The Sounds Of The InterStellar Space
As Voyager 1 recedes from the solar system, researchers are listening for interstellar music (plasma waves) to learn more about conditions outside the heliosphere.
Scifi movies are sometimes criticized when explosions in the void make noise. As the old saying goes, in space, no one can hear you scream. Without air there is no sound.
But if that's true, the sounds of interstellar space were heard by astronomers?
It turns out that space can make music - if you know how to listen.
Some plasma wave data was played for astronomers and The sounds were solid evidence that Voyager 1 had left the heliosphere.
The heliosphere is a vast bubble of magnetism that surrounds the sun and planets. It is, essentially, the sun's magnetic field inflated to enormous proportions by the solar wind. Inside the heliosphere is home. Outside lies interstellar space, the realm of the stars
For decades, researchers have been on the edge of their seats, waiting for the Voyager probes to leave. Ironically, it took almost a year to realize the breakthrough had occurred. The reason is due to the slow cadence of transmissions from the distant spacecraft. Data stored on old-fashioned tape recorders are played back at three to six month intervals. Then it takes more time to process the readings.
The thrill of discovery when some months-old data from the Plasma Wave Instrument reached his desk in the summer of 2013. The distant tones were conclusive: Voyager 1 had made the crossing.
Strictly speaking, the plasma wave instrument does not detect sound. Instead it senses waves of electrons in the ionized gas or plasma that Voyager travels through. No human ear could hear these plasma waves. Nevertheless, because they occur at audio frequencies, between a few hundred and a few thousand hertz, we can play the data through a loudspeaker and listen. The pitch and frequency tell us about the density of gas surrounding the spacecraft.
When Voyager 1 was inside the heliosphere, the tones were low, around 300 Hz, typical of plasma waves coursing through the rarified solar wind. Outside, the frequency jumped to a higher pitch, between 2 and 3 kHz, corresponding to denser gas in the interstellar medium.
So far, Voyager 1 has recorded two outbursts of interstellar plasma music--one in Oct-Nov. 2012 and a second in April-May 2013. Both were excited by bursts of solar activity.
We need solar events to trigger plasma oscillations.
The key players are CMEs, hot clouds of gas that blast into space when solar magnetic fields erupt. A typical CME takes 2 or 3 days to reach Earth, and a full year or more to reach Voyager. When a CME passes through the plasma, it excites oscillations akin to fingers strumming the strings on a guitar. Voyager's Plasma Wave Instrument listens - and learns.
We're in a totally unexplored region of space and expect some surprises out there.
In particular, plasma waves are not excited by solar storms. Shock fronts from outside the solar system could be rippling through the interstellar medium. If so, they would excite new plasma waves that Voyager 1 will encounter as it plunges ever deeper into the realm of the stars.
The next sounds from out there could be surprising indeed.
What Lies Inside The Jupiter
For four long centuries the gas giant's vast interior has remained hidden from view. JUNO probe, launched on August 5th, changed all that.
It's really hot inside Jupiter! No one knows exactly how hot, but scientists think it could be about 43,000°F (24,000°C) near Jupiter's center, or core.
Jupiter is made up almost entirely of hydrogen and helium. On the surface of Jupiter-and on Earth-those elements are gases. However inside Jupiter, hydrogen can be a liquid, or even a kind of metal.
These changes happen because of the tremendous temperatures and pressures found at the core.
What is pressure?
Have you ever gone swimming at the deep end of a pool? Did you notice that your ears started to hurt a little bit when you were under water? The deeper you dive, the more water there is on top of you. All of that water presses on your body-and that's pressure.
The same type of pressure happens in Jupiter's core. Under low pressure, particles of hydrogen and helium, called molecules, have lots of room to bounce around. This is when hydrogen and helium are gases.
However, the weight of all this hydrogen and helium is really heavy. This weight presses down toward the planet's core, creating high pressure. The molecules run out of room to bounce around, so instead, they slow down and crowd together. This creates a liquid.
How much pressure would you find at the center of Jupiter?
Imagine if you swam to the bottom of the Pacific Ocean. You would feel more than 16,000 pounds of force pressing down on every square inch of your body. That is approximately the weight of four cars!
The pressure at the center of Jupiter is much higher. At Jupiter's core, you would feel as much as 650 million pounds of pressure pressing down on every square inch of your body. That would be like having approximately 160,000 cars stacked up in every direction all over your body!
What lies at the very center of Jupiter?
At the moment, scientists aren't 100% sure. It may be that the planet has a solid core that is bigger than Earth. But some scientists think it could be more like a thick, boiling-hot soup.
JUNO mission is designed to find answers to such remaining questions about Jupiter. The spacecraft is orbiting the giant planet, swooping in for close-up looks to get more detailed information.
Juno has already made many new discoveries about Jupiter. Scientists hope that information from Juno will help us measure Jupiter's mass and figure out whether or not the giant planet's core is solid.
