Scientists from the Max Planck Institute for Radio Astronomy (MPIfR)
in Bonn, Germany, Cornell University, USA, and the University of
Cologne, Germany, have detected two of the most complex molecules yet
discovered in interstellar space: ethyl formate and n-propyl cyanide.
Their computational models of interstellar chemistry also indicate
that yet larger organic molecules may be present — including the
so-far elusive amino acids, which are essential for life.
The results will be presented at the European Week of Astronomy and
Space Science at the University of Hertfordshire on Tuesday 21st
April.
The IRAM 30 m telescope in Spain was used to detect emission from
molecules in the star-forming region Sagittarius B2, close to the
centre of our galaxy. The two new molecules were detected in a hot,
dense cloud of gas known as the “Large Molecule Heimat”, which
contains a luminous newly-formed star. Large, organic molecules of
many different sorts have been detected in this cloud in the past,
including alcohols, aldehydes, and acids. The new molecules ethyl
formate (C2H5OCHO) and n-propyl cyanide (C3H7CN) represent two
different classes of molecule — esters and alkyl cyanides — and they
are the most complex of their kind yet detected in interstellar space.
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
The researchers then used a computational model to understand the
“But,” says Robin Garrod, a researcher in astrochemistry at Cornell
Adds Garrod, “There is no apparent limit to the size of molecules that
Senior MPIfR team member Karl Menten thinks that this will happen in
The simplest amino acid, glycine (NH2CH2COOH), has been looked for in
Two new highly complex organic molecules detected in space. Pictured here is Ethyl formate (C2H5OCHO). Two new highly complex organic molecules detected in space. Pictured here is n-Propyl cyanide (C3H7CN). Images: Oliver Baum, University of Cologne.
Original Paper:
“Increased complexity in interstellar chemistry: detection and
Further Information:
Max Planck Institute for Radio Astronomy (MPIfR), Bonn, Germany.
Cologne Database for Molecular Spectroscopy
Reference list of all 150 molecules presently known in space:
Cornell University, Ithaca, USA.
Institut fuer Radioastronomie im Millimeterbereich (IRAM), Grenoble, France.
Atacama Large Millimeter Array (ALMA), Chile.
Science Contacts:
Dr. Robin Garrod
EWASS meeting press room telephone (20th – 23rd April only):
astronomical sources contain so many different molecules that their
“fingerprints” overlap, and are difficult to disentangle” says Arnaud
Belloche, scientist at the Max Planck institute and 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”
adds Holger Mueller, researcher at 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.
chemical processes that allow these and other molecules to form in
space. Chemical reactions can take place as the result of collisions
between gaseous particles; but there are also small grains of dust
suspended in the interstellar gas, and these grains can be used as
landing sites for atoms to meet and react, producing molecules. As a
result, the grains build up thick layers of ice, composed mainly of
water, but also containing a number of basic organic molecules like
methanol, the simplest alcohol.
University, “the really large molecules don’t seem to build up this
way, atom by atom.” Rather, 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. The computational models show
that these sections, or “functional groups”, can add together
efficiently, building up a molecular “chain” in a series of short
steps. The two newly-discovered molecules seem to be produced in this
way.
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.”
the near future: “What we are doing now is like searching for a needle
in a haystack. Future instruments like the Atacama Large Millimeter
Array will allow much more efficient studies to discover organic
interstellar molecules.” These may even include amino acids, which are
required for the production of proteins, and are therefore essential
to life on Earth.
the past, but has not been successfully detected. However, the size
and complexity of this molecule is matched by the two new molecules
discovered by the team (Astronomy & Astrophysics, in press).
chemical modeling of ethyl formate and n-propyl cyanide in Sgr B2(N)”
by A. Belloche, R. T. Garrod, H. S. P. Mueller, K. M. Menten, C.
Comito, and P. Schilke, Astronomy & Astrophysics (in press), [DOI:
10.1051/0004-6361/200811550]
European Week of Astronomy and Space Science, Hertfordshire, UK, April 20-23, 2009.
http://www.astro.uni-koeln.de/cdms/molecules.
Dr. Arnaud Belloche
Max Planck Institute for Radio Astronomy, Bonn, Germany
Tel.: +49 228 525-376
Fax: +49 228 525-435
E-mail: belloche@mpifr-bonn.mpg.de
Dept. of Astronomy, Cornell University, USA
Tel.: +1 607 255 8967
Fax: +1 607 255 5875
E-mail: rgarrod@astro.cornell.edu
+44 (0)1707 285530
+44 (0)1707 285640
+44 (0)1707 285781
+44 (0)1707 285587
EWASS home page: http://www.jenam2009.eu
