spaceSpace and Physics

Molecules of noble gases have been discovered in space

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Lisa Winter

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191 Molecules of noble gases have been discovered in space
NASA, ESA, J. Hester and A. Loll (Arizona State University)

Until now noble gases have only been found on Earth. They are usually found alone as they don’t readily react with other atoms. While studying the Crab Nebula, astronomers using the Herschel Space Observatory were able to observe molecules of argon hydride in space, which is the first noble gas molecule ever observed outside of Earth. The research was led by Professor Mike Barlow at University College London and were published in Science.

The noble gases represent group 18 of the periodic table. In order of increasing atomic mass, they include helium, neon, argon, krypton, xenon, and radon. Because their valence shell is full, they are inert. Under very precise circumstances, scientists can coerce them into reacting with other elements. Because of how specific the environment must be, noble gas molecules have not previously been observed in space and scientists assumed they could only exist on Earth. New research of the Crab Nebula has shown that it is possible for noble gas atoms to form molecules in space.


A group of astronomers have been using the Herschel Space Observatory to study the Crab Nebula. The nebula is only about 1000 years old and just over 6,500 light years away, making it very easy for scientists to learn about what happens when massive stars explode. The team has been analyzing the gas composition in order to better understand how large amounts of dust are created in these events.

As the gas molecules spin, researchers can use the color of the light being emitted in order to determine the composition. This wavelength is known as an emission line. One molecule completely stunned the researchers: argon hydride. This was the first time a noble gas molecule has been observed outside of a strictly managed laboratory setting. The best part? The monumental discovery happened on accident. The team had been interested in studying the dust filaments, but the argon hydride emission lines were right in the way. In an attempt to identify the gas in order to dismiss it and get back to the dust, the team made the amazing discovery.

The team has also determined how the molecule was formed. During the explosion, argon atoms became ionized. Shockwaves from the radiation fused the argon with molecular hydrogen, forming the molecule. They were also able to figure out that the argon in the Crab Nebula is not the same isotope of argon that we are use. 

This information provides very important clues that will help astronomers understand all of the circumstances surrounding the star’s explosion.


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