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Astronomer · 1564 CE – 1642 CE

Galileo Galilei

History of AstronomyThe Scientific Revolution

Biography

Galileo Galilei turned the newly invented telescope to the sky in 1609 and changed astronomy forever. He found four moons circling Jupiter, mountains on the Moon, countless stars in the Milky Way, and the phases of Venus — direct evidence against the geocentric model. Condemned by the Inquisition in 1633, he is remembered as a founder of observational science.

Scientific contributions

  • Pioneered telescopic astronomy (1609–1610)
  • Discovered the four large moons of Jupiter
  • Observed the phases of Venus, supporting heliocentrism

Major discoveries

Major publications

Observatories, instruments & objects

Knowledge connections

Sources & references

The primary and reference sources this topic draws on.

  • BritannicaEncyclopaedia Britannica

    General reference for the history of astronomy, biographies, and cultural context.

  • IAUInternational Astronomical Union

    Official naming, definitions, constellation boundaries, and astronomical nomenclature.