Voyager 1 Records the Mysterious Buzz of Interstellar Space

New York, Gatra.com- The interstellar plasma vibrates out there past the edges of the solar system. Forty-four years after launching from Earth, the Voyager 1 spacecraft detected a background “hum” of interstellar space for the first time. Live Science, 12/4. Voyager 1, launched in 1977, left the boundary of the solar system – known as the heliosphere – in 2012. The heliosphere is a space bubble influenced by the solar wind, a flow of charged particles emanating from the sun.

Since emerging from this bubble, Voyager 1 has periodically sent back measurements of the interstellar medium. Occasionally, the sun emits a burst of energy known as the release of coronal mass which disrupts this medium, causing plasma, or ionized gas, from interstellar space to vibrate. These vibrations are very useful, because they allow astronomers to measure the density of the plasma – the frequency of the waves going through the plasma can reveal how closely the gas molecules are ionized. Now, however, researchers have realized that Voyager 1 also sends back a much more subtle signal: the constant “buzzing” of interstellar plasma. These low-level vibrations are fainter, but more durable, than the oscillations that occur after the release of the coronal mass. According to the new study, published May 10 in the journal Nature Astronomy, the buzz lasts at least three years. That’s good news to get a better understanding of interstellar plasma. “Now, we don’t have to wait for coincidences to get a density measurement,” said study leader Stella Ocker, a doctoral student in astronomy at Cornell University. “We can now measure density almost continuously.” Voyager 1 is currently nearly 153 astronomical units from the sun. The astronomical unit is the distance between the sun and the earth (150 million km), so that means that the spacecraft studded with antennas is now 153 times the distance Earth is from the sun. The aircraft is one of a pair originally designed to fly near Jupiter, Saturn, Uranus and Neptune, taking advantage of the rare planetary alignment that allows Voyagers 1 and 2 to use each planet’s gravity to propel themselves onto the next, according to NASA. Jet Propulsion Laboratory. Both Voyager 1 and 2 are still transmitting from interstellar space (Voyager 2 made it through the heliosphere in 2018). Ocker and his colleagues combed through data from the past five years of Voyager 1 transmission to find the subtle hum of interstellar space. They were surprised to find that the vibrations occurred at a narrow frequency, unlike vibrations from coronal mass events, which tended to appear wider, Ocker told Live Science. Researchers don’t know exactly what causes the plasma vibrations low-key, but it may have something to do with the “jitter” of electrons in the medium because of its basic thermal properties, says Ocker. Having a way to measure plasma density along the Voyager 1 path is useful, as researchers want to learn more about the distribution of ionized gases outside the solar system. The heliosphere interacts with this interstellar environment, says Ocker, and how changes in the structure of the plasma can reveal the details of how the interstellar medium forms the heliosphere and vice versa. “We want to know more about how the interstellar medium and the solar wind interact with each other to create heliosphere bubbles around the planet,” said Ocker. “So the Voyager outside of this bubble measuring density continuously can tell us a lot more about how the plasma behaves outside the bubble and how the bubble changes over time.”

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Editor: Rohmat Haryadi

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