Luna 1 became the first artificial object to enter heliocentric orbit after escaping Earth’s gravity in January 1959.
The Soviet spacecraft was launched on 2 January 1959 as part of an attempted lunar impact mission. A guidance error caused it to miss the Moon by about 5,995 kilometres, but the probe still escaped Earth’s gravitational influence and entered an orbit around the Sun between the orbits of Earth and Mars.
Luna 1 also made several important measurements. It detected the solar wind, provided evidence that the Moon has no substantial global magnetic field, and passed near the Moon on 4 January 1959. The spacecraft was originally called Mechta, meaning “Dream,” and was later renamed Luna 1.
Luna 2 achieved the first human-made impact on the Moon later in 1959. That makes Luna 1 the first solar-orbiting artificial object, not the first spacecraft to reach the lunar surface.