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/Approach
Galileo 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 reasoning
1) 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 pitfalls
Attributing telescope invention or Uranus discovery to Galileo.

Final Answer
Discovered four large moons of Jupiter (the Galilean satellites)