NASA spots 'hydrogen wall' at edge of our solar system

NASA's New Horizons spacecraft has spotted a "hydrogen wall" at the edge of our solar system.
By Tyler MacDonald | Aug 14, 2018
NASA's New Horizons spacecraft has discovered an ultraviolet glow that appears to stem from the edge of the solar system. Researchers believe that it could be the long-sought "hydrogen wall" that marks the region where the sun's influence decreases.

"We're seeing the threshold between being in the solar neighborhood and being in the galaxy," said Leslie Young of the Southwest Research Institute, co-author of the study.

The sun creates a constant particle stream called solar wind as it makes its way through the galaxy. This wind creates a bubble called the heliosphere that surrounds our solar system.

Beyond the edge of this bubble, approximately 100 times farther from the sun than Earth, uncharged hydrogen atoms located in interstellar space are theorized to slow when they crash with solar wind particles. This build-up of hydrogen should create a unique scatter of ultraviolet light.

"It's really exciting if these data are able to distinguish the hydrogen wall," said space scientist David McComas of Princeton University, who was not involved in the study.

There is also the possibility that the origin of the extra light could be a source even further. But this will need to be confirmed by future studies.

NASA's New Horizons spacecraft will continue making twice-yearly measurements of the ultraviolet light until its mission comes to an end in the next 10 to 15 years. If researchers observe the light dimming, it could mean the hydrogen wall has been passed. But if it doesn't, it could mean that the source is further afield.

The findings were published in Geophysical Research Letters.

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