Crab Nebula Home to First Noble-gas Based Molecule Ever Seen in Space

Deep inside the Crab Nebula, researchers have discovered the first evidence ever of a noble gas-based compound in space.

A wallflower, argon is so reluctant to join with others that its name is the Greek word for "inactive." The element comes from the group known as noble gases, which includes helium and other similarly independent spirits.

However, according to a new study published in the journal Science, argon appears to have found a friend. Using the Herschel space observatory, researchers detected signs of of a molecule known as argon hydride in the nebula first noted by Chinese astronomers almost 1,000 years ago.

"At first, the discovery seemed bizarre," said lead researcher Michael Barlow from University College London. "With hot gas still expanding at high speeds after the explosion, a supernova remnant is a harsh, hostile environment, and one of the places where we least expected to find a noble-gas based molecule."

Apparently, this was exactly what argon needed to get out of its comfort zone, the researchers found.

"The strange thing is that it is the harsh conditions in a supernova remnant that seem to be responsible for some of the argon finding a partner with hydrogen," said Paul Goldsmith of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Argon hydride is created when argon ions react with hydrogen molecules, though the two are usually found in completely different parts of a nebula.

"But we soon realised that even in the Crab Nebula, there are places where the conditions are just right for a noble gas to react and combine with other elements," Barlow said.

For these and other reasons, the researchers note the study is as much about the nebula as it is about argon.

"This is not only the first detection of a noble-gas based molecule in space, but also a new perspective on the Crab Nebula," said Göran Pilbratt, Herschel project scientist at the European Space Agency. "Herschel has directly measured the argon isotope we expect to be produced via explosive nucleosynthesis in a core-collapse supernova, refining our understanding of the origin of this supernova remnant."