The source of X-rays has been a mystery for many years. The DXL sounding rocket provided scientists with answers.

Researchers proposed three theories about the source of X-ray emissions. One is that X-rays are the background noise of the universe. Another is they are formed from the interaction of solar winds and gas pockets. There is also a theory stating that X-rays come from the Local Hot Bubble.

Knowing the source of X-rays is important for scientists to understand the early history of the neighboring stars and to facilitate the creation of better material models in the galaxy.  

The DXL sounding rocket was flown in Dec. 13, 2012 to observe X-rays beyond the Earth, without the atmosphere to block most of the rays. The data from the sounding rocket show that 40% of the X-rays comes from solar wind charge.

"We show that the X-ray contribution from the solar wind charge exchange is about 40 per cent in the galactic plane, and even less elsewhere," said Massimiliano Galeazzi, an astrophysicist at the University of Miami.

The rest of the X-rays come from the Local Hot Bubble, an area of hot interstellar material surrounding the solar system.

Although the sounding rocket confirmed the ideas of the origin of X-rays, there are new questions arising from the data gathered because the rocket picked up high-energy X-rays that are not from any known source.

NASA's Chandra X-ray Observatory has also detected X-ray emissions from Pluto, and it also baffled scientists because Pluto is cold and has no magnetic field. That means it lacks the natural mechanisms needed to emit X-rays.