Launched 44 years ago, the Voyager 1 probe since August 2012 is no longer flying in the heliosphere of the solar system. With the distance from the Sun, solar disturbances at different frequencies subsided, which allowed the apparatus to register a barely noticeable but steady “hum” of extremely rarefied ionized interstellar gas. Writes about this NASA.
Studying data from such distant places, scientists, due to the readings of the Plasma Wave System at the probe, revealed a very weak monotonic radio signal in a narrow frequency band. For clarity, it was translated into sound.
“We are detecting a faint, constant hum of interstellar gas,” they stressed.
Voyager 1 is the most distant man-made object and the first spacecraft to actually leave the solar system, although purely formally this is not the case: some scientists “set” the boundary of the solar system outside the hypothetical Oort Cloud at 50,000 – 100,000 AU. e. from the star. This is a collection of small space objects (comets, boulders, etc.), which is highly rarefied in space, which are still influenced by the gravity of the star. It will take Voyager 1 ~ 240 years to get to the inner edge of the OO, and up to 30,000 years to the outer edge. Voyager 1 is now at a distance of <153 AU. from the Sun, it is about 22.9 billion km.
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The authors of the study, published in the journal Nature Astronomy, compared the state of the interstellar medium near the “vague” inner boundary of the solar system with a light drizzle, the background noise of which is supplemented from time to time (during periods of disturbances on the Sun) “lightning strikes, after which everything calms down again.” …
Due to such grains of information from outside the heliosphere, scientists are gradually understanding how the interstellar medium interacts with radiation from the Sun, and how its “struggle” with it forms / changes the heliosphere bubble.
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The researchers believe that interstellar plasma has a higher level of background activity than previously thought. Below is the same background “hum” recorded over the years of observations:
Voyager 1 “hard disk” stores approximately 70 kilobytes of data. NASA uses the Deep Space Network’s ground-based radio telescope network to read the probe’s instrument data at a rate of ~ 160 bits per second. The radio signal travels from this distance for> 21 hours.