Spacecraft that have left or are about to leave the Solar System are depicted as square boxes
Trajectories of distant spacecraft from launch to 2030
Top: Polar view; Bottom: Equatorial view
Plot ofVoyager 2′s heliocentric velocity against its distance from the Sun, illustrating the use of gravity assist to accelerate the spacecraft by Jupiter, Saturn and Uranus, and finally its encounter with Neptune's Triton. Very massive planets attract spacecraft towards them, through the gravitational force; this force accelerates the spacecraft. If the spacecraft is not on a collision trajectory with the planet, and the spacecraft is travelling faster than the escape velocity of the planet, the spacecraft will travel past the planet gaining speed from the gravitational acceleration; this is called agravity assist (or “gravitational slingshot”).
Severalspace probes and theupper stages of their launch vehicles are leaving theSolar System, all of which were launched byNASA. Three of the probes,Voyager 1,Voyager 2, andNew Horizons, are still functioning and are regularly contacted by radio communication, whilePioneer 10 andPioneer 11 are now derelict. In addition to these spacecraft, some upper stages andde-spin weights are leaving the Solar System, assuming they continue on their trajectories.
These objects are leaving the Solar System because their velocity and direction are taking them away from the Sun, and at their distance from the Sun, its gravitational pull is not sufficient to pull these objects back or into orbit. They are not impervious to the gravitational pull of the Sun and are being slowed, but are still traveling in excess ofescape velocity to leave the Solar System and coast intointerstellar space.
Pioneer 10 – launched in 1972, flew pastJupiter in 1973 and is heading in the direction ofAldebaran (65 light years away) in the constellation ofTaurus. Contact was lost in January 2003, and it is estimated[as of?] to have passed 138astronomical units (AU; one AU is roughly the average distance between Earth and the Sun: 150 million kilometers (93 million miles)).[1]
Pioneer 11 – launched in 1973, flew past Jupiter in 1974 andSaturn in 1979. Contact was lost in November 1995, and it is estimated[as of?] to be at 116 AU.[2] The spacecraft is heading toward the constellation ofAquila, northwest of the constellation ofSagittarius. Barring any incident,Pioneer 11 will pass near one of the stars in the constellation in about four million years.[3]
Voyager 2 – launched in August 1977, flew past Jupiter in 1979, Saturn in 1981,Uranus in 1986, andNeptune in 1989. The probe left theheliosphere forinterstellar space at 119 AU on November 5, 2018.[4]Voyager 2 is still active. It is not heading toward any particular star, although in roughly 40,000 years it should pass 1.7 light-years from the starRoss 248.[5] Ross 248 and the Sun currently approach each other. In about 36,000 years they will fly past each other at a distance of under 3 light-years.[6] If undisturbed for296,000 years,Voyager 2 should pass by the starSirius at a distance of 4.3 light-years.[5]
Voyager 1 – launched in September 1977, flew past Jupiter in 1979 and Saturn in 1980, making a special close approach to Saturn's moonTitan. The probe passed theheliopause at 121 AU on August 25, 2012, to enterinterstellar space.[7]Voyager 1 is still active. In about 40,000 years the starGliese 445 (AC +79 3888) and the Sun will fly past each other at a distance of 3.45 light-years, after being currently 17.6 light-years from each other,[8] withVoyager 1 coming as close as 1.6 light-years to Gliese 445 at that time.[5][9]
New Horizons – launched in 2006, the probe flew past Jupiter in 2007 andPluto on July 14, 2015. It flew past theKuiper belt object486958 Arrokoth on January 1, 2019, as part of the Kuiper Belt Extended Mission (KEM).[10] On April 17, 2021, it reached a distance of 50 AU from the Sun.[11]
Although other probes were launched first,Voyager 1 has achieved a higher speed and overtaken all others.Voyager 1 overtookVoyager 2 a few months after launch, on December 19, 1977.[12] It overtookPioneer 11 in 1981,[13] and thenPioneer 10—becoming the probe farthest from the Sun—on February 17, 1998.[14]Voyager 2 is moving faster than all other probes launched before it; it overtookPioneer 11 in the late 1980s and thenPioneer 10 — becoming the second-farthest spacecraft from the Sun — in July 2023.[15]
Depending on how the "Pioneer anomaly" (heat radiating from the power source) affects it,New Horizons will also probably pass thePioneer probes, but will need many years to do so. It will overtakePioneer 11 in 2143, and will overtakePioneer 10 in 2314, but will never overtake theVoyagers.[13]
Note: Data above as of July 15, 2025. Source: JPL,[16] heavens-above.com,[17] and for New Horizons.[18]
Solarescape velocity is a function of distance (r) from the Sun's center, given by
where the productGMsun is the heliocentricgravitational parameter. The initial speed required to escape the Sun from its surface is 618 km/s (1,380,000 mph),[19] and drops down to 42.1 km/s (94,000 mph) at Earth's distance from the Sun (1AU), and 4.21 km/s (9,400 mph) at a distance of 100 AU.[20][21]
Voyager 1 and 2 speed and distance from the Sun
Pioneer 10 and 11 speed and distance from the Sun
New Horizons speed and distance from the Sun.
