📜 Timeline: The Solar System
12 milestones in the history of the solar system.
Solar System Forms
The Sun and planets form from the gravitational collapse of a molecular cloud over ~100 million years.
Source: Planetary SciencesGalileo Observes Jupiter's Moons
Galileo Galilei discovers the four largest moons of Jupiter, proving not everything orbits Earth.
Source: The Solar SystemKepler's Laws of Planetary Motion
Johannes Kepler publishes his three laws describing how planets orbit the Sun in ellipses.
Source: Planetary SciencesDiscovery of Uranus
William Herschel discovers Uranus — the first planet found with a telescope.
Source: The Solar SystemDiscovery of Neptune
Neptune is discovered based on mathematical predictions of its gravitational effect on Uranus.
Source: The Solar SystemFirst Mars Flyby (Mariner 4)
Mariner 4 performs the first successful flyby of Mars, returning the first close-up images.
Source: The Solar SystemApollo 11 Moon Landing
Neil Armstrong and Buzz Aldrin become the first humans to walk on another world.
Source: The Solar SystemVoyager Grand Tour
Voyager 1 and 2 launch, eventually visiting all four giant planets and entering interstellar space.
Source: The Solar SystemCassini-Huygens at Saturn
The Cassini spacecraft orbits Saturn for 13 years, discovering ocean worlds and studying the rings.
Source: The Solar SystemPluto Reclassified
The IAU redefines "planet," reclassifying Pluto as a dwarf planet.
Source: Pluto and the Developing Landscape of Our Solar SystemNew Horizons at Pluto
NASA's New Horizons performs the first flyby of Pluto, revealing a geologically active world.
Source: The Solar SystemJames Webb Space Telescope
JWST begins observing the solar system and beyond with unprecedented infrared sensitivity.
Source: The Solar System