Missing iron found in interstellar space
Astronomers find traces of a heavy element they have been hunting for years
Huge amounts of ‘missing’ iron, which astronomers have been looking for for decades, could be hiding in plain sight in the space between stars, according to a new study.
Iron is one of the most abundant heavy elements in the Universe and is commonly found around stars. However, when astronomers pull back to look at interstellar space, there seems to be hardly any.
This doesn’t necessarily mean that there is no iron in interstellar space, only that it’s in a form we can’t detect. The identity of this exotic form of iron has evaded astronomers for decades. Now, a team from Arizona State University (ASU) might have found the culprit – clumps of iron atoms bonded onto chains of carbon atoms known as iron pseudocarbynes.
“We are proposing a new class of molecules that are likely to be widespread in the interstellar medium,” said Pilarisetty Tarakeshwar, from ASU who led the study.
Astronomers know that clumps of iron atoms exist in space from looking at meteorites. Meanwhile, observations of interstellar space show that long chains of carbon atoms are found throughout the cosmos. The team discovered that in the deep freeze of space these two elements stick together, forming very different molecules than they would in the warm environment near a star.
“We calculated what the spectra of these molecules would actually look like, and we found that they have spectroscopic signatures nearly identical to carbon-chain molecules without any iron,” says Tarakeshwar.
The find could explain why the iron has gone unnoticed for so long – it blends into the background of these carbon chains. “Previous astrophysical observations could have overlooked these carbon-plusiron molecules,” says Tarakeshwar.
The discovery could also explain another long-standing puzzle. Despite the fact that any carbon chain over nine atoms long should be unstable and fall apart, astronomers regularly observe chains much longer than this limit. It could be that these long chains are created by iron atoms welding shorter chains together.
“Our work provides new insights into bridging the yawning gap between molecules containing nine or fewer carbon atoms and complex molecules such as C60 buckminsterfullerene, better known as buckyballs,” says ASU’s Frank Timmes. https://asunow.asu.edu