In order to leave the Solar System, the probe needs to reach the local escape velocity. Escape velocity from the sun without the influence of Earth is 42.1 km/s. In order to reach this speed, it is highly advantageous to use as a boost the orbital speed of the Earth around the Sun, which is 29.78 km/s. By later passing near a planet, a probe can gain extra speed from agravity assist.
A Star-48 rocket motor like the one used to launch theNew Horizons probe
Every planetary probe was placed into its escape trajectory by amultistage rocket, the last stage of which ends up on nearly the same trajectory as the probe it launched. Because these stages cannot be actively guided, their trajectories are now different from the probes they launched (the probes having been guided with small thrusters that allowed course changes). However, in cases where the spacecraft acquired escape velocity because of agravity assist, the stages may not have a similar course and there is the extremely remote possibility that they collided with something. The stages on an escape trajectory are:
Pioneer 10 third stage, a TE364-4 variant of theStar-37 solid fuel rocket.[22]
Voyager 1 fourth stage, a Star 37E solid fuel rocket.[23]
Voyager 2 fourth stage, a Star 37E solid fuel rocket.[23]
New Horizons third stage, aStar 48B solid fuel rocket, is on a similar escape trajectory out of the Solar System toNew Horizons, even arriving at Jupiter six hours beforeNew Horizons. On October 15, 2015, it passed Pluto's orbit at a distance of 213 million kilometers (over 1 AU) distant fromPluto.[24][25] This was four months afterNew Horizons' Pluto flyby.[26]
In addition, two smallyo-yo de-spin weights on wires were used to reduce the spin of theNew Horizons probe prior to its release from the third-stage rocket. Once the spin rate was lowered, these masses and the wires were released, and so are also on an escape trajectory out of the Solar System.[27][28]
None of the above objects are trackable – they have no power or radio antennas, spin uncontrollably, and are too small to be detected. Their exact positions are unknowable beyond their projected Solar System escape trajectories.
The third stage ofPioneer 11 is thought to be in solar orbit because its encounter with Jupiter would not have resulted in escape from the Solar System.[23][better source needed]Pioneer 11 gained the requiredvelocity to escape the Solar System in its subsequent encounter with Saturn.[dubious –discuss]
On January 19, 2006, theNew Horizons spacecraft to Pluto was launched directly into a solar-escape trajectory at 16.26 kilometers per second (58,536 km/h; 36,373 mph) from Cape Canaveral using anAtlas V and theCommon Core Booster,Centaur upper stage, andStar 48B third stage.[29]New Horizons passed the Moon's orbit in just nine hours.[30][31] The subsequent encounter with Jupiter only increased its velocity, and enabled the probe to arrive at Pluto three years earlier than without this encounter.
Thus the only objects to date to be launcheddirectly into a solar escape trajectory were theNew Horizons spacecraft, its third stage, and the two de-spin masses. TheNew HorizonsCentaur (second) stage is not escaping; it is in a 2.83-year heliocentric (solar) orbit.[24]
ThePioneer 10 and11, andVoyager 1 and2 Centaur (second) stages are also in heliocentric orbits.[28][32]
Voyager 1 and close encounters of the Sun with other stars in the next 100,000 years.
Given the huge emptiness of interstellar space, all the objects listed here are likely to continue into deep space in timelines that, barring the exceptionally unlikely chance of their colliding with (or being collected by) another object, could outlast even themain sequence existence of the Sun's life, billions of years hence.[33] One estimated timescale as to the likelihood of the Pioneer or Voyager spacecraft colliding with a star (or stellar remnant) is 1020 (100 quintillion) years.[34][35] They are very unlikely, however, to gain enough velocity to escape theMilky Way galaxy[34] (or itsfuture merger with the Andromeda galaxy) intointergalactic space.
In 1990, thesolar probeUlysses was launched towards Jupiter in order to reach a high-inclination heliocentric orbit over the Sun's poles; the spacecraft was shut down in 2008.Ulysses is currently in a 79° inclination orbit around the Sun with itsapoapsis crossing the orbit of Jupiter. In November 2098, it will have another close fly-by with Jupiter, crossing between the orbits ofEuropa andGanymede. After this slingshot maneuver, it will possibly enter ahyperbolic trajectory around the Sun and eventually leave the Solar System.[36]
Ulysses is now switched off as itsRTG power supply has run down, and so is uncontactable and cannot be tracked or guided in any way since 2009. Its exact trajectory is therefore unknowable as factors such as solarradiation pressure could significantly alter its encounter path.
