Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) group of radio telescopes have discovered a carbon-based molecule with a branched structure – a common feature in molecules that are required for life to form. Contained within a giant gas cloud in the star-forming region of Sagittarius B2, the molecule of isopropyl cyanide is the first hint that other complex molecules may form in space before finding their way to the surface of planets.

Located at a distance of approximately 27,000 light years from Earth, and close to our galactic center, Sagittarius B2 was observed by astronomers from Cornell University, the Max Planck Institute for Radio Astronomy and the University of Cologne using the ALMA telescopes to carry out a complete spectral survey designed to search for the tell-tale electromagnetic signatures of new interstellar molecules.

Conducting spectral analyses in the 84 to 111 GHz range, the on-going EMoCA (Exploring Molecular Complexity with ALMA) project under which this work was conducted is intended to interpret the molecular make up of Sagittarius B2 in order to test the results of prior astrochemical simulations and to advance knowledge on the chemical processes at play in the interstellar medium. In the course of this work, the team detected the new molecule in the northern hot core region of Sagittarius B2.

The molecule that they discovered there – isopropyl cyanide (i-C3H7CN) – is an isomer (a variant) of the straight-chained molecule normal-propyl cyanide (n-C3H7CN) already known to be relatively abundant in space. However, the carbon backbone of the isopropyl cyanide molecule is "branched" in this newest detection, identifying it as a precursor molecule essential for such things as amino acids which, in turn, are crucial elements for the building blocks of proteins and life.

"Understanding the production of organic material at the early stages of star formation is critical to piecing together the gradual progression from simple molecules to potentially life-bearing chemistry," said Doctor Arnaud Belloche of the Max Planck Institute for Radio Astronomy.

The ALMA telescope field has discovered a number of complex molecules over the years – including the likes of space “sugar” (glycolaldehyde), and water in one of the most distant galaxies ever recorded – but this new discovery may add much more weight to previous discoveries of amino acids arriving from space.

Working on the theory that amino acids found in meteorites that fell to earth in Sutter’s Mill, California, in 2012 indicated that precursor molecules may be found in interstellar space, the research team formulated the idea that biologically crucial molecules may be created early in the process of star formation – perhaps even before the planets formed.

Furthermore, the detection of the branched molecule in Sagittarius B2 in numbers similar to that of normal-propyl cyanide in other areas of space, leads the team to believe that star-forming areas such as Sagittarius B2 and the molecular composition of meteorites in which branched amino acids have been found, indicate that these regions may be the birthplace of the complex precursor molecules that eventually give rise to life.

The detection of the next member in this series of molecules, n-butyl cyanide (n-C4H9CN), and its three branched isomers in subsequent or future observations would greatly substantiate this hypothesis, and provide further evidence to the notion that complex organic molecules that lead to the eventual formation of life itself may well have begun in the interstellar dusts of space and not on planets like Earth, as previously thought.

The details of the research were published in the journal Nature.

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