NASA Probe Detects Hydrogen Wall at the Edge of the Solar System

Representation of the hydrogen wall. (Image:  NASA)
Representation of the hydrogen wall. (Image: NASA)

NASA’s New Horizons spacecraft has detected what appears to be a wall of hydrogen at the edge of the solar system. The craft is en route to encounter a Kuiper Belt Object (KBO), Ultima Thule, in January 2019.

The wall

“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 the 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,” according to Live Science.

The two Voyager spacecraft, launched three decades ago by NASA, had reported signs of light scattering as they approached the edge of the solar system. Voyager 1 has since exited the heliosphere (the bubble around the solar system created by the Sun’s solar winds). Scientists theorized that the charged hydrogen atoms in interstellar space were colliding with solar wind particles, creating a hydrogen wall that scatters ultraviolet light. New Horizons is the first spacecraft in position to check on the Voyagers’ observations and confirm the light source.

The New Horizons space probe

The New Horizons space probe. (Image: NASA)

Despite discovering the hydrogen wall, the research team at NASA are also open to the possibility that the source of light might actually be something else. If ultraviolet light were to drop off at some point, then it will confirm that New Horizons has left the hydrogen wall. However, if the light never fades, then it would mean that the source is much further ahead than previously thought.

According to estimates, it will take about 10 more years to confirm the source of light. Fortunately, the instrument that detects ultraviolet light has enough juice to remain in operation for up to 20 more years. As such, New Horizons will continue scanning the sky for ultraviolet light two times a year.

The spacecraft mission

The New Horizons spacecraft was built jointly by the Southwest Research Institute (SwRI) and Johns Hopkins University Applied Physics Laboratory (APL). Launched as part of NASA’s New Frontiers program, the spacecraft set out into space in 2006 with a primary mission to do a flyby and study Pluto.  

Launched as part of NASA’s New Frontiers program, the spacecraft set out into space in 2006 with a primary mission to flyby and study Pluto. (Image: NASA)

Launched as part of NASA’s New Frontiers program, the spacecraft set out into space in 2006 with a primary mission to do a flyby and study Pluto. (Image: NASA)

After passing Jupiter, the spacecraft went in hibernation mode so as to preserve on-board systems. Only for annual checkups did the system come out of hibernation. In July 2015, New Horizons flew about 12,500 kilometers above Pluto, making it the first ever spacecraft to explore the small planet.

In August this year, NASA announced that New Horizons had confirmed the existence of the hydrogen wall at the outer edge of our solar system. Currently, New Horizons is following a mission extension to explore KBOs.

The spacecraft’s immediate mission is to perform a flyby of KBO (486958) 2014 MU69, also nicknamed Ultima Thule. The flyby is expected to take place on January 1, 2019. If everything proceeds as planned, Ultima Thule will be the farthest object in the solar system that has ever been visited by a spacecraft. Later on, New Horizons will continue making distant observations on at least two dozen more objects.

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