NASA's New Horizons detects an ultraviolet glow that appears to be coming at the end of the solar system, between the threshold of the sun and the galaxy.

Pending NASA's approval, New Horizons is traveling to an object in the remote part of the space known as the Kuiper Belt after its closest approach to Pluto in 2015. Aboard the spacecraft is a compact ultraviolet imaging telescope and spectrometer called Alice.

Alice is originally intended to provide data where analysis of Pluto's atmospheric conditions will be based from. However, as the telescope skimmed pass through the edge of the solar system, it detected a glowing light source that has been the subject of debates among experts for many years.

The Hydrogen Wall

The glowing ultraviolet light was first spotted 30 years ago by the Voyager spacecraft. The New Horizons, on the other hand, was able to scan the ultraviolet sky seven times from 2007 to 2017.

For the current study published in the Geophysical Research Letters on Aug. 7, a group of scientists made a 360 view of this ultraviolet glow using Alice. They concluded that hydrogen particles that piled up beyond the solar system were emanating the mysterious blaze. The radiance is produced when the pile of hydrogen particles is interacting with the solar winds.

The team theorized that hydrogen particles were being pushed in the space between planets when the sun emits its charged particles outward. The sun's rays, however, have a limited range in space.

At the location in space where the sun's light wanes, the hydrogen particles end up in a pile. This pile is referred to by experts as the hydrogen wall and believed to be where the mysterious ultraviolet lights were produced.

Still Unsolved

Randy Gladstone, one of the authors of the study, still welcomed the possibility that the ultraviolet lights were something else despite data from Alice and the Voyager complementing each other.

"We assume there's something extra out there, some extra source of brightness," Gladstone said.

With this, scientists said they will continue to study the glow maybe twice a year until the source becomes certain.

Alice, meanwhile, will travel closer and closer to the hydrogen wall at the solar system's end. Hopefully, it can reach the interstellar space by 2040.

The New Horizons

The mission, launched on Jan. 19, 2006, is aimed at providing humans the knowledge about the "other worlds" that can be found at the edge of the solar system. It swang past Jupiter in February 2007.

It already conducted a six-month-long reconnaissance flyby study of Pluto and its moons in 2015. It achieved its closest distance to Pluto on July 14, 2015.

If it gets approved by NASA, it will then be flying farther into the Kuiper Belt, which is at least a billion miles beyond Neptune's orbit.