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Life's complex molecules may have their origins in space

Jenny Winder, News Writer
Sep 28, 2014, 15:02 UTC

Sen—Astronomers have detected radio waves emitted by a new organic molecule lurking in interstellar space. The discovery suggests that the complex molecules needed for life may have their origins deep in the Universe.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) international researchers from Cornell in the US, and the Max Planck Institute for Radio Astronomy and the University of Cologne in Germany, studied a giant gas cloud in interstellar space.

Hunting from a distance of 27,000 light years, the astronomers discovered the unusual carbon-based molecule, with a branched structure, contained within the gaseous star-forming region Sagittarius B2, a zone close to the Milky Way’s galactic centre and an area rich in complex interstellar organic molecules.

The molecule, known as iso-propyl cyanide, is a variant (isomer) of a molecule already known to be quite prevalent in space. Organic molecules usually found in these star-forming regions consist of a single “backbone” of carbon atoms arranged in a straight chain. But the carbon backbone upon which the molecule is built is "branched", making it the first interstellar detection of such a molecule.

This distinction is very significant, according to the researchers, because it suggests that branched carbon-chain molecules may be fairly abundant in the interstellar medium.

The "iso" version of the molecule is almost half as abundant as the normal form. "The enormous abundance of iso-propyl cyanide suggests that branched molecules may in fact be the rule, rather than the exception, in the interstellar medium," says Robin Garrod, an astrochemist at Cornell University.  

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Dust and molecules in the central region of our Galaxy. Image credit: MPIfR/A. Weiß (background image), University of Cologne/M. Koerber (molecular models), MPIfR/A. Belloche (montage)

This detection opens a new frontier in the complexity of molecules that can be formed in interstellar space and that might ultimately find their way to the surfaces of planets. Models of how these molecules form suggest they are produced either within or on thin veneers of ice that coat interstellar dust grains.

The branched carbon structure of isopropyl cyanide is a common feature in molecules that are needed for life—such as amino acids, which are the building blocks of proteins. This new discovery lends weight to the idea that biologically crucial molecules, like amino acids that are commonly found in meteorites, are produced early in the process of star formation—even before planets such as Earth are formed.

ALMA is an array of 66 sensitive radio telescopes that work together to form a gigantic “eye” peering into the cosmos. Using ALMA the group were able to conduct a full spectral survey of the chemical makeup of Sagittarius B2, to look for fingerprints of new interstellar molecules, with sensitivity and resolution 10 times greater than previous surveys. 

About 50 individual features for isopropyl cyanide (and 120 for normal-propyl cyanide, its straight-chain sister molecule) were identified in the ALMA spectrum of the Sagittarius B2 region. The two molecules, isopropyl cyanide and normal-propyl cyanide, are also the largest molecules yet detected in any star-forming region. 

“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 lead author of the paper, published in the journal Science, Arnaud Belloche of the Max Planck Institute for Radio Astronomy.