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Two of the most complex molecules ever found outside the solar system have been turned up by astronomers peering into Sagittarius B2 (Sgr B2), a massive, vigorous star-forming region near the heart of the Milky Way.
Arnaud Belloche, an astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues detected the spectral signature of ethyl formate (far left in image) and n-propyl cyanide (at right in image) in electromagnetic radiation from Sgr B2. Both are relatively large organic (carbon-based) molecules—ethyl formate (C2H5OCHO) has 11 atoms and n-propyl cyanide (n-C3H7CN) has 12. Only cyanodecapentayne (HC11N), discovered in 1997, boasts more atoms among known interstellar molecules with 13.
Belloche and his co-authors suspect that the organics formed piecemeal on dust grains in the interstellar medium from pre-made building blocks. The mechanism could produce even more complex molecules, such as the amino acids that form proteins on Earth, but the signatures of such organics have yet to be found.
The researchers used the IRAM 30-meter telescope on Pico Veleta in southern Spain, near the city of Granada, which detects emissions in the millimeter regime—short-wavelength radio waves. Their results were presented this week at the European Week of Astronomy and Space Science at the University of Hertfordshire in England and are in press at the journal Astronomy & Astrophysics.
Sgr B2 has been a gold mine of organic compounds—the authors report that most complex molecules so far turned up in interstellar space were first discovered in a hot, dense cloud in the region called the "Large Molecule Heimat," which is where the new research revealed ethyl formate and n-propyl cyanide.
In an interview with the Guardian, Belloche noted that ethyl formate is present in raspberries. The chemical "does happen to give raspberries their flavour," Belloche told the newspaper, "but there are many other molecules that are needed to make space raspberries." At the very least, perhaps ethyl formate makes space smell nice—according to the Occupational Safety and Health Administration, the chemical has "a pleasant, fruity odor."
Molecules (hydrogen: white; carbon: gray; oxygen: red; nitrogen: blue): Oliver Baum, University of Cologne
