Crossing the boundary into the space between the stars

Space · Published 25 October 2026 Swipe more like this →

In short: Our solar system is encased in a protective bubble of plasma called the heliosphere. To reach interstellar space, a spacecraft must travel beyond this boundary, entering the vast region between our Sun and the neighboring stars. It is a journey of immense scale, measured in billions of miles.

The area situated between the astrospheres of various stars and our Sun's heliosphere constitutes interstellar space. The heliosphere itself is a massive bubble of plasma—a gas of charged particles—generated by the solar wind, which spews out from the Sun. While the Sun circles the Milky Way galaxy's core, this sphere moves through the interstellar medium, producing a bow wave much like one made by a vessel's prow.

NASA's Voyager missions serve as our primary scouts in this frontier. Voyager 1 became the first human-made object to enter interstellar space on August 25, 2012, after a 35-year journey that began with its launch in 1977. It reached the boundary at a distance of about 122 Astronomical Units (AU) from the Sun, which is roughly 11 billion miles (18 billion kilometers). Voyager 2 followed a different path, touring Uranus and Neptune before taking 41 years to reach the same destination.

While these probes have successfully crossed the threshold, human travel to other stars remains science fiction. The distances are so vast that current technology requires generations of time to traverse the cosmic void. Furthermore, the Voyager probes are now operating on a strict power budget; their cameras were turned off in 1990 to preserve memory and power. Because the original ground computers that understand the camera software no longer exist, and the hardware has been exposed to extreme cold for decades, it is unlikely that the cameras could ever be reactivated.

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