Voyager 1 – one of two sister NASA spacecraft launched 44 years ago and now the furthest man-made object in space – is still running and zooming into infinity.
The craft has long passed the edge of the solar system through the heliopause – the solar system’s border with interstellar space – into the interstellar medium. Now its instruments have detected the constant hum of interstellar gas (plasma waves), according to research conducted by Cornell University and published in Nature astronomy.
Examining the data slowly returned from over 14 billion miles, Stella Koch Ocker, a PhD student in astronomy at Cornell, discovered the show. “It’s very weak and monotonous because it’s in a narrow frequency bandwidth,” Ocker said. “We are detecting the lingering faint hum of interstellar gas.”
This work allows scientists to understand how the interstellar medium interacts with the solar wind, Ocker said, and how the solar system’s protective heliosphere bubble is shaped and changed by the interstellar environment.
Launched in September 1977, the Voyager 1 spacecraft flew by Jupiter in 1979 and then Saturn in late 1980. Traveling at around 38,000 mph, Voyager 1 crossed the heliopause in August 2012.
After entering interstellar space, the spacecraft’s plasma wave system detected disturbances in the gas. But, between these eruptions – caused by our own boiling sun – researchers have found a constant and lingering signature produced by the tenuous near-vacuum of space.
“The interstellar medium is like calm or gentle rain,” said lead author James Cordes, professor of astronomy George Feldstein. “In the case of a solar explosion, it’s like detecting a burst of lightning in a thunderstorm, then it’s soft rain again.”
Ocker believes there is more low-level activity in interstellar gas than scientists previously thought, allowing researchers to track the spatial distribution of plasma – that is, when it is not disturbed by solar flares.
Cornell research scientist Shami Chatterjee explained how important continuous monitoring of the density of interstellar space is. “We never had the opportunity to evaluate it. Now we know that we don’t need a fortuitous event related to the sun to measure interstellar plasma,” Chatterjee said. “Regardless of what the sun is doing, Voyager returns details. The craft says, ‘This is the density I’m swimming in right now. And here it is now. And here it is now. And here it is now. And here it is. now. ‘Traveling is far enough away and will do so continually. “
Voyager 1 left Earth with a gold disc created by a committee chaired by the late Cornell professor Carl Sagan, as well as mid-1970s technology. To send a signal to Earth, it took 22 watts, according to NASA’s Jet Propulsion Laboratory. The craft has nearly 70 kilobytes of computer memory and – at the start of the mission – a data rate of 21 kilobits per second.
Due to the distance of 14 billion miles, the communication rate has since slowed to 160 bits per second, or about half the rate of 300 baud.
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Material provided by Cornell University. Original written by Blaine Friedlander. Note: Content can be changed for style and length.