids, and comets formed from a rotating cloud of gas and dust about 4.
Learn MoreStars shine by fusing lighter elements into heavier ones.
Learn MoreGalaxies contain stars, gas, dust, dark matter, and central black holes.
Learn MoreGravity shapes orbits and large-scale cosmic structure.
Learn MoreEvidence indicates the universe expanded from an early hot, dense state.
Learn MoreTelescopes collect light across the electromagnetic spectrum. Because light takes time to travel, observing distant objects also reveals the universe's past.
The Sun, planets, dwarf planets, moons, asteroids, and comets formed from a rotating cloud of gas and dust about 4.6 billion years ago.
Stars shine by fusing lighter elements into heavier ones. Mass determines a star's temperature, lifetime, and final state, such as a white dwarf, neutron star, or black hole.
Galaxies contain stars, gas, dust, dark matter, and central black holes. The Milky Way is one of billions of galaxies arranged in groups, clusters, and vast filaments.
Gravity shapes orbits and large-scale cosmic structure. An orbit is continuous free fall, balancing forward motion with attraction toward another body.
Evidence indicates the universe expanded from an early hot, dense state. Cosmic background radiation, galaxy motion, and element abundances help scientists reconstruct its history.