paragraph_text: Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth - largest planet by diameter, the third-most - massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near - twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 AU (4.5 billion km). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.

paragraph_text: Jupiter has been called the Solar System's vacuum cleaner, because of its immense gravity well and location near the inner Solar System. It receives the most frequent comet impacts of the Solar System's planets. It was thought that the planet served to partially shield the inner system from cometary bombardment. However, recent computer simulations suggest that Jupiter does not cause a net decrease in the number of comets that pass through the inner Solar System, as its gravity perturbs their orbits inward roughly as often as it accretes or ejects them. This topic remains controversial among scientists, as some think it draws comets towards Earth from the Kuiper belt while others think that Jupiter protects Earth from the alleged Oort cloud. Jupiter experiences about 200 times more asteroid and comet impacts than Earth.A 1997 survey of early astronomical records and drawings suggested that a certain dark surface feature discovered by astronomer Giovanni Cassini in 1690 may have been an impact scar. The survey initially produced eight more candidate sites as potential impact observations that he and others had recorded between 1664 and 1839. It was later determined, however, that these candidate sites had little or no possibility of being the results of the proposed impacts.More recent discoveries include the following:

paragraph_text: The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest eight are the planets, with the remainder being smaller objects, such as dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.

paragraph_text: The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being smaller objects, such as dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.

paragraph_text: In November 1980, the Voyager 1 probe visited the Saturn system. It sent back the first high-resolution images of the planet, its rings and satellites. Surface features of various moons were seen for the first time. Voyager 1 performed a close flyby of Titan, increasing knowledge of the atmosphere of the moon. It proved that Titan's atmosphere is impenetrable in visible wavelengths; therefore no surface details were seen. The flyby changed the spacecraft's trajectory out from the plane of the Solar System.Almost a year later, in August 1981, Voyager 2 continued the study of the Saturn system. More close-up images of Saturn's moons were acquired, as well as evidence of changes in the atmosphere and the rings. Unfortunately, during the flyby, the probe's turnable camera platform stuck for a couple of days and some planned imaging was lost. Saturn's gravity was used to direct the spacecraft's trajectory towards Uranus.The probes discovered and confirmed several new satellites orbiting near or within the planet's rings, as well as the small Maxwell Gap (a gap within the C Ring) and Keeler gap (a 42 km wide gap in the A Ring).

paragraph_text: Kepler-10, the star that hosts Kepler-10b, is located 560 light-years from our solar system in the Draco constellation. It is approximately the same size as the Sun, with an estimated age of 12 billion years. Planet Kepler-10b was the first planet to be discovered in the orbit of its star. For this, it was designated the star's "b" planet. The star, in turn, was named for the Kepler Mission, a NASA-led operation aimed at discovering terrestrial planets that transit, or cross in front of, their host stars with respect to Earth. The planet's discovery was announced to the public on January 10, 2011.

paragraph_text: PSR B1257+12 was discovered by the Polish astronomer Aleksander Wolszczan on 9 February 1990 using the Arecibo radio telescope. It is a millisecond pulsar, a kind of neutron star, with a rotation period of 6.22 milliseconds (9,650 rpm), and was found to have anomalies in the pulsation period, which led to investigations as to the cause of the irregular pulses. In 1992 Wolszczan and Dale Frail published a famous paper on the first confirmed discovery of planets outside our solar system. Using refined methods one more planet was found orbiting this pulsar in 1994.

paragraph_text: Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth - largest planet by diameter, the third-most - massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near - twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50 × 10 km). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.

paragraph_text: The Moon is an astronomical body that orbits planet Earth, being Earth's only permanent natural satellite. It is the fifth - largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). Following Jupiter's satellite Io, the Moon is second - densest satellite among those whose densities are known.

