History of science: Galileo Galilei was an Italian astronomer who accomplished which of the following? Focus on a landmark telescopic discovery in 1610 that supported heliocentric ideas. Choose the correct statement.

What is being asked?Identify a definitive astronomical achievement of Galileo.

Given data

• Timeframe: Early 17th century (1610)

Concept/ApproachGalileo did not invent the telescope but improved it and used it to make major discoveries, including the four largest moons of Jupiter—Io, Europa, Ganymede, and Callisto—bolstering heliocentric arguments.

Step-by-step reasoning1) Evaluate options: telescope invention predates Galileo; Uranus was discovered by William Herschel (1781); geocentric model is pre-Copernican.2) Galileo's well-known, correct achievement is discovering Jupiter's four large satellites in 1610.

Common pitfallsAttributing telescope invention or Uranus discovery to Galileo.

Final AnswerDiscovered four large moons of Jupiter (the Galilean satellites)