In a groundbreaking find, NASA's Voyager 1 probe, now traveling more than 14 billion miles from Earth, picked up a strange, steady hum coming from interstellar space. Launched in 1977, the Voyager 1 has traveled to the outer edges of our solar system and even beyond, making it the farthest human-made object on Earth. Now, in its journey into the vast unknown, the probe picked up something that scientists were not anticipating—a faint, continuous hum.
What is the Cosmic Hum?
The Voyager 1 spacecraft recorded a low-frequency sound-a steady signal that does not come from any known sources like solar flares or galactic radiation. This hum, or "plasma wave emission," appears to be coming from the diffuse gas, or plasma, which fills the space between stars. Plasma is made of charged particles and can make waves much like sound waves when agitated. The cosmic hum that Voyager has detected is so faint that it has eluded detection for decades, but new sophisticated signal processing methods have allowed scientists to catch it.
How Voyager 1 Found the Hum
Voyager 1 entered interstellar space in 2012 when it crossed out of the heliosphere, a region of particles and magnetic fields emanating from the Sun. Although the heliosphere shields our solar system, interstellar space is filled with diverse charged particles and plasma waves. The Plasma Wave System aboard Voyager 1 is a monitor of wave patterns, and it was this system that picked up the faint yet continuous hum.
This is unlike the robust bursty plasma waves emitted from solar flares, yet this is a persistent background hum, weak in power, suggesting the presence of some kind of stable source of interstellar plasma waves whose origin until now is a mystery. Scientists believe that because its frequency and regularity have suggested that it can not be due to some transients cosmic event, instead of some persistent process occurring in deep space.
What Could Be Causing This Cosmic Hum?
The cause of this hum is unknown but scientists have some theories about what might be happening. One theory is that this hum is coming from the low-density plasma in the interstellar medium, which is exactly where Voyager is now venturing. It may have something to do with how cosmic rays, high energy particles from outside the solar system, interact with the interstellar gases, making the plasma vibrate at a constant rate.
An altogether different theoretical possibility is this might be some sort of ringing from supernovae so ancient the shockwaves left then have now been rippling through the universe for millennia. Maybe as these continue to course through the interstellar medium they also create waves faint and consistent enough for Voyager 1 to be detecting.
Other speculation is that this could be the influence of the interstellar space magnetic field and the Sun's own magnetic field, from which Voyager 1 is moving out but might still be impacted. Magnetic fields could indeed create a form of "cosmic symphony" where energy is released by the changes and alignments.
Why It's Groundbreaking
It tells astronomers the nature of interstellar space: the configuration of that plasma outside of the solar system and its behavior. Data returned by Voyager 1 could yield the first clear indication ever of how dense interstellar plasma is-this, to this point, has not been measurable directly.
As Voyager keeps on its way, scientists are looking forward to when the probe encounters regions of plasma with varying densities. Such regions will give them a chance to know the nature of the cosmic hum.
The hum might turn out to be a base "heartbeat" for interstellar space. Scientists would use it to map its structure and behavior on large scales.
What's Next for Voyager 1?
Voyager 1 has now exceeded more than 45 years in its journey; it uses nuclear power that is depleting by the minute. Even though it is still working, most of its systems have started to be switched off, saving it some energy for perhaps a while longer. Even so, so long as Voyager's instruments stay in operation, it shall send data back to Earth giving a window to space into interstellar space.
The discovery of the cosmic hum by Voyager 1 adds to
its legacy as one of the most incredible scientific missions by humanity. Even
when most of the probes launched by the early space era have retired or lost
their functionality, Voyager 1 is helping in understanding unknown regions of
space, perhaps opening up doors for future interstellar travel.
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