April 21, 2009
Two Complex Organic Molecules Discovered In Space
Scientists in the US and Germany have discovered two of the most complex molecules ever to be found in space, and their scientific models imply that even larger molecules, such as amino acids, may also exist.
Scientists from the Max Planck Institute for Radio Astronomy in Bonn, Germany, Cornell University in the US, and the University of Cologne in Germany have reported the discovery of ethyl formate and n-propyl cyanide in space.Using the IRAM 30 m telescope in Spain, the team discovered emissions from molecules in a hot dense cloud of gas known as the "Large Molecule Heimat" in the star-forming region Sagittarius B2.
The "Large Molecule Heimat" contains a newly formed star, and other large organic molecules - including alcohols, aldehydes and acids - have been previously found within the cloud.
Atoms and molecules emit radiation at very specific frequencies, which appear as characteristic "lines" in the electromagnetic spectrum of an astronomical source. Recognizing the signature of a molecule in that spectrum is rather like identifying a human fingerprint.
"The difficulty in searching for complex molecules is that the best astronomical sources contain so many different molecules that their 'fingerprints' overlap, and are difficult to disentangle," said Arnaud Belloche, from the Max Planck Institute for Radio Astronomy.
"Larger molecules are even more difficult to identify because their fingerprints are barely visible: their radiation is distributed over many more lines that are much weaker," said Holger Mueller, of the University of Cologne.
The IRAM telescope found 3,700 spectral lines, from which the team identified 36 lines belonging to the two new molecules.
Scientists used a computer model to reveal how these large molecules, as well as others, form in space.
While chemical reactions are happening in space as the result of collisions between gaseous particles, small grains of dust within the interstellar gas can be used as landing sites for atoms to produce molecules. These grains build up thick layers of ice, which contain some basic organic molecules.
"But the really large molecules don't seem to build up this way, atom by atom," said Robin Garrod, a researcher in astrochemistry at Cornell University.
Instead, the computational models suggest that the more complex molecules form section by section, using pre-formed building blocks that are provided by molecules, such as methanol, that are already present on the dust grains.
"There is no apparent limit to the size of molecules that can be formed by this process -- so there's good reason to expect even more complex organic molecules to be there, if we can detect them," said Garrod.
Scientists will present their findings at the European Week of Astronomy and Space Science at the University of Hertfordshire on Tuesday.
Image 1: The IRAM 30m Telescope at Pico Veleta in southern Spain. Observations with this telescope at millimeter wavelengths led to the detection of both molecules, ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN). Image: IRAM
Image 2: Ethyl formate (C2H5OCHO). Image: Oliver Baum, University of Cologne
Image 3: n-Propyl cyanide (C3H7CN). Image: Oliver Baum, University of Cologne
Color code of the atomic constituents of both molecules: hydrogen (H): white, carbon (C): grey, oxygen (O): red and nitrogen (N): blue.
On the Net:
- European Week of Astronomy & Space Science
- Max Planck Institute for Radio Astronomy
- Cornell University
- University of Cologne