Published: Wed, November 06, 2019
Sci-tech | By Patricia Wade

NASA probe provides insight on solar system’s border with interstellar space

NASA probe provides insight on solar system’s border with interstellar space

Voyager 1 visited and got gravity assists from Jupiter and Saturn before heading off toward the edge of the solar system. And, somewhat than falling off a cliff when the probe reached interstellar space, solar particles ongoing to strike Voyager 2's sensors for much more than 50 times following the transition.

We didn't actually know when Voyager 2 might follow suit - the heliosphere is a bit wobbly, and slightly changes shape all the time - but in October a year ago, it started picking up an increase in cosmic radiation, similar to that experienced by Voyager 1 in 2012.

Voyager 2's entry into the ISM occurred at 119.7 astronomical units (AU), or more than 11 billion miles from the sun. Voyager 2 pushed across the heliopause from the hot, lower-density plasma of the solar wind into the cool, higher-density plasma of interstellar space. In doing so, the probe crossed a boundary area called the "heliopause". "Our journey has expanded deeper and deeper into space". This was when scientists knew it had entered a different region in space.

Some had thought Voyager 2 would make that crossing into interstellar space first, based on models of the magnetic bubble.

The Sun's heliosphere is like a ship sailing through interstellar space.

It is only the second probe to have sailed beyond the heliosphere - the expansive region made of plasma and magnetic fields generated by the Sun. Astronomers expected the direction of the magnetic field would be very different between the two.

Scientists are still trying to understand the nature of interstellar space wind and how much of it can seep through the heliopause to reach planets in our solar system.

This graphic shows the position of NASA's Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. "It does not surprise me that a sharp boundary forms". Around there, sun powered breezes spill into space and interface with interstellar breezes. The twin tests are now speeding through a locale known as the "bow shock", where the plasma of interstellar space streams around the heliosphere, much like water streaming around the bow of a moving boat.

Scientists expected that the edge of the heliosphere, called the heliopause, can move as the Sun's activity changes, sort of like a lung expanding and contracting with breath. As they study other stars with exoplanets around them, what they learn now could be applied to other systems they discover.

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However, they crossed into the ISM at basically the similar distances from the Sun.

The solar wind - the unending flow of charged particles emanating from the outer atmosphere of the sun - creates an enormous protective bubble called the heliosphere that envelopes the solar system.

The fact that both Voyager 1 and 2, which launched in 1977 to explore planets in our solar system, were created to only last for five years and have reached 42 is a wonderfully exciting surprise, Stone said. "They are of their grasp orbits around the galaxy for 5 billion years or longer, and the probability of them working into something else is almost zero". This was more clearly confirmed by Voyager 2 spacecraft. "And the probability of them running into anything is nearly zero".

The two spacecraft are now more than 10 billion miles from Earth.

The thrusters on both spacecraft are also degrading.

"At that point", explained astronomer Ed Stone of Caltech, "the mission became the Voyager Interstellar Mission".

Voyager 1 exited close to the very front of the heliosphere, relative to the bubble's movement through space.

The scientists can still communicate with Voyager 2, even in interstellar space, but the data takes about 16.5 hours to travel back to Earth.

Both Voyager tests estimated changes in the power of grandiose beams as they crossed the heliopause, alongside the progress between attractive fields inside and outside the air pocket.

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