- Galileo Galilei (1564-1642)
- Born in Italy.
- On learning about the invention of telescopes, he built his own.
- Through his telescope, he saw the craters and the mountains of the Moon, the four satellites of Jupiter, the phases of Venus, and many stars in the Milky Way.
- He was forced by the Church to denounce the theory that Earth moves around the Sun.
- Born in Germany.
- He discovered the planet Neptune, whose existence had been postulated by Leverrier.
- Born in Ukraine.
- He showed that stars shine by nuclear reactions, mainly from the conversion of hydrogen into helium.
- He believed that the creation of Earth resulted from a hot big bang.
- He felt that remnants of the big bang in the form of weak radiation are coming to Earth from all directions.
- Born in Scotland.
- Upon developing a photograph of a comet, he discovered that it showed hundred of stars as well.
- Through future work in this line, he started the construction of a photographic atlas, which was completed after his death.
- Born in Holland.
- Although deaf and dumb and dying very young, he studied variable stars.
- He discovered that Algolis is not a variable star, but one of two stars known as eclipsing binaries. He found the same for Beta Lyrae, which lies close to Vega.
- He also discovered Delta Cephei, a true variable.
Johann Gottfried Galle (1812-1910)
George Gamow (1904-1968)
David Gill (1843-1914)
John Goodricke (1764-1786)