New Horizons Views Hydrogen Wall Near Edge of Solar System

A massive wall of hydrogen gas has been spotted by astronomers surrounding the solar system. This wall marks the boundary where the solar wind streaming from our Sun becomes overwhelmed by the pressure from random material between the stars. At this point, a visible wall of hydrogen forms as the solar system travels through the galaxy. Researchers from NASA believe they have now seen this wall, in ultraviolet light, using the New Horizons spacecraft.

New Horizons was the first spacecraft to ever study Pluto. Now past that primary target, the robotic observatory is on a mission to explore the Kuiper Belt, a region of rocks orbiting the Sun, well past Pluto. On its journey there, the vehicle was expected to soar through a theoretical “hydrogen wall.”

“We’re seeing the threshold between being in the solar neighborhood and being in the galaxy,” said Leslie Young of the Southwest Research Institute.

New Horizons
The New Horizons spacecraft, seen flying past Pluto in this artist’s conception from NASA.

Earlier observations of this phenomenon were recorded by instruments onboard the Voyager spacecraft in 1992, and this latest observation confirms these earlier findings. A possibility remains that the ultraviolet light seen by the trio of spacecraft is the product of a phenomenon elsewhere in the galaxy. But, further observations by New Horizons should confirm or deny that possibility.

Prior to the arrival of New Horizons at Pluto, Earth-based astronomers knew of five moons surrounding Pluto. Among the prime group of researchers, all but one believed the spacecraft would discover new natural satellites in the system, but none were seen, surprising investigators.

New Horizons launched January 19, 2006, and arrived at Pluto July 14, 2015. Astronomers will continue to search for this wall twice a year, for as long as ALICE, and New Horizons, remains functional. The ALICE instrument aboard New Horizons is expected to last 15 to 20 more years.


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