The U.S. government believes its New Horizons spacecraft has detected a "hydrogen wall' at the boundary of the solar system, reports Joseph Farah's G2 Bulletin.
Live Science describes it as "the place where our sun's bubble of solar wind ends and where a mass of interstellar matter too small to bust through that wind builds up, pressing inward."
A study concluded the findings of the New Horizons craft affirm data from the Voyager spacecraft 30 years ago.
"Both sets of data are best explained if the observed ultraviolet light is not only a result of the scattering of sunlight by hydrogen atoms within the solar system, but includes a substantial contribution from a distant source."
It continued, "This distant source could be the signature of a 'wall' of hydrogen, formed near where the interstellar wind encounters with solar wind, or could be more distant."
It said future observations will be attempted twice a year to follow up.
Live Science explained: "Our host star's powerful jets of matter and energy flow outward for a long stretch after leaving the sun – far beyond the orbit of Pluto. But at a certain point, they peter out, and their ability to push back the bits of dust and other matter – the thin, mysterious stuff floating within our galaxy's walls — wanes. A visible boundary forms. On one side are the last vestiges of solar wind. And on the other side, in the direction of the sun's movement through the galaxy, there's a buildup of interstellar matter, including hydrogen."
New Horizons, which flew past Pluto in 2015, was able to see "extra ultraviolet light – the kind the researchers would expect such a wall of galactic hydrogen to produce."
For the rest of this report, and more, please go to Joseph Farah's G2 Bulletin.