The space age enters the sky

The discovery itself took place on 18 February; public announcement and naming came later.

The object initially joined the planetary list and was reclassified as a dwarf planet many decades afterward.

The Soviet Union launched the first artificial Earth satellite from a spaceport in the Kazakh Soviet Republic.

Sputnik 1 began transmitting radio beeps as it orbited Earth, opening new possibilities for tracking a satellite.

Radio signals from Sputnik could be received outside the launch program, making the orbit publicly observable.

The spacecraft became the first successful interplanetary probe to visit another planet.

Mariner 2 measured properties of the planet while passing it without entering orbit.

Mariner 2 showed that interplanetary spacecraft could return measurements from distant worlds.

The flyby provided direct data to compare with Earth-based astronomical observations.

Valentina Tereshkova became the first woman to travel in space.