In the News this month... complex organic molecules spotted near the galactic centre
Astronomers using a telescope in Spain have detected two of the most complex molecules ever found in interstellar space in a region known as Sagittarius B2, close to the Galactic centre. While hydrogen accounts for approximately three quarters of the visible matter in the Universe, many heavier elements are also present. Under the right conditions, these elements can form bonds creating a variety of different molecules. Like atoms, molecules emit electromagnetic radiation at very specific frequencies, resulting in a characteristic fingerprint of lines in the spectrum of an astronomical object. Detecting complex molecules in space involves searching for these fingerprints and trying to disentangle overlapping lines from different molecules. So far, more than 150 different molecules have been detected either in the interstellar medium or around stars. These include various organic molecules, those containing carbon atoms, although those found to date are much simpler than the amino acids which are the building blocks of all life here on Earth. Astronomers studying the chemistry of the Sagittarius B2 region have previously found numerous different large molecules including alcohols, aldehydes and acids. The cloud itself is a hot, dense ball of gas around a luminous young star in a known star forming region located approximately 100 parsecs from the Galactic centre.
Two new highly complex organic molecules detected in space. Left: Ethyl formate (C2H5OCHO), Right: n-Propyl cyanide (C3H7CN). Colour code of the atomic constituents of both molecules: hydrogen (H): white, carbon (C): grey, oxygen (O): red and nitrogen (N): blue. CREDIT: Oliver Baum, University of Cologne
The new study, led by Arnaud Belloche at the Max Planck Institute for Radio Astronomy in Germany and published in the journal Astronomy and Astrophysics, used the IRAM 30m telescope on Pico Veleta in Spain to obtain sensitive spectra of the region. When the team analysed their data, they discovered the spectral signatures of ethyl formate and n-propyl cyanide, two of the most complex molecules discovered in space so far. Some chemicals form by the collision of particles in a gas cloud, but astrochemical models suggest that more complex molecules form on small dust grains from individual atoms and simple molecules reacting together. Larger, more complex molecules are then formed by the addition of further simple molecules to the chain.
While the simplest amino acids, glycine, has not yet been detected in space, its size and complexity is similar to ethyl formate and n-propyl cyanide, suggesting that future surveys with more sensitive instruments could detect amino acids.