Nearly 100 times farther from the Sun than the Earth is, there’s a point where the charged particles from the Sun no longer reach into the uncharged particles of interstellar space, or the pockets of space that exist between the various star systems of the universe.
This point, known as a heliopause, marks the very edge of the solar system where human beings themselves live.
The heliopause border around the solar system was first “discovered” by scientists using NASA’s Voyager 1 and 2 spacecraft as far back as 30 years ago. But recently, a newer NASA spacecraft, the New Horizons space probe, has found actual evidence of that point in space.
The coolest part? The evidence comes in the form of a hydrogen “space wall,” made up of charged hydrogen particles that have built up at the edge of interstellar space.
According to Dr. Leslie Young, a scientist with the Southwest Research Institute in Colorado, this marks the edge of our solar system in a way she describes as almost similar to a fence around your property. “We’re seeing the threshold between being in the solar neighborhood and being in the galaxy,” Young explained, via Science News.
From 2007 through 2017, the New Horizons probe took measurements at the edge of the heliosphere using the Alice UV spectrometer.
Although it’s still a theory in progress, the data pulled by New Horizons suggests evidence that it found an ultraviolet glow known as a Lyman-alpha line, which exists at multiple points across the solar system but seems to exist in a wall form right along the heliopause.
How will the theory be further solidified? At some point, just as Voyager 1 and 2 did, New Horizons will pass the heliopause—and if the amount of ultraviolet light it picks up drastically drops off at that point, it will further provide evidence that the wall exists.
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