Christiaan Huygens, using a home-made telescope, describes accurately the rings of Saturn and discovers the planet's largest moon, Titan

Giovanni Domenico Cassini, working in the Paris royal observatory, calculates the distance from the earth to the sun and is only 7% out

A comet intrigues Edmund Halley, who works out that it has been around before

A comet returns exactly at the time predicted by English astronomer Edmond Halley, and is subsequently known by his name

Captain Cook observes in Tahiti the transit of Venus, the primary purpose of his voyage to the Pacific

William Herschel discovers Uranus, the first planet to be found by means of a telescope, and names it the Georgian star

French astronomer Pierre-Simon Laplace publishes his nebular hypothesis, arguing that the planets formed from a mass of incandescent gas

Wealthy US astronomer Percival Lowell builds an observatory at Mars Hill in Flagstaff, Arizona

The nearest star to earth, the red dwarf Proxima Centauri 4.22 light years away, is discovered by Robert Innes, Scottish director of the Johannesburg Observatory

US astronomer Edwin Hubble proves that the nebula Andromeda is vastly further away than other stars and can only be a separate galaxy

To explain the irregular movement of stars, Swedish astronomer Bertil Lindblad proposes the theory that our galaxy rotates

British astrophysicist Arthur Eddington compares mass and luminosity in The Internal Constitution of the Stars

US astronomer Edwin Hubble uses the red shift of light from galaxies to demonstrate that they are receding from each other and the universe is expanding

British astronomer Fred Hoyle puts forward a 'steady-state' theory of the universe, in which matter is continually created

A 200-inch telescope goes into service at the Mount Palomar Observatory in California

Fred Hoyle, William Fowler, and Margaret and Geoffrey Burbidge explain stellar nucleosynthesis

The USSR launches Sputnik, the world's first artificial satellite

The success of the USSR in launching Sputnik prompts the establishment of NASA in the USA

The Russian spacecraft Sputnik II puts into space a living creature, the dog Laika

Soviet spacecraft Luna 1 goes into orbit round the sun, between the orbits of Earth and Mars

Soviet spacecraft Luna 2 successfully strikes the moon, in the Palus Putredinus region

Soviet spacecraft Luna 3, passing by the moon at a distance of some 40,000 miles, is able to photograph the far side

Soviet cosmonaut Yuri Gagarin becomes the first human to travel in space, orbiting the earth once in Vostok 1

US astronaut Alan Shepard becomes the first American in space, with a suborbital flight in Freedom 7

President Kennedy commits the US to placing a man on the moon and bringing him back safely by 1970