The oldest type of molecule in our universe has been detected in space, scientists have revealed, supporting theories of how the early chemistry of the universe developed after the Big Bang.
It is believed that the positively charged molecule known as helium hydride has played a major role in the early universe, forming when a helium atom shares its electrons with a hydrogen, or proton, nucleus. Not only is it thought to be the first molecular bond, and first chemical compound, to appear as the cooled universe after the Big Bang, but also paved the way for the formation of hydrogen molecules.
But while helium hydride has been produced in the laboratory for nearly a century, it has proven difficult to detect in space, despite predictions that it should be present in clouds of gas in which stars are born, as well as gas expelled by stars.
"Although [helium hydride] is of limited importance on Earth today, the chemistry of the universe began with that ion, "write the authors. "The lack of definitive evidence of its existence in interstellar space has been a dilemma for astronomy."
Now experts say they finally found the helium hydride in a small but bright 600-year-old planetary nebula about 3,000 light-years away in the constellation Cygnus. Although this helium hydride was formed by a process different from that of the primordial universe, the team claims that its presence reinforces theories about what was happening in the "dawn of chemistry", bringing a "decades-long search for a happy ending in late ".
Dr Jérôme Loreau, a helium hydride specialist at the Université Libre de Bruxelles, who was not involved in the study, said the results were exciting, noting that although large organic molecules have been found in space, much more helium hydride simple was difficult. to track.
"Another reason is that HeH + [helium hydride] is the first molecule to form in the universe, about 380,000 years after the big bang, at a time known as the time of recombination, "Loreau said, adding that the molecules that emerged as the universe grew colder to the formation of stars and galaxies. "So it's very exciting to have finally observed one of the building blocks of the molecular universe."
One difficulty in detecting helium hydride is that indicator signals based on the light it emits after being struck by electrons tend to be obscured by almost overlapping "signatures" of a different molecule composed of carbon and hydrogen, however new instruments have appeared. .
Writing in the journal Nature, the team reported that they made their discovery by examining a planetary nebula known as NGC 7027, in which layers of gas are being lost from its warm nucleus – a white dwarf.
The data was collected using an instrument aboard a mission known as Sofia, a joint project between NASA and the German Aerospace Center, in which a specially modified Boeing 747SP flies very high in the Earth's atmosphere to about 13,700 meters foot). ), carrying a 2.7 meter telescope and other instruments. At this point, the instruments are above the vast majority of Earth's water vapor, which would otherwise obscure the signals of other molecules.
Crucially, these instruments offer a very high resolution, allowing the light from the helium hydride to be differentiated from the signatures of other molecules at very similar wavelengths.
Prof Phillip Stancil, a helium hydride specialist at the University of Georgia, also said that the finding was exciting, but noted only a "signature" of helium hydride was detected, and two are generally needed to be sure.
But Rolf Güsten of the Max Planck Institute for Radio Astronomy in Bonn, Germany, and the lead author of the research, said the chance that the identification is wrong is insignificant, adding that the findings solve a longstanding puzzle.
"The lack of evidence for the very existence of a helium hydride in the local universe has called into question our understanding of chemistry in the early universe," he said. "The detection reported here solves these doubts."