NASA Spacecraft Detects a 'Hum' in Interstellar Space
2021-05-17
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1Scientists say NASA's most distant exploring spacecraft has recorded what they describe as 'humming' beyond our solar system.
2A new study suggests the continuous hum, detected by the Voyager 1 spacecraft, is caused by waves existing in interstellar space.
3Voyager 1 left our solar system eight years ago, crossing the border that divides our solar system from interstellar space.
4"Interstellar" means "between stars."
5Scientists say interstellar space begins where the sun's continual flow of material and its magnetic field stop.
6Researchers say instruments on Voyager 1 identified the waves as vibrations in small amounts of gas found in the near-emptiness of interstellar space.
7The vibrations are also known as plasma waves.
8The spacecraft detected the waves over several years at different radio frequencies.
9Results from Voyager 1's findings were recently published in a study appearing in Nature Astronomy.
10Astronomers believe the space that Voyager 1 is passing through -- known as the interstellar medium -- is filled with different kinds of waves, both big and small.
11Such waves can provide information about the density of the interstellar medium.
12The new research was led by Stella Ocker, a doctoral student at New York's Cornell University and a member of NASA's Voyager 1 team.
13She was able to make the discovery by examining data slowly sent back by Voyager 1 from about 23 billion kilometers away.
14Ocker told Reuters the newly identified plasma waves would be far too weak to be heard with the human ear.
15"If we could hear (the hum), it would sound like a single steady note, playing constantly but changing very slightly over time."
16When the plasma waves are changed to an audio signal, the tone of the sound changes, added James Cordes.
17He is an astronomy professor at Cornell University and the co-writer of the study.
18That sound is "a bit eerie," he said.
19NASA said in a statement the new discovery may be the first continuous measurement of the density of material in interstellar space.
20Ocker added: "This detection offers us a new way to measure the density of interstellar space and opens up a new pathway for us to explore the structure of the very nearby interstellar medium."
21In the past, Voyager 1 had detected more powerful wave movements in interstellar gas linked to flares from the sun.
22But the new study suggests that continuous vibrations unrelated to solar activity could be normal in interstellar space.
23The researchers said the findings provide evidence that there is more low-level activity in interstellar gas than scientists had thought.
24Ocker said her work can lead to a better understanding of how the interstellar medium interacts with solar wind, the continuous flow of charged particles released by the sun.
25It can also provide data about how the heliosphere -- a protective bubble for our solar system - is shaped and changed by interstellar conditions.
26Voyager 1 was launched in 1977 along with another NASA spacecraft, Voyager 2.
27Both spacecraft were designed to explore Jupiter and Saturn.
28Voyager 1 entered interstellar space in 2012 and is still actively collecting and sending data.
29In 2019, NASA reported that Voyager 2 had also discovered new details about interstellar space.
30The two Voyagers were expected to last only five years.
31Both long outlasted their operational lifetimes, but are expected to run out of power and go silent within five years.
32However, Cordes said new spacecraft are already being designed and developed with the goal of traveling even farther beyond our solar system.
33"That is the message I find appealing: our reach is expanding into interstellar space," he said.
34I'm Bryan Lynn.
1Scientists say NASA's most distant exploring spacecraft has recorded what they describe as 'humming' beyond our solar system. 2A new study suggests the continuous hum, detected by the Voyager 1 spacecraft, is caused by waves existing in interstellar space. Voyager 1 left our solar system eight years ago, crossing the border that divides our solar system from interstellar space. 3"Interstellar" means "between stars." Scientists say interstellar space begins where the sun's continual flow of material and its magnetic field stop. 4Researchers say instruments on Voyager 1 identified the waves as vibrations in small amounts of gas found in the near-emptiness of interstellar space. The vibrations are also known as plasma waves. The spacecraft detected the waves over several years at different radio frequencies. 5Results from Voyager 1's findings were recently published in a study appearing in Nature Astronomy. 6Astronomers believe the space that Voyager 1 is passing through -- known as the interstellar medium -- is filled with different kinds of waves, both big and small. Such waves can provide information about the density of the interstellar medium. 7The new research was led by Stella Ocker, a doctoral student at New York's Cornell University and a member of NASA's Voyager 1 team. She was able to make the discovery by examining data slowly sent back by Voyager 1 from about 23 billion kilometers away. 8Ocker told Reuters the newly identified plasma waves would be far too weak to be heard with the human ear. "If we could hear (the hum), it would sound like a single steady note, playing constantly but changing very slightly over time." 9When the plasma waves are changed to an audio signal, the tone of the sound changes, added James Cordes. He is an astronomy professor at Cornell University and the co-writer of the study. That sound is "a bit eerie," he said. 10NASA said in a statement the new discovery may be the first continuous measurement of the density of material in interstellar space. Ocker added: "This detection offers us a new way to measure the density of interstellar space and opens up a new pathway for us to explore the structure of the very nearby interstellar medium." 11In the past, Voyager 1 had detected more powerful wave movements in interstellar gas linked to flares from the sun. But the new study suggests that continuous vibrations unrelated to solar activity could be normal in interstellar space. 12The researchers said the findings provide evidence that there is more low-level activity in interstellar gas than scientists had thought. 13Ocker said her work can lead to a better understanding of how the interstellar medium interacts with solar wind, the continuous flow of charged particles released by the sun. It can also provide data about how the heliosphere -- a protective bubble for our solar system - is shaped and changed by interstellar conditions. 14Voyager 1 was launched in 1977 along with another NASA spacecraft, Voyager 2. Both spacecraft were designed to explore Jupiter and Saturn. Voyager 1 entered interstellar space in 2012 and is still actively collecting and sending data. 15In 2019, NASA reported that Voyager 2 had also discovered new details about interstellar space. 16The two Voyagers were expected to last only five years. Both long outlasted their operational lifetimes, but are expected to run out of power and go silent within five years. 17However, Cordes said new spacecraft are already being designed and developed with the goal of traveling even farther beyond our solar system. "That is the message I find appealing: our reach is expanding into interstellar space," he said. 18I'm Bryan Lynn. 19Bryan Lynn wrote this story for VOA Learning English, based on reports from the Cornell Chronicle, NASA, Reuters and Nature Astronomy. Mario Ritter, Jr. was the editor. 20We want to hear from you. Write to us in the Comments section, and visit our Facebook page. 21_______________________________________________________________ 22Words in This Story 23detect - v. to discover or notice something 24vibration - n. a continuous, quick, shaking movement 25frequency - n. the number of times a wave, especially of light, sound or radio wave, is produced within a particular period 26steady - adj. happening in a smooth, continuous way 27constant - adj. happening a lot or all the time 28tone - n. a sound with a definite pitch and vibration 29eerie - adj. strange in a mysterious way 30flare - n. a sudden increase in brightness 31bubble - n. an enclosed or isolate space