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April 28, 2009
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“Complex” organic molecules detected in space
April 22, 2009
Courtesy Max Planck Institute
for Radio Astronomy
and World Science staff
Scientists say they have detected two of the most complex molecules yet discovered in space. Their computer models also indicate still larger molecules may be
out there, including the so-far elusive amino acids, essential for life as we know it. Models of organic
molecules newly identified in space. Above: ethyl formate; below:
n-Propyl cyanide. Color code of the atomic constituents of both
molecules: hydrogen: white, carbon: grey, oxygen: red and nitrogen: blue.
(Images: Oliver Baum, U. of Cologne)
The findings from the Max Planck Institute for Radio Astronomy in Bonn, Germany, Cornell University in New York, and the University of Cologne, Germany, were presented April 21 at the European Week of Astronomy and Space Science at the University of Hertfordshire, U.K.
The researchers used the IRAM 30-meter telescope in Spain to detect light emissions from molecules in the star-forming region Sagittarius B2, near the center of our galaxy. The molecules were identified in a hot, dense gas cloud known as the Large Molecule
Heimat, which contains a luminous young star.
Other large, organic molecules—carbon-containing compounds typically found in life forms on Earth—have been found in this cloud, including types of alcohols, acids and members of a group known as aldehydes. The new molecules, ethyl formate and n-propyl cyanide, represent different classes of molecule, called esters and alkyl cyanides.
Atoms and molecules are recognizable by light they emit at specific frequencies, or colors, on the light spectrum. Recognizing the signature of a molecule in the spectrum is rather like identifying a 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 of the Max Planck institute, first author of the research paper.
“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,” added Holger Muller of the University of Cologne. Out of
3,700 spectral lines detected with the IRAM telescope, the team identified 36
from the two new molecules.
The researchers then used a computer model to study the chemical processes that let these and other molecules form in space. Chemical reactions
result from collisions among gaseous particles; but there are also small grains of dust in the gas floating between stars. These grains can serve as landing sites for atoms to meet and react, producing molecules. As a result, the grains build up layers of ice containing basic organic molecules like methanol, the simplest alcohol.
“But,” said Robin Garrod, an astrochemistry researcher at Cornell, “the really large molecules don’t seem to build up this way, atom by atom.” Rather, the computer models suggest these molecules form section by section, using molecules already on the dust as pre-made building blocks. The newfound molecules seem to be produced this way, he added. “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,” he went on.
Senior team member Karl Menten at the Planck Institute argues this will happen soon, as the requisite instruments are rapidly improving. Future discoveries may even include amino acids, which are required for the production of proteins, and are therefore essential to life on Earth. The simplest amino acid, glycine, is no more complex than the two newfound molecules, according to research team members, whose work is to appear in the journal
Astronomy & Astrophysics.
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Scientists say they have detected two of the most complex molecules yet discovered in space. Their computer models also indicate still larger molecules may be present, including the so-far elusive amino acids, essential for life as we know it. The findings from the Max Planck Institute for Radio Astronomy in Bonn, Germany, Cornell University in New York, and the University of Cologne, Germany, were presented April 21 at the European Week of Astronomy and Space Science at the University of Hertfordshire, U.K. The researchers used the IRAM 30 m telescope in Spain to detect light emissions from molecules in the star-forming region Sagittarius B2, near the center of our galaxy. The molecules were identified in a hot, dense gas cloud known as the Large Molecule Heimat, which contains a luminous young star. Other large, organic molecules—carbon-containing compounds typically found in life forms on Earth—have been found in this cloud, including types of alcohols, acids and members of a group known as aldehydes. The new molecules, ethyl formate and n-propyl cyanide, represent different classes of molecule, called esters and alkyl cyanides. Atoms and molecules are recognizable by light that they emit at specific frequencies, or colors, on the light spectrum. Recognizing the signature of a molecule in the 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 of the Max Planck institute, first author of the research paper. “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,” added Holger Muller of the University of Cologne. Out of 3700 spectral lines detected with the IRAM telescope, the team identified 36 lines belonging to the two new molecules. The researchers then used a computer model to study the chemical processes that let these and other molecules form in space. Chemical reactions can take place as the result of collisions between gaseous particles; but there are also small grains of dust in the gas floating between stars. These grains can serve as landing sites for atoms to meet and react, producing molecules. As a result, the grains build up layers of ice containing basic organic molecules like methanol, the simplest alcohol. “But,” said Robin Garrod, a researcher in astrochemistry at Cornell University, “the really large molecules don’t seem to build up this way, atom by atom.” Rather, the computer models suggest these molecules form section by section, using molecules already on the dust as pre-made building blocks. The newfound molecules seem to be produced this way, he added. “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,” he went on. Senior team member Karl Menten at the institute thinks that this will happen soon, as the requisite instruments are rapidly improving. Future discoveries may even include amino acids, which are required for the production of proteins, and are therefore essential to life on Earth. The simplest amino acid, glycine, is no more complex than the two newfound molecules, according to research team members, whose work is to appear in the journal Astronomy & Astrophysics.