Voyager 1

Voyager 1 has been the farthest spacecraft from Earth since February 1998. It entered interstellar space in August 2012 and travels at about 17 km/s. NASA expects it to be one light-day away, 25.902 billion km, on 18 November 2026.

Its distance grows by roughly 540 million km each year, so the figure is only accurate for a given date.

Context

Voyager 1 was launched on 5 September 1977, a few weeks after its twin Voyager 2, to study Jupiter and Saturn. It flew past Jupiter in 1979 and Saturn in 1980, and its close look at Saturn's moon Titan sent it out of the plane of the planets. After its planetary tour it kept travelling at about 17 km per second.

In 2012 the probe crossed the heliopause, the boundary where the Sun's wind gives way to the plasma between the stars. Scientists confirmed the crossing from changes in its plasma wave instrument and charged-particle detectors, and it became the first human-made object to enter interstellar space. Its twin, Voyager 2, followed in 2018.

The spacecraft carries a gold-plated phonograph record with sounds and images of Earth. Its power source, a radioisotope generator, produces less each year, so engineers have been switching off instruments to extend operations. Radio signals take around 22 hours or more to reach it, so distance quoted here applies only to a specific date.