Since the dawn of the Space Age in the mid-20th century, humanity has been sending spacecraft to explore the far reaches of our solar system and beyond. These robotic emissaries have served as our eyes and ears in the cosmos, providing unprecedented views and insights into the diverse worlds that share our celestial neighborhood.
Among the many spacecraft launched over the past decades, a select few have ventured further than all the others, pushing the boundaries of exploration and our understanding of the universe. These intrepid explorers have not only visited distant planets and moons but have also become the first human-made objects to leave our solar system entirely and enter the vast expanse of interstellar space.
This article takes a closer look at the top five furthest things humans have sent into space. These spacecraft – Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons – represent some of the most remarkable achievements in the history of space exploration. Each of these missions has its own unique story and has contributed to our knowledge of the cosmos in profound ways.
The top 5 furthest human-made objects in space:
1. Voyager 1
Launched on September 5, 1977, Voyager 1 is currently the most distant human-made object from Earth. As of July 2024, it is more than 15.2 billion miles (24.4 billion km) away from our planet, having long since left our solar system. Voyager 1’s primary mission was to fly by Jupiter and Saturn, which it accomplished in 1979 and 1980 respectively. During these flybys, it captured detailed images and data about the gas giants and their moons, revolutionizing our understanding of these distant worlds.
After completing its planetary mission, Voyager 1 continued its journey toward the edge of the solar system. In August 2012, it made history by becoming the first spacecraft to enter interstellar space, the region between stars filled with dilute gas, dust, and cosmic rays. Voyager 1 continues to send back valuable data about this uncharted territory, providing unique insights into the boundary between our solar system and the rest of the Milky Way galaxy.
Voyager 1 is powered by three radioisotope thermoelectric generators (RTGs) which convert the heat from the decay of radioactive material into electricity. While the power output of the RTGs is declining over time, NASA expects Voyager 1 to continue operating at least one science instrument until around 2025. After that, it will continue its lonely journey through interstellar space as a silent ambassador of humanity, carrying with it the famous “Golden Record” containing sounds and images portraying the diversity of life and culture on Earth.
2. Voyager 2
Voyager 2, Voyager 1’s twin spacecraft, was launched on August 20, 1977, on a different trajectory that would allow it to visit all four outer planets – Jupiter, Saturn, Uranus, and Neptune. Like Voyager 1, it flew by Jupiter and Saturn in 1979 and 1980, but then went on to make historic flybys of Uranus in 1986 and Neptune in 1989. These remain the only spacecraft visits to date to the ice giants.
After its Neptune encounter, Voyager 2 also set course for interstellar space. In November 2018, it crossed the heliopause – the boundary where the Sun’s solar wind is stopped by the interstellar medium – at a distance of about 11 billion miles (18 billion km) from Earth. As of April 2023, Voyager 2 is about 12 billion miles (19.3 billion km) from Earth, making it the second-farthest human-made object.
One unique aspect of Voyager 2’s mission occurred in March 2020, when NASA was able to command the spacecraft to fire its trajectory correction maneuver thrusters – dormant since the 1989 Neptune flyby – to help extend its lifetime. Like Voyager 1, Voyager 2 is expected to continue returning scientific data until the mid-late 2020s.
3. Pioneer 10
Pioneer 10 was the first spacecraft to achieve escape velocity from the solar system, and the first to fly by Jupiter. Launched in March 1972, it made its closest approach to Jupiter in December 1973, passing within 81,000 miles (130,000 km) of the planet’s cloud tops. Its images of the gas giant and its moons were the best ever taken at that time.
After Jupiter, Pioneer 10 continued its outward journey, eventually crossing the orbit of Neptune in 1983. In 2003, when it was about 7.6 billion miles (12.2 billion km) from Earth, NASA lost contact with the spacecraft due to the extreme distance and the spacecraft’s steadily weakening signal. As of 2023, Pioneer 10 is estimated to be over 11 billion miles (17.7 billion km) away.
Pioneer 10 carries a gold-anodized aluminum plaque, designed by Carl Sagan and Frank Drake, which features a pictorial message in case the spacecraft is ever found by intelligent life-forms from other planetary systems. The plaque depicts a nude man and woman along with several symbols that are designed to provide information about the origin of the spacecraft.
4. Pioneer 11
Pioneer 11, launched in April 1973, followed its twin Pioneer 10 to Jupiter, making its closest approach in December 1974. It used Jupiter’s gravity to alter its trajectory toward Saturn, becoming the first spacecraft to encounter the ringed planet in September 1979.
During its Saturn flyby, Pioneer 11 came within 13,000 miles (21,000 km) of Saturn’s cloud tops. It discovered two new moons and an additional ring, charted Saturn’s magnetic field and mapped its gravity field. The spacecraft used Saturn’s gravity to propel itself out of the plane of the ecliptic and above the solar system.
Contact was lost with Pioneer 11 in November 1995, when it was about 6.5 billion miles (10.5 billion km) from Earth. As of 2023, Pioneer 11 is estimated to be about 9 billion miles (14.5 billion km) away. Like Pioneer 10, it also carries a gold-anodized plaque with a message for any extraterrestrial intelligence that might find it in the distant future.
5. New Horizons
New Horizons is the first mission in NASA’s New Frontiers program. Launched in January 2006, it’s primary mission was to make the first flyby of Pluto, which it achieved on July 14, 2015, passing 7,800 miles (12,500 km) above the surface of the dwarf planet.
The images sent back by New Horizons revealed Pluto to be a world of surprising geological diversity, with mountains, valleys, plains, and evidence of past and possibly present-day glacial activity. It also studied Pluto’s largest moon, Charon, in detail.
After Pluto, New Horizons continued into the Kuiper Belt, a region of the outer solar system beyond Neptune’s orbit that is home to a large number of small, icy objects. In January 2019, it made a flyby of the Kuiper Belt object 2014 MU69, nicknamed Ultima Thule (later renamed Arrokoth), the most distant object ever visited by a spacecraft.
As of December 2022, New Horizons is over 4.3 billion miles (6.9 billion km) from Earth and still operating. It is expected to continue exploring the Kuiper Belt until the late 2020s or beyond. In the coming decades, it will likely pass the Pioneer probes to become the third most distant human-made object.
Summary
These five spacecraft represent some of the most ambitious and far-reaching explorations in human history. They have not only greatly expanded our knowledge of the solar system but have also become our first emissaries into interstellar space. As they continue their journeys, they carry with them a piece of human curiosity and the spirit of exploration that defines our species.
