After making a careful analysis of the data, scientists have confirmed it: like Voyager 1 before it, the little space probe is now out beyond the heliopause, and heading deeper into the vast unknown of interstellar space.
Voyager 2, with all of its functionality still intact has been more successful in this regard and has rewarded researchers with a slew of much anticipated information. Researchers still hope to better understand the farther depths of the interstellar medium, beyond regions where solar particles still leak out of the heliosphere. This could be due to Voyager 1 crossing during a solar maximum (activity is now at a low) or the craft itself might have crossed through on a less perpendicular trajectory that meant it ended up spending longer at the edge. When Voyager 2, the longest-running space mission, crossed that frontier more than 40 years after its launch it sent a faint signal from the other side that scientists have now decoded. Yet they crossed into the ISM at basically the same distances from the sun. Confirmation of its exit came a few months after the fact.
Voyager 2 comes equipped with five different science operating instruments. These include magnetic field sensor, two instruments to detect energetic particles in different energy ranges and two instruments for studying plasma, which is a gas composed of charged particles. That transition from inside to outside the bubble took less than 1 day, the project scientists said, just like with Voyager 1. The new Voyager 2 data, like the Voyager 1 data before it, shows how CMEs propagate past the heliopause and lower the amount of cosmic rays beyond the bubble. The new findings confirm that the leakiness of the heliopause, spotted in two very different parts of the heliosphere, is not a rare characteristic of the bubble, although there is still no real explanation for what's causing it.
According to Don Gurnett, the principal investigator on the plasma wave instrument aboard both Voyager 2 and Voyager 1, the spacecraft entered the interstellar medium at 119.7 astronomical units (AU), or more than 11 billion miles (17.7 billion km) from the sun. A similar process regularly occurs between the Earth and Sun's magnetic field, so it would be no surprise to find the same thing happening between the Sun's (magnetic) field and the interstellar field. There won't be another opportunity to take data on this region of space for a very long time-even if a new probe launched today, the edge of the solar system would lie decades away. But they had been expected to peter out well before the bubble's boundary. "We didn't know how large the bubble was, and we certainly didn't know that the spacecraft could live long enough to reach the edge of the bubble and leave the bubble and enter interstellar space, at least nearby interstellar space".
Voyager 1 and 2 have now both passed through the heliosphere. Voyager 2, on the other hand, is located closer to the flank, and this region appears to be more porous than the region where Voyager 1 is located. "The speed of the plasma was essentially zero", Krimigis said. "And that remains a puzzle". In doing so, it joins Voyager 1 - the only object to reach this far out into the universe. "So, it's a puzzle".
The Voyager probes launched in 1977, each equipped with an identical suite of instruments for exploring the outer solar system. The findings were published Monday in a series of five papers in Nature Astronomy. Rankin is a space physicist at Princeton University in Princeton, N.J., who was not involved with the research.
With Voyager 1, scientists had only one sample of these magnetic fields and couldn't say for sure whether the apparent alignment was characteristic of the entire exterior region or just a coincidence. The transition happened about a year ago in November 2018, and the changeover was roughly in-line with what scientists expected based on Voyager 1's indirect readings.
"These observations, together with the Voyager 1 observations and existing models, show that the magnetic barrier, the heliopause and the neighbouring very local interstellar medium form a complex interconnected dynamical system", writes Leonard Bulgara at NASA Goddard Space Flight Center and colleagues in another paper submitted to Nature.