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Voyager 1 detects plasma “hum” in interstellar space

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Voyager 1 instruments recently detected the low and constant “hum” of plasma in interstellar space. It’s a first. This work, signed by researchers at Cornell University, has been published in the journal Nature astronomy.

In interstellar space, far from the Kuiper belt, the American Voyager 1 probe has continued its journey for nearly forty-five years. The spaceship now operates more than twenty-two billion kilometers from our planet. And yet, we can still communicate with him.

A light rain between two thunderstorms

Examining the data slowly returned by the probe, Stella Koch Ocker, a doctoral student in astronomy at Cornell University, isolated a constant and persistent emission produced by the tenuous near-vacuum of interstellar space between two disturbances caused by solar flares. “This is a very low, monotonous hum, as it occurs in a narrow frequency bandwidth“, Specifies the astronomer.

This hum (3 kHz) is that of a plasma, a material so hot that the electrons have been torn from their atoms. The detection of this plasma alone is insignificant. After all, it is one of the most abundant forms of visible matter in the universe. Importantly, however, the probe had so far only detected strong plasma disturbances (oscillation events) triggered by coronal mass ejections from the Sun.

Here, Voyager 1 has recorded natural background plasma levels, or ambient, which are not influenced by our star.

Concretely, imagine the interstellar medium as a calm rain. In this environment, a solar explosion sometimes manages to slip as far from our star, acting like a thunderbolt in a thunderstorm. Then the rain comes back again. Voyager 1 has just detected the “sound” of this fine rain.

Credits: NASA, ESA and G. Bacon (STScI)

Towards a better understanding of the interstellar medium

This new work allows researchers to better understand how the interstellar medium interacts with the solar wind, and how the heliosphere’s protective bubble is shaped and modified by the interstellar environment.

Shami Chatterjee, co-author of this work, emphasizes how important continuous monitoring of the density of interstellar space is. “We had never had the opportunity to assess it. Now we know that we don’t have no need for a fortuitous event related to the sun to measure interstellar plasma“, Notes the astronomer. Thanks to Voyager 1, researchers will be able to follow the spatial distribution of plasma, even when it is not disturbed by solar flares.

This new detection is therefore very important for researchers, but remember that Voyager 1 and its Voyager 2 twin were not specially equipped to analyze this medium. The main objective of this program was indeed to collect scientific data on the outer planets of our system.

That’s why a NASA team board currently on the development of a new mission to probe this environment. The proposed probe would aim to collect data up to 1000 AU from the Sun.


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