“The interstellar medium is like a gentle rain,” says James Cordes, professor of astronomy at Cornell University in the USA. The “Sailor 1” space probe recorded a calm image of this rain to remain in the picture and sent the measurements to Earth.
A Stella Koch Oker research team evaluated the data and presented the results In “Nature Astronomy” magazine. “It’s a weak and monotonous signal in a very narrow frequency range,” says a PhD student at Cornell University. But it was used to absorb the quiet but steady hump of interstellar gas.
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Turbulence in interstellar space
Interstellar gas is distributed between the wires of the Milky Way. It is primarily hydrogen, which is partially ionized in the form of plasma. Interstellar gas and plasma clouds move along the rotation of the Milky Way.
In the interstellar space, into which the probe has penetrated, which can still be described as close to the sun, bursts of activity from the sun cause short-term disturbances. “When a sun comes out, it’s like seeing lightning in a thunderstorm,” Chords says. But then the soft rain starts again.
Die NASA-Probe Voyager 1 Had already sunk into the interstellar medium in 2012When it left the heliosphere. It is the name given to the place that the Sun fills with a continuous flow of particles known as solar wind. Since then, the probe has been recording measured values with its plasma wave system, which indicates the density of interstellar gas.
“These are low-frequency plasma waves that can be amplified by cosmic rays,” explains Hirong Yan of the University of Potsdam. The frequency is directly related to the density of plasma in the interstellar medium. By taking measurements along the flight path, Vyzer 1 was able to detect changes in density and turbulence outside the heliosphere. “The results seem to agree with previous understanding of interstellar turbulence,” says astrophysicists.
Solar system boundary
Previous studies of plasma density were based on shock waves, lightning strikes describing the cords, which propagate outward from the sun. Since 2017, Vyzer 1 has consistently sustained weak emission of plasma waves and recorded readings every 4.5 million kilometers along the flight path through approximately 4.5 billion kilometers of interstellar space.
The author states that how emissions are not clear and can be clarified with new findings from Vyzer 1 or with future interstellar missions. Since the intercepted signal is sustained, the Vyzer 1 can continue to track interstellar plasma density even without solar flares. The present work allows a better understanding of how the interstellar medium interacts with the solar wind, hence the ocher, and how the bubbles of the heliosphere are shaped and altered by the interstellar environment.
In shape, the heliosphere may resemble comets rotating through space with rotation of the Milky Way. However, it can also be spherical in shape and possibly contract and expand with decreasing and increasing solar activity.
When the Vyjar 1 and 2 spacecraft were launched in 1977, It was also not clear where the boundary of the heliosphere was. The sunburst of activity in 2012 caused the plasma through which Vyzer 1 emitted radio waves the following year, which the spacecraft picked up. Their frequency suggested that Vyzer 1 had entered interstellar space.