This could be due to Voyager 1 crossing during a solar maximum, as presently solar 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. Two spacecrafts had different paths: Voyager 2 didn't rush to the edge of Solar System, it explored Uranus and Neptune during planetary flybys first.
Now Voyager 2 has sent back the most detailed look yet at the edge of our solar system - despite Nasa scientists having no idea at the outset that it would survive to see this landmark.
Currently, Voyager 1 is located more than 22 billion kilometers (13.6 billion miles) from the Sun, and Voyager 2 is 18.2 billion kilometers (11.3 billion miles) from it.
Among many things, the astronomers are looking to gain a better understanding of how the solar winds - the stream of charge particles coming out of the sun - interact with the interstellar winds, made up of particles from other stars. Here are the five biggest takeaways. Voyager 1 left the solar system at a different location in 2012.
"Inside, the magnetic field comes from the Sun, carried out by the ionized solar wind, and outside the magnetic field is what is in the local region of the Milky Way galaxy", Stone said. He is also the principal investigator on the plasma wave instrument aboard Voyager 1 and authored the 2013 study published in Science that confirmed Voyager 1 had entered the ISM. Voyager 2 will pass red dwarf Ross 248 at a distance of 1.7 light years in around 40,000 years. The articles in Nature Astronomy now constitute the final confirmation of this and provide an initial scientific analysis of the measurement data collected by the probe. 2019. Cosmic ray measurements from Voyager 2 as it crossed into interstellar space.
"In a historical sense, the old idea that the solar wind will just be gradually whittled away as you go further into interstellar space is simply not true", The University of Iowa's Don Gurnett, who is one of the study authors, said in a statement. The marked increase in plasma density is evidence of Voyager 2 journeying from the hot, lower-density plasma characteristic of the solar wind to the cool, higher-density plasma of interstellar space.
Before Voyager 1 made the crossing to the other side, the data it sent back gave researchers at the time cause to think that the probe got caught up in two interstellar flux tubes; a kind of magnetic portal known as an interstellar flux transfer event. "It's just astonishing how fluids, including plasmas, form boundaries", Gurnett said. A period of low solar activity should have pulled the heliopause back a bit during Voyager 2's crossing previous year. Voyager 1 left the solar system when it had traveled 122.6 AU-almost 11.5 billion miles.
Voyager 2 also made some observations that don't square up with a sharp boundary-at least not what we'd expect.
The new papers now confirm that Voyager 2 is not yet in undisturbed interstellar space. When Voyager 1 crossed, "we were surprised to find that the direction of the magnetic field was not what we had expected when we were outside, and with Voyager 2 we are finding a very similar result".
When Voyager 2 crossed the boundary, it observed simultaneous increase in the intensity of cosmic rays, particles moving thought the space at almost the speed of light. And, interestingly, what Voyager 2's five instruments picked up shows a smoother, thinner heliopause, with a stronger magnetic field. Again, all this data taken together raises more questions than it can answer.
This bubble is called the heliosphere, and its boundary - where the outward pressure exerted by solar wind is no longer strong enough to push against the wind of interstellar space - is called the heliopause.
Unlike Voyager 1 however, Voyager 2 did not come across this phenomena, reports Edward Stone at the California Institute of Technology, Pasadena and co-authors.
A diagram describing the different parts of the heliosphere, the interstellar medium, and where the Voyager spacecrafts have travelled to. And as the spacecraft ventures even farther into interstellar space, communications are expected to suffer. The space between stars also contains cosmic rays, or particles accelerated by exploding stars.
Stone said the crafts' plutonium power sources will eventually stop supplying electricity, at which point their instruments and their transmitters will die.