New Horizons spots 'hydrogen wall' at edge of solar system

For the first time in history scientists believe they may be able to view the mysterious "hydrogen wall" that sits at the edge of our solar system.
By Joseph Scalise | Aug 14, 2018
For the first time in history astronomers believe they may be able to see the so-called "hydrogen wall" at the distant edge of our solar system, according to a newstudy in the journal Geophysical Research Letters.

The hydrogen wall is a boundary that sits at the edge of our home system. It is where the sun's bubble of solar wind ends and where a mass of interstellar matter that is too small to break through that wind builds up. That then creates a visible boundary that has the last remains of solar wind on one side and interstellar matter on the other.

While scientists have never been able to view the odd phenomenon before, they believe that is about to change.

New Horizons, the craft that moved past Pluto in 2015, is able to see extra ultraviolet light out at the space where the wall should be. In addition, it also appears to be the same light that NASA's probes first detected back in 1992.

While such observations are promising, they do not necessarily show that New Horizons can view the hydrogen wall. That is because the ultraviolet light detected by the probes could easily come from another source.

However, the team is still hopeful because Alice -- the instrument on board New Horizons that detected the light -- is much more sensitive than anything the Voyagers had on board.

"If the ultraviolet light drops off at some point, then New Horizons may have left the wall in its rearview mirror," wrote the researchers, according toLive Science."But if the light never fades, then its source could be farther ahead coming from somewhere deeper in space."

The finding holds a lot of promise. To follow up on it, New Horizons will scan the cosmos for ultraviolet light twice a year and then report any findings back down to Earth. If anything unusual pops up again, astronomers will instantly know.

"It's really exciting if these data are able to distinguish the hydrogen wall," said David McComas, a researcher at Princeton University who was not involved in the new work, in a statement.

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