Noble gases can be quite solitary elements, usually existing by themselves unless in forced laboratory conditions. However, now, for the first time ever, a noble gas molecule has been found in space.

Noble gases include the elements helium, neon, argon, krypton, xenon, and the radioactive radon. These elements are typically non-reactive due to the full nature of their valence electron shells, meaning they're already satisfied with what they have, and see no need to share bonds with other atoms. Studying noble gas molecules usually requires laboratories and induced conditions, making the discovery of a noble gas molecule in free space even more exciting.

Scientists using the European Space Agency's Herschel Space Observatory's SPIRE instrument found the distinct argon hydride ions in the Crab Nebula, the relatively close remnants of a star that exploded one millennium ago. By measuring specific wavelengths, the astronomers stumbled upon the unique molecule by accident.

"We were really concentrating on studying the dust in the filaments with SPIRE, and out pops these two bright emission lines exactly where we see the dust shining," says Haley Gomez from Cardiff University's School of Physics and Astronomy. "The team had a hard time figuring out what these lines were from, as no-one had seen them before."

"Finding this kind of molecule allowed us to evaluate the type (or isotope) of argon we discovered in the Crab Nebula," Gomez added. "We now know that it is different from argon we see in rocks on the Earth. Future measurements will allow us to probe what exactly took place in the explosion 1,000 years ago."

You can read the full published study detailing the findings in the journal Science.