Unexpected metals have been found in comets that originated outside our solar system as well as within it, according to major new research.
Scientists found iron and nickel, which they referred to as a “big surprise”, inside the objects. The unexpected comets were found throughout our solar system, including far from our Sun – as well as in the comet 2I/Borisov, an interstellar object that began its life in another planetary system.
Such heavy metals are usually expected in hot environments, and it is the first time they have ever been discovered in the much colder atmospheres of distant comets, researchers say.
“It was a big surprise to detect iron and nickel atoms in the atmosphere of all the comets we have observed in the last two decades, about 20 of them, and even in ones far from the Sun in the cold space environment,” says Jean Manfroid from the University of Liège, Belgium, who led the new study.
And the fact they were found in objects that come from such different parts of the universe suggest there is some unknown affinity between our own solar system and whatever distant place the comet 2I/Borisov was formed in.
“If we can unravel the origin of nickel and iron in regular comets and this interstellar object, we might uncover a shared story of organic chemistry between different planetary systems,” scientists away from the study wrote in an accompanying article, published in Nature.
Comets can offer a look at solar systems in much earlier states, since they are made up of dust and ice from the time the planets were first forming. Researchers are able to explore them by looking at their coma – the trail that follows the comet – and inferring their composition.
Usually, metals are notably absent among those coma, because temperatures are not high enough. while they might be detected when they pass close to the Sun and get hot enough to let off nickel, they generally are made up of other substances.
Researchers who looked at 2l/Borisov when it was far from our Sun and still cold found, however, that it appeared to be emitting nickel. Rather than being released by heat, it may be being put out by photons, they suggest.
In a separate study, other scientists found the same surprising result when they looked at the comae from comets in our own solar system.
The two studies – one examining the interstellar comet and another looking at objects from our own solar system – are both published in Nature.
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