After the historic milestone of that August 25, 2012, in which for the first time a human-created artifact reached interstellar space, the Voyager 1 probe; and that its sister, Voyager 2, did the same on November 5, 2018, we now know that Voyager 2 has entered the interstellar medium, leaving behind the border of the solar system, and officially ceasing to be under its influence . After Voyager 1, it is the second human-made object to do so.
The news has been confirmed by researchers at the University of Iowa and has been published in two articles in the journal Nature Astronomy.
The Voyager 2 probe reached the limit of the solar system on November 5, 2018, exactly one year ago. Now, the probe has crossed this boundary and entered the interstellar medium (ISM), a region beyond the boundary of the bubble produced by the solar wind. This region could be defined as the space that separates the stars from each other.
And why do we know where the probe is located? The solar wind is characterized by being formed of a hot plasma and of lower density compared to the plasma of interstellar space, of colder plasma and of higher density.
Scientists have found that Voyager 2 has crossed this border by detecting the increase in plasma density that it has experienced throughout its journey, through an instrument that measures plasma waves. This density jump was similar to that experienced by Voyager 1 years ago.
How has this income been produced?
Voyager 2’s entry into the interstellar medium occurred at 119.7 astronomical units (AU), that is, almost 18 billion miles from the Sun. Voyager 1, meanwhile, entered the ISM at 122.6 AU.
The two spacecraft were launched within weeks of each other in 1977, with different mission objectives and trajectories through space. However, they crossed the heliopause (the magnetic border that separates the Sun, the planets of the solar system, and the solar wind from the rest of the galaxy) at practically the same distances from the Sun.
Beyond the milestone of Voyager 2’s journey, researchers have been able to find out more details about the composition of our own solar system at its outer limits.
The heliosphere appears symmetrical
One of the contributions of the Voyager 2 trip are very valuable clues about the structure of the heliosphere , the bubble, with a shape very similar to a windsock, created by the solar wind as it extends to the edge of the system. solar.
“We can deduce that the heliosphere is symmetric, at least at the two points where the Voyager spacecraft crossed,” says Bill Kurth, a research scientist at the University of Iowa and a co-author of the study. “This indicates that these two points on the surface are almost the same distance.”
Fluids form boundaries
“The old idea that the solar wind will gradually shrink as you move through interstellar space is simply not true,” in the words of Don Gurnett of Iowa, corresponding author of the study, published in the journal Nature Astronomy. “We showed with Voyager 2, and previously Voyager 1, that there is a different boundary . It’s amazing how fluids, including plasma, form boundaries.”
Gurnett himself was also the author of the 2013 study published in Science that confirmed that Voyager 1 had entered interstellar space.
Data from the Iowa instrument on Voyager 2 also provides information on the thickness of the outer region of the heliosphere , (what we might call its ‘evolution’) and the point where the solar wind accumulates against the approaching wind in the interstellar space, which Gurnett likens to the effect of a snowplow on a city street.
The Iowa researchers also claim that the heliosphere’s envelope is of varying thickness , the data shows, given that Voyager 1 sailed 10 AU farther than its twin to reach the heliopause. Interestingly, some thought Voyager 2 would make that crossover first, based on previously devised models of the heliosphere.
Where is Voyager 1 now?
The last measurement obtained from Voyager 1 recorded that the spacecraft was 146 AU, or more than 13.5 billion miles from the Sun. The plasma wave instrument is recording that the density of the plasma is increasing (by which we know that is moving away).
The two Voyagers will last longer than Earth. Right now they are in their own orbits around the galaxy for five billion years or more.
Although Voyager 2 is equipped with a gold disk with information about the human being, greetings in all languages, a coordinate map to find the Earth … Researchers say (sadly) that the probability that they will find something is almost zero.
“They may look a bit worn by then,” adds Gurnett, (with a smile, as described in the press release).
