With Pluto firmly in its rearview mirror, New Horizons is now hours away from reaching a milestone distance, in which the probe will be 50 times farther from the Sun than Earth. To commemorate the achievement, the spacecraft performed a task that had never been attempted before at the edge of the solar system.
At 10:42 a.m. AEST on Sunday, April 18, New Horizons will be 50 astronomical units (AU) from the Sun, in which 1 AU is the average distance of Earth to the Sun, or approximately 150 million kilometres.
As a milestone, this number is wholly arbitrary and pleasing to our base-10 sensibilities, but it represents a rare achievement: New Horizons now joins an elite group of spacecraft to have reached this distance, the others being Pioneers 10 and 11 and Voyagers 1 and 2. Of these, Voyager 1 is the farthest human-made object ever, currently at 152.5 AU from the Sun, or 22.9 billion km.
Launched on January 19, 2006, New Horizons is now nearly 7.5 billion km from Earth. At this distance, it takes light seven hours to reach Earth, which means it now takes 14 hours to transmit instructions to the probe and then receive a confirmation signal back on Earth. The probe is so far from home that its view of distant stars now appears different compared to ours.
NASA celebrated the achievement by pointing New Horizons’s camera at the spot in space where Voyager 1 is currently located.
“Never before has a spacecraft in the Kuiper Belt photographed the location of an even more distant spacecraft, now in interstellar space,” declared NASA in a statement. “Although Voyager 1 is far too faint to be seen directly in the image, its location is known precisely due to NASA’s radio tracking.”
Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Colorado, described it as a “hauntingly beautiful image,” and I’m inclined to agree. The photo reminds us that we’re in the early stages of becoming an interstellar species and that our reach into the cosmos gets deeper with each passing day.
Previous milestones in the New Horizons mission include its flybys of Jupiter in 2007 and Pluto in 2015, as well as an encounter with the weirdly shaped Arrokoth in 2019.
From here, the probe will continue to venture into the outer reaches of the solar system. The science phase of the mission is still very much ongoing, as the probe collects important data about solar wind and the space environment. NASA plans to upgrade New Horizons’s software later this year to boost its capabilities. The probe is expected to last until at least the late 2030s, after which time its nuclear battery will no longer sustain the interstellar vehicle.