The New Horizons probe has just joined the very exclusive club of ships at least 50 Astronomical Units (AU) away from the Sun. Still active, the ship searches for its new target.
The American probe New Horizons has just passed the bar of 50 astronomical units separating it from our star. As a reminder, one astronomical unit is equivalent to the Earth-Sun distance. This therefore represents a journey of approximately 7.5 billion kilometers since its launch. At such a distance, it takes more than 6.5 hours so that the signals sent by the probe, currently in the Kuiper belt, reach the Earth at the speed of light.
Only four ships have traveled so many "cosmic landmarks". Launched in 1972, Pioneer 10 , which was the first probe to cross the asteroid belt and fly by Jupiter, crossed the 50 AU mark on September 22, 1990. It is currently sailing about 129 AU from Earth.
Launched in 1973, its twin, Pioneer 11 , reached 50 AU a year later in 1991. This craft was the first to make direct observations of Saturn. It now evolves about 105 AU from Earth.
Of course, don't forget the Voyager probes either. . Voyager 1 was launched on September 5, 1977, sixteen days after its twin Voyager 2. The first observed Jupiter and Saturn, while the second also observed Uranus and Neptune. Voyager 1 is 152 AU from Earth today and Voyager 2 is 127 AU. And, unlike Pioneer 10 and Pioneer 11, which ceased operations years ago, the two Voyager probes are still active today, now cruising through interstellar space.
More than just a milestone, reaching 50 AU also means New Horizons just exceeded its expected lifespan .
“One of the first things you do when designing a starship is to set requirements. And one of the things we had to define was the maximum distance that we could operate without too much trouble “, says Alan Stern, mission leader at the Southwest Research Institute in Boulder, Colorado. For New Horizons, this "goal line" was set at 50 AU. In other words, always active, the probe plays extensions.
New Horizons, which flew by Pluto in 2015 before making the most distant flyby in history (to date) on January 1, 2019, capturing the first close observations of A small Kuiper Belt ("Arrokoth") object at a distance of 43.4 AU from the Sun, therefore continues on its way and searches for new targets. The goal for the researchers will be to find it before the probe runs out of fuel.
Although it draws its electricity from a nuclear battery (a radioisotope thermoelectric generator, or RTG), the ship's plutonium power supply generates 33 watts less every decade . By the late 2030s, when New Horizons will be at or near 100 AU from the sun, it may no longer be powerful enough to function.
