CSIC scientists lead the detection of the largest molecules found in space

Oct. 16 () –

An international team led by Higher Council for Scientific Research (CSIC) has detected the largest molecules found so far in space. Specifically, it is two molecules consisting of 21 atoms each and that have been located in the cold interstellar cloud TMC-1.

The results, which are published in the journal ‘Astronomy & Astrophysics’provide new routes to understand the chemical complexity of the Universe.

Located in the constellation of Taurus, about 500 light years awaythe interstellar cloud TMC-1 (Taurus Molecular Cloud) is one of the closest to observing the formation of stars like the Sun.

This new discovery, in which it has been used the 40-meter radio telescope of the National Geographic Institute (IGN) at the Yebes Observatory (Guadalajara), It represents another step in understanding the chemical composition of this star-forming region.

Researchers have identified two cyanide compounds (organic molecules containing cyanide groups in their structure) derived from the polycyclic aromatic hydrocarbon (PAH) acenaphthylene (C12H8).

PAHs, whose structure is formed by carbon and hydrogen rings, are found naturally in substances such as coal or gasoline. It is considered that these molecules could be one of the pillars on which the origin of life in space would be based.

Careful analysis of the derived rotation constants (transitions between the rotational or spin energy levels of these molecules) has allowed scientists to focus on molecules larger than naphthalene (made up of 10 carbon and 8 hydrogen atoms), but smaller than anthracene and phenanthrene (consisting of 14 carbon and 10 hydrogen atoms, respectively, fused into three benzene rings).

The procedure they have used, based on detecting all the rotational lines of these molecules, guarantees unequivocal identification with respect to other techniques that use statistical methods.

“These results support a scenario in which PAHs grow in cold clouds from fused carbon rings of five and six carbon atoms and not just six, as previously believed.“, highlights José Cernicharo, CSIC researcher at the Institute of Fundamental Physics (IFF-CSIC).

Quantum chemistry calculations, the chemical synthesis of these molecules, as well as the spectroscopic study in the laboratory, support the molecular identifications of this team.

“In the spectrum, the molecules appeared to respond at frequencies of molecules with unpaired electrons, which we call radicals, but it was only in appearancethey only camouflaged themselves, which until now made their detection difficult,” says the IFF-CSIC researcher.

These conclusions are framed in the Don Quixote projectwhich aims to unravel the chemical complexity of a cold interstellar cloud, and which has provided the discovery of more than 90 molecular species in the last four years. One of the most notable results of this collaboration has been the discovery, using the standard line-by-line detection method, of a large amount of pure hydrocarbons with very high abundances.