Hear the spooky sounds of NASA’s Voyager galaxy


As NASA’s Voyager 1 explores the space of the galaxy, measurements of its density create waves

In the scattered group of atoms that fill the galaxy, Voyager 1 measured long-range sequential waves as only previously scattered explosions were detected.

Until recently, every spacecraft in history was making all of its measurements inside our heliosphere, the magnetic bubble that was excited by our sun. But on August 25 2012, NASAVoyager 1 changed that. As it crossed the boundaries of the heliosphere, it became the first human-made object to be measured – the galaxy. Now eight years into their galaxy, listening closely to the Voyager 1 data brings new insights into what those boundaries are.

If our heliosphere is a cruising galaxy, then Voyager 1 is a life raft dropped from the deck, which is designed to study currents. For now, almost any harsh water will come from the sun’s atmosphere. But from afar, you will feel the excitement coming from sources deep in the universe. Ultimately, the existence of the heliosphere will fade completely from his measurements.

Close to the Voyager 2 galaxy

This October 20218 graphic shows the state of the heliosphere-bound Voyager 1 and Voyager 2 probe, a protective bubble created by the sun, extending beyond Pluto’s orbit. Voyager 1 crossed the heliosphere or heliosphere in 2012. Voyager 2 remains on the solar panel, or the outer part of the heliosphere. (From NASA The Voyager 2 spacecraft entered galaxy space in November 2018Credit: NASA / JBL-Caltech

“We have some ideas about how long it takes Voyager to start seeing more pure galaxy water, so let’s talk,” said Stella Ocker, Ph.D. A student at Cornell University in Ithaca, New York and a new member of the Voyager team. But we do not know exactly when we will reach this level ».

The new OCR study was released on Monday Natural Astronomy, Which is the first continuous measurement of the density of an object in galactic space. “This discovery gives us a new way to measure the density of galactic space, and opens a whole new pathway to explore the structure of nearby galaxies,” said Oker.

NASA’s Voyager 1 spacecraft captured these sounds from the galaxy. Voyager 1s plasma The October instrument detects vibrations of dense galaxy plasma or ionized gas from November 2012 through April to May 2013. Credit: NASA /C.-Cultec

When one picks up interstellar objects – astronomers call it “the galactic medium”, massive particle soup and radiation – one can reconsider the calm, calm, and serene atmosphere. That would be a mistake.

“I used the phrase ‘interstellar medium’ – but you can find many places that are not particularly spacious,” said Jim Curtis, an astrophysicist at Cornell and co-author of the paper.

A galaxy is like an ocean, full of turbulent waves. The largest area of ​​our galaxy’s orbit, space smears itself, providing bases over tens of thousands of light years. Small (but massive) waves of supernova explosions erupt, stretching billions of miles from hills to hills. Usually very small waves come from our sun because solar flares send shock waves into space that penetrate the lining of the heliosphere.

These crashing waves reveal clues about the density of galactic media – a value that influences our understanding of the shape of the heliosphere, how stars form, and our position in the galaxy. When these waves echo in space, they vibrate the electrons around them, making sounds at distinct frequencies depending on how crowded they are together. The higher the ring tone, the higher the electron density. The Voyager 1 plasma wave subsystem – two “rabbit ear” antennas projecting 30 feet (10 meters) behind the spacecraft – is designed to hear this sound.

Voyager 2 instruments

Description of NASA’s Voyager spacecraft showing the antennas used by the plasma wave subsystem and other instruments. Credit: NASA / JBL-Caltech

In November 2012, three months after leaving the heosphere, Voyager 1 heard galaxies for the first time (see the video above). Six months later, another “whistle” appeared – this time louder and louder. The galaxy appeared thicker and faster.

These momentary sirens persist at random intervals in today’s Voyager data. It’s a great way to study the density of a galaxy, but it takes a little patience.

“It only appears once a year, so relying on these kinds of lucky events was a kind of dispersal of the galactic space density,” Oker said.

O’Keefe set out to find the running level of the galaxy’s mean density to fill in the gaps – not based on accidental shocks propagating from the Sun. After filtering the Voyager 1 data, while searching for weak but stable signals, it found a promising candidate. It began to rise in mid-2017, at the time of another whistle.

“It’s almost a tone,” Oker said. “Over time, we hear it change – but the way the frequency moves tells us how the density changes.”

Plasma oscillation events

Weak but nearly continuous plasma oscillation events – visible as a thin red line in this graphic / DK – incorporate strong events in the plasma wave subsystem data in Voyager 1. The image travels between maps showing only strong signals (blue background) and filtered data showing weak signals Just. Credit: NASA / JBL-Caltech / Stella Ocker

Oker calls the new plasma wave emission signal, which also appears to monitor the density of galactic space. When a sudden beep appears in the data, the emission tone rises and falls with it. The signal is similar to the one in Earth’s upper atmosphere, which monitors the electron density there.

“It’s very exciting because we can usually model the density over very long periods, which is the longest space we’ve ever had,” Oker said. “It gives us a complete map of the density that Voyager and the galaxy see.”

Based on the signal, the electron density around Voyager 1 began to rise in 2013 and reached its current levels in mid-2015, with an increase of about 40 times the density. The spacecraft also appears to be in a similar density range, with some fluctuations, through the entire dataset, which was completed in early 2020.

Ocker and colleagues are currently trying to develop a physical model of how the emission of plasma waves is produced, which will be important to explain. Meanwhile, Voyager 1’s plasma wave subsystem sends far and wide data back home, as each new invention has the power to re-visit our home in the universe.

To find out more about this research, in space 14 billion miles away, Voyager discovered an “Iohm” of plasma waves.

Note: Stella Koch Oker, James M. Curtis, Shami Chatterjee, Donald A. Gurnett, William S. Curt, Stephen R. Spankler, May 10, 2021 Natural Astronomy.
DOI: 10.1038 / s41550-021-01363-7

The Voyager spacecraft was built by NASA’s Jet Propulsion Laboratory, which continues to operate both. JBL is a division of the California Institute of Technology in Pasadena. The Voyager missions are part of NASA’s Solar Physics System Laboratory, which is provided by the Department of Solar Physics at the Science Mission Directorate in Washington.


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