By Rafi Letzter
There’s a “hydrogen wall” at the edge of our solar system, and NASA scientists think their New Horizons spacecraft can see it.
That hydrogen wall is the outer boundary of our home system, 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. 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.
And now NASA researchers are pretty sure that New Horizons, the probe that famously skimmed past Pluto in 2015, can see that boundary.
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