Published: Sat, March 21, 2020
Sci-tech | By Patricia Wade

World Voyager 2 probe which launched 42 years ago reaches interstellar space

World Voyager 2 probe which launched 42 years ago reaches interstellar space

Now, scientists have shared the initial science gained by Voyager 2's historic crossing. By comparison, light traveling from the Sun takes about eight minutes to reach Earth. Each paper details the findings from one of Voyager 2's five instruments: a magnetic field sensor, two instruments to detect energetic particles in different energy ranges and two instruments for studying plasma.

It is an elusive boundary that marks the edge of the sun's realm and the start of interstellar space. Voyager 1, the faster of the two probes, is now over 13.6 billion miles (22 billion kilometers) from the Sun, while Voyager 2 is 11.3 billion miles (18.2 billion kilometers) from the Sun. The spacecraft recorded changes in the magnetic environment, the flows of solar and galactic particles, and different plasma temperatures that confirmed its entrance into interstellar space. The changes confirmed that the probe had entered a new region of space.

This information adds on to what Voyager 1, Voyager 2's twin spacecraft, has been observing since it's been in space on a similar mission.

It can be compared to a cosmic supertanker ploughing through space, said Edward Stone, a professor at the California Institute of Technology and lead author of one of five articles published in Nature Astronomy.

Stamatios Krimigis, a space scientist at the Johns Hopkins University Applied Physics Laboratory and the principal investigator of the mission's low-energy charged particles experiment, explained that the devices were created to last just four years, during which they would need to conduct 250,000 turns of a motor (dubbed "steps") to take measurements. Both the heliosphere and interstellar space are filled with plasma. This is the second interstellar spacecraft to reach so far from home, joining Voyager 1 which exited the solar system in 2012.

Artist impression of the solar system and interstellar space. Additionally, interstellar space contains cosmic rays, particles accelerated by exploding stars.

Voyager 1 passed through the heliosphere in 2012 but its crucial plasma instrument had been damaged during a fly-by with Saturn.

The findings suggest that the heliosphere is symmetrical, at least at the two points that the Voyager spacecraft crossed. Voyager 2 also sent out signals that hint that the plasma outside the heliosphere could be compressed as it is slightly warmer, though it is unclear what is causing the compression. "It's just astonishing how fluids, including plasmas, form boundaries".

It is not just the immediate surroundings which are of interest to scientists, but also what shape the heliopause is too. "Here we find a very hot plasma mass coming outward from the sun that encounters the cold plasma in the interstellar medium". As they study other stars with exoplanets around them, what they learn now could be applied to other systems they discover. This is considered the crossing point to interstellar space.

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That gives valuable clues to the structure of the heliosphere - the bubble, shaped much like a wind sock, created by the Sun's wind as it extends to the boundary of the solar system, the researchers said.

Voyager 1 had actually found signs of a leaky bubble as well. But they will continue on their trajectories long after they fall silent.

"The Voyager probes are showing us how our Sun interacts with the stuff that fills most of the space between stars in the Milky Way galaxy. And the probability of them running into anything is nearly zero".

The heliosphere is twelve billion miles from Earth.

The two probes will eventually cease to communicate over the next decade.

Over time, power system efficiency has decreased, and the generators produce 40% less than they did at the time of launch. Both spacecraft are traveling at more than 30,000 miles per hour (48,000 km/h). Engineers did the same thing with thrusters on Voyager 1 in 2017. According to this, Voyager-1 is the most man-made object from the earth. It's also using more power, so engineers turned off a heater for the Cosmic Ray Subsystem.

NASA's Voyager 2 spacecraft crossed into interstellar space last November. Now, there's a second spacecraft beyond the limits of our solar system: Voyager 2.

The data gathered by the probes has helped inform NASA's Interstellar Mapping and Acceleration Probe, scheduled to launch in 2024. A period of low solar activity should have pulled the heliopause back a bit during Voyager 2's crossing past year. This provides new insights into the thin external border of our space home.

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