NASA's Voyager 1 Probe Detects 'Gentle Rain' of Plasma Activity in Interstellar Space

Voyager 1—the first man-made object to enter interstellar space—continues to detect plasma waves in deep space despite being far, far away from our sun.

Scientists think that interstellar space, which is the unimaginably vast near-vacuum in between stars, is filled with interstellar plasma.

James Cordes, George Feldstein professor of astronomy at Cornell University, said in a statement that interstellar space is "like a quiet or gentle rain," and that the activity of our sun—a solar flare, for example—is like a lighting burst of plasma activity.

Meanwhile Stella Koch Ocker, a doctoral student in astronomy at Cornell, added there could be more low-level interstellar plasma activity than previously thought.

Ocker said: "We're detecting the faint, persistent hum of interstellar gas."

Voyager 1 was launched in September 1977 just a month after its sister probe, Voyager 2. Despite setting off slightly later, Voyager 1 is now further away from us than Voyager 2 as it is traveling at a speed of 38,000 mph compared to Voyager 2's 34,400 mph.

Both probes are now more than 10 billion miles away from us. Signals from Voyager 1 take around 21 hours to reach the Earth, despite traveling at the speed of light.

Voyagers 1 and 2 are both considered to be in interstellar space as they are outside of the sun's heliosphere—a region of space that is filled with the sun's magnetic field and solar wind.

The heliosphere extends far past the orbits of the planets until it reaches the heliopause—the boundary between itself and interstellar space. The distance from the sun to the heliopause is thought to be around 11 billion miles.

Voyager 1 crossed the heliopause in 2012 and Voyager 2 followed in 2018. As they crossed through this boundary, both probes observed an increase in galactic cosmic rays and a decrease in solar wind.

Ed Stone, a Voyager project scientist, said that most of the interstellar material outside of the heliosphere comes from exploded stars.

Voyager 1's detection of interstellar gas so far away from the Earth has been published in the journal Nature by Ocker and colleagues.

The study states that the exact mechanism behind the plasma detection could be clarified by further study using Voyager, or even with a future mission to interstellar space.

Shami Chatterjee, a Cornell research scientist, said: "Regardless of what the sun is doing, Voyager is sending back detail. The craft is saying, 'Here's the density I'm swimming through right now. And here it is now. And here it is now. And here it is now.' Voyager is quite distant and will be doing this continuously."

Voyager 1 contains the famed Golden Record—a circular plaque attached to the probe that contains coded messages about Earth's location in space, human culture, and some of what we know about the fundamental nature of the universe, just in case aliens find it.

Voyager 1
An artist's impression of the Voyager 1 probe traveling through space. The probe was launched in 1977. NASA/JPL-Caltech