NASA have finally concluded, based on recent data, that the Voyager 1 spacecraft has indeed entered interstellar space.

There was a similar announcement from NASA last year when it was determined that at that point Voyager 1 had left the heliosphere--or the magnetic sphere that emanates from the sun. 

According to CBS News, researchers were able to conclude this latest feat by analyzing data received from Voyager indicating that a certain coronal mass ejection (CME) or solar eruption, had finally reached the spacecraft.

The CME, upon reaching Voyager, made the particles near the craft to oscillate rapidly enough for NASA scientists to determine the "density of the probe's surroundings," according to CBS. 

Apparently, a higher particle density informed NASA that Voyager could no longer be within the heliosphere, and therefore had reached a previously unexplored region of space.

According to CBS, interstellar space (where Voyager is now thought to be) is "emptier than areas near Earth, but the solar system thins out dramatically near the heliosphere's edge."

The CME used to determine Voyager's new milestone occurred in March 2012 and reached the spacecraft in April of 2013. By combining this data with another smaller CME from 2012, scientists calculated that the probe had indeed reached interstellar space in August of 2012. 

A third CME observed this past March provided further confirmation of these findings, which NASA announced this Monday. 

Although, the probe has reached interstellar space, there is some disagreement as to whether it is still within our solar system. This has to do with what is known as the Oort Cloud--a large region beyond our solar system made up of comets.

No one really knows exactly how far from our planet the Oort Cloud is, though NASA predicts Voyager 1 will exit the Oort Cloud within 14,000 to 28,000 years. 

Voyager 1 launched in 1977, nearly two weeks after its sister craft, Voyager 2. The probes began a journey through our solar system and provided vital images and data about the outer planets and their moons, like Saturn, Jupiter, Uranus and Neptune. 

Voyager 2 is also still operational, though it is currently on a slightly different course than its twin and is supposed to also reach interstellar space, like Voyager 1, in a few years.