paragraph_text: From its discovery in 1846 until the subsequent discovery of Pluto in 1930, Neptune was the farthest known planet. When Pluto was discovered it was considered a planet, and Neptune thus became the penultimate known planet, except for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer to the Sun than Neptune. The discovery of the Kuiper belt in 1992 led many astronomers to debate whether Pluto should be considered a planet or as part of the Kuiper belt. In 2006, the International Astronomical Union defined the word "planet" for the first time, reclassifying Pluto as a "dwarf planet" and making Neptune once again the outermost known planet in the Solar System.

paragraph_text: Mars is the fourth planet from the Sun and the second - smallest planet in the Solar System after Mercury. In English, Mars carries a name of the Roman god of war, and is often referred to as the ``Red Planet ''because the reddish iron oxide prevalent on its surface gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

paragraph_text: In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing - by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense. Gravity assistance can be used to accelerate a spacecraft, that is, to increase or decrease its speed or redirect its path. The ``assist ''is provided by the motion of the gravitating body as it pulls on the spacecraft. The gravity assist maneuver was first used in 1959 when the Soviet probe Luna 3 photographed the far side of Earth's Moon and it was used by interplanetary probes from Mariner 10 onwards, including the two Voyager probes' notable flybys of Jupiter and Saturn.

paragraph_text: Evacuate Earth is a National Geographic Channel documentary that portrays the hypothetical scenario of humans evacuating the planet Earth before it is destroyed by a rogue neutron star. The documentary details the technical and social complications of building a generation ship to save humanity and other Earth organisms by relocating to a planet in another solar system.

paragraph_text: Since 1973 a number of automated spacecraft have visited Jupiter, most notably the Pioneer 10 space probe, the first spacecraft to get close enough to Jupiter to send back revelations about the properties and phenomena of the Solar System's largest planet. Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Entering a Hohmann transfer orbit from Earth to Jupiter from low Earth orbit requires a delta-v of 6.3 km/s which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit. Gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter, albeit at the cost of a significantly longer flight duration.

paragraph_text: The Tharsis Montes are three large shield volcanoes in the Tharsis region of the planet Mars. From north to south, the volcanoes are Ascraeus Mons, Pavonis Mons and Arsia Mons. Mons (plural "montes") is the Latin word for mountain; it is a descriptor term used in astrogeology for mountainous features in the Solar System.

paragraph_text: Another project involved constructing the Digital Orrery by Gerry Sussman and his MIT group in 1988. The group used a supercomputer to integrate the orbits of the outer planets over 845 million years (some 20 per cent of the age of the Solar System). In 1988, Sussman and Wisdom found data using the Orrery which revealed that Pluto's orbit shows signs of chaos, due in part to its peculiar resonance with Neptune.If Pluto's orbit is chaotic, then technically the whole Solar System is chaotic, because each body, even one as small as Pluto, affects the others to some extent through gravitational interactions.

paragraph_text: In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune's atmosphere has active and visible weather patterns. For example, at the time of the Voyager 2 flyby in 1989, the planet's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 kilometres per hour (580 m/s; 1,300 mph). Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C). Temperatures at the planet's centre are approximately 5,400 K (5,100 °C). Neptune has a faint and fragmented ring system (labelled "arcs"), which was first detected during the 1960s and confirmed by Voyager 2.

paragraph_text: Saturn Glacier () is a glacier lying in southeast Alexander Island, Antarctica. The glacier is 15 nautical miles (28 km) long and 6 nautical miles (11 km) wide, flowing southeast into the George VI Ice Shelf of George VI Sound north of Corner Cliffs. Although the glacier is not situated within Planet Heights, its name derives from the nearby mountain range (Planet Heights) along with many other glaciers named after planets of the Solar System.

paragraph_text: A Small Solar System Body (SSSB) is an object in the Solar System that is neither a planet, nor a dwarf planet, nor a natural satellite. The term was first defined in 2006 by the International Astronomical Union.

paragraph_text: Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining known 14 moons were located telescopically until the 20th century. The planet's distance from Earth gives it a very small apparent size, making it challenging to study with Earth-based telescopes. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989. The advent of Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar.

Question: What spacecraft used the gravitational pull of the planet mentioned in this sentence?
Answer: Voyager probes