List of artificial objects leaving the Solar System

The red and green arrows indicate the positions of Voyager 1 and Pioneer 10 respectively at the end of 2008; the blue shell indicates the estimated size of the termination shock they have entered, whereas the grey torus shows the Kuiper belt. The yellow shell indicates one light-day distance from the Sun. Click on image for larger view and links to other scales.

Below is a list of artificial objects leaving the Solar System. All of these objects are space probes and their upper stages launched by NASA. It does not include those missions that went into orbit around planets, or into orbit around the Sun because they are not leaving the Solar System.

List

Planetary exploration probes

Although other probes were launched first, Voyager 1 was able to achieve a higher speed and has overtaken all others. Voyager 1 overtook Voyager 2 a few months after launch, on 19 December 1977.[3] It overtook Pioneer 11 some time in the late 1980s, and then Pioneer 10—becoming the probe farthest from Earth—on February 17, 1998.[4]

Voyager 2 is also moving faster than the probes launched before it, and thus overtook Pioneer 11 in 1997 and will overtake Pioneer 10 sometime in 2021.

New Horizons will also likely pass the Pioneer probes, but will need many years to do so. It will not overtake Pioneer 11 until ~2082 and will not overtake Pioneer 10 until ~2130. Barring some unforeseen gravity assist it will never overtake the Voyagers.

Boosters

Every planetary probe was placed into its escape orbit by a rocket booster. These rockets are themselves on nearly the same trajectory as the probes they launched. Because they cannot be actively guided, their trajectories are now different from the probes they launched (the probes were guided with small thrusters that allow course changes). However, in cases where the spacecraft acquired escape velocity because of a gravity assist, the boosters may not have a similar course and there is the remote possibility that they collided with something. Some objects in heliocentric orbit have been reidentified with a telescope, and so it can be confirmed that they are still there. The boosters on an escape trajectory are:

None of these objects are trackable (they have no power or radio antennae, spin uncontrollably, and are too small to be detected), and their exact positions are unknowable beyond their projected Solar System escape trajectories.

The third stage of Pioneer 11 is thought to be in solar orbit because its encounter with Jupiter would not have resulted in escape from the Solar System. Pioneer 11 gained the required velocity to escape the Solar System in its subsequent encounter with Saturn.[6]

The only objects to date to be launched directly into a solar escape trajectory were the New Horizons spacecraft, its third stage, and the two de-spin masses. The New Horizons Centaur (second) stage is not escaping; it is in a 2.83-year heliocentric (solar) orbit.[7]

The Pioneer 10 and 11, and Voyager 1 and 2 Centaur (second) stages are also in heliocentric orbits.[11][12]

In order to leave the Solar System, the probe needs to reach the escape velocity. After leaving Earth, the Sun's escape velocity is 42.1 km/s. In order to reach this speed, it is necessary to take advantage to the orbital speed of the Earth around the Sun, which is 29.78 km/s. By passing near a planet, a probe can gain extra speed.

Gallery

See also

References

External links

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