1957    Space Race: M.I.T. scientists calculate Sputnik I's booster rocket's orbit.

1957    Sputnik program: The Soviet Union launches ''Sputnik 2.'' On board is the first animal to enter orbit, a dog named Laika.

1958    The Soviet satellite Sputnik 2 falls from orbit after a mission duration of 162 days.

1964    The Soviet Union launches the Voskhod 1 into Earth orbit as the first spacecraft with a multi-person crew and the first flight without space suits

1975    Apollo-Soyuz Test Project: An American Apollo and a Soviet Soyuz spacecraft dock with each other in orbit marking the first such link-up between spacecraft from the two nations.

1983    Pioneer 10 travels beyond Pluto's orbit.

1995    51 Pegasi is discovered to be the first major star apart from the Sun to have a planet (and extrasolar planet) orbiting around it.