On November 13, 2026, a human-made object will reach one light-day from Earth for the first time in history, marking a significant milestone in space exploration. But here's where it gets controversial: while this event is groundbreaking, it also highlights the vast distance and incredible speed of light, which has implications for our understanding of space travel and communication.
The object in question is Voyager 1, a spacecraft launched in 1977 that has been traveling ever since. At the time of writing, it is around 169.5 astronomical units (AU) from Earth, having become the first spacecraft to go beyond the heliosphere, cross the heliopause, and enter interstellar space. At its current position, it takes 23 hours, 29 minutes, and 27 seconds for signals from Earth to reach the spacecraft.
The journey to reach one light-day from Earth will take over a year, and when it does, it will be the distance that light can travel in a day. According to calculations from IFLScience's resident astronomer, Dr. Alfredo Carpineti, using data from NASA's Eyes on the Solar System, this will occur on November 13, 2026. After this date, the probe will not fall within 24 light-hours from Earth again, despite the Earth-to-Voyager distance changing as we orbit the Sun.
But the journey will be far from over. First, it will leave the Solar System, passing through the Oort cloud, before having at least one close encounter with another star, Gliese 445, in the foreseeable future. The Oort cloud, a vast region of undiscovered objects, marks the gravitational edge of the Solar System. Short-period comets may originate in the scattered disk, inner part of the Oort cloud, while long-period comets likely come from the spherical, outer portion of the Oort cloud.
At the lower range of estimates, the Oort cloud could begin around 1,000 AU from the Sun. If the Oort cloud does begin here, Voyager could reach it in just a few centuries. However, given the sheer scale of the cloud, it will be there for tens of thousands of years. NASA explains that much of interstellar space is actually inside our Solar System, and it will take about 300 years for Voyager 1 to reach the inner edge of the Oort Cloud and possibly about 30,000 years to fly beyond it.
Assuming that the Voyager probes make it through the cloud undamaged, they could go on relatively unscathed for many, many years beyond that. For a long time, Voyager will not be near any astronomical objects, drifting on its own through the cosmos, far from sources of heat and light. But in 40,000 years, it will get a brief close encounter with another star, coming closer to it than home.
The study concludes that the spacecraft will encounter stars within a given distance at approximately the same rate as the Sun does, which Bailer-Jones et al. inferred to be one star within 1 parsec every 50,000 years. This rate scales quadratically with encounter distance, and as the spacecraft are not leaving the Galaxy, it is inevitable that the spacecraft will pass much closer to some stars on longer timescales.
Despite the vast distances and long timescales, Voyager 1 will continue to drift through the cosmos, guided by NASA until it runs out of power, likely in the early 2030s. But its journey will be far from over, as it will continue to explore the universe and potentially encounter other stars and celestial objects.
