The oldest molecule type was finally spotted in space

Helium hydride ions, considered the first type of molecule to form in the universe, were finally spotted in space.

These charged molecules, each composed of a neutral helium atom and a positively charged hydrogen atom, appeared for the first time about 100,000 years after the Big Bang. At the time, the universe was almost entirely composed of hydrogen and helium, and helium hydride was the only molecule that these two elements could create when of their collision.

Although researchers have seen helium hydride ions in the laboratory, these molecules have never been definitively detected in space. The discovery of helium hydride in a nearby planetary nebula puts an end to a search for these seminal molecules, which lasts for several decades, and helps to confirm our understanding of chemistry in the universe infant, report online researchers April 17 Nature.

During three flights in May 2016, the Stratospheric Airborne Observatory for Infrared Astronomy observed a planetary nebula called NGC 7027 at about 3,000 light-years apart. since. In the light emitted by the cloud of hot and dense gas, the researchers detected the wavelength of the infrared radiation characteristic of helium hydride.

The helium hydride ions observed in NGC 7027 were created in the planetary nebula, instead of being left by the primitive universe. But their existence confirms that helium hydride ions may exist outside the laboratory, which means that theoretical simulations of the primordial cosmos do not need to be seriously revised.

Adam Perry, who studied helium hydride at the University of Illinois, Urbana-Champaign, compares this discovery to the discovery of a fossil that constitutes a missing link in the animal evolution. "Everyone knew [helium hydride] had to be there, "says Perry, who did not participate in the study. But "where before there was no tangible evidence, now there are … People who are astrochimous are going to be very excited about that."

The study of helium hydride ions in NGC 7027 could offer new information about the chemical reactions that form these ions, says study co-author Rolf Güsten, an astrophysicist at the Max Planck Institute of Radio Astronomy Bonn, Germany.

Güsten and his colleagues also hope to use the Atacama Large Millimeter / Subillimeter Array, located in northern Chile, to explore the distant and early universe of helium hydride ions born shortly before. time after the Big Bang.