Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected two complex organic molecules – isopropanol (iC3HsevenOH) and its normal isomer, propanol (nC3HsevenOH) — in Sagittarius B2, a giant molecular cloud of gas and dust in the constellation Sagittarius.
“The detection of a branched alkyl molecule, isopropyl cyanide, in the interstellar medium with ALMA has opened a new window into the chemistry that takes place in star forming regions,” said Dr Arnaud. Belloche of the Max-Planck-Institut für Radioastronomie and his colleagues. .
“The production of such a branched molecule appears to require the addition of a functional group to a non-terminal carbon in the chain forming its backbone.”
“The detection was made as part of our previous imaging spectral line investigation called Exploring Molecular Complexity with ALMA (EMoCA) which targeted Sagittarius B2(N).”
“Since the discovery of isopropyl cyanide, many new complex organic molecules – which are carbon molecules containing at least six atoms by definition – have been reported in the interstellar medium, including two polycyclic aromatic hydrocarbons, but no other branched molecules n ‘was identified. “
Sagittarius B2 is located about 390 light years from the center of our Milky Way.
Also called Sgr B2, this huge stellar cloud has a mass of 3 million solar masses.
Its internal structure is complex, with varying densities and temperatures. It is divided into three main cores: north Sgr B2 (N), middle or main Sgr B2 (M) and south Sgr B2 (S).
In the new investigation, called Re-exploring Molecular Complexity with ALMA (ReMoCA), Dr. Belloche and his co-authors searched for isopropanol and its isomer in the hot core Sgr B2(N2).
They found that isopropanol is almost as abundant as normal propanol, with an abundance ratio of 0.6 which is similar to the ratio of 0.4 they had previously obtained for iso- and cyanide. normal-propyl with the EMoCA survey.
“The detection of normal propanol and isopropanol and their ratio indicate that the modest preference for the normal form of propyl cyanide previously determined may be a more general feature among interstellar molecules of similar size,” they said.
“Detecting other pairs of interstellar organic molecules with a functional group attached to a primary or secondary carbon can help pinpoint which processes dominate in defining their normal-to-iso ratios.”
“Butanol and its isomers would be the next obvious candidates in the alcohol family, but their detection in hot nuclei will be difficult.”
An article on the results has been published in the journal Astronomy & Astrophysics.
A.Belloche et al. 2022. Interstellar detection and chemical modeling of isopropanol and its normal isomer. A&A 662, A110; doi: 10.1051/0004-6361/202243575