NASA’s Voyager 1 spacecraft will cross a historic threshold on November 18 when it becomes the first human-made object to reach one light-day from Earth. The milestone arrives at 5:16:07 AM Eastern Time, which translates to 3:46:07 PM in India. At that moment the probe will sit roughly 16 billion miles, or 26 billion kilometers, from home.
Launched in 1977 to study the outer planets, Voyager 1 has spent nearly 49 years traveling outward at about 38,000 miles per hour. It left the solar system’s boundary in 2012 and now sends data from interstellar space. A light-day represents the distance light covers in 24 hours, a scale that dwarfs familiar solar system distances — sunlight takes just over eight minutes to reach Earth, while light from Neptune needs about four hours.
Voyager 2, its twin launched the same year, followed a different path past Uranus and Neptune. NASA expects it to reach the same one light-day mark in November 2035, roughly 17 years behind its sibling.
Both craft carry golden records with sounds and images from Earth. Voyager 1 currently heads toward the star Gliese 445, also known as AC+79 3888, in the constellation Ursa Minor. That star lies more than 17 light-years away, and the probe will pass within 1.7 light-years of it in about 40,000 years.
The mission’s longevity continues to surprise engineers. Nearly five decades after launch, instruments still function and transmit findings from a region no other spacecraft has reached.
