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Post Info TOPIC: Polycyclic aromatic hydrocarbons
Blobrana


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Complex Organic Matter
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HKU Astronomers Discover Complex Organic Matter in the Universe

In today's issue of the journal Nature, astronomers report that organic compounds of unexpected complexity exist throughout the Universe. The results suggest that complex organic compounds are not the sole domain of life but can be made naturally by stars.
Prof. Sun Kwok and Dr. Yong Zhang of The University of Hong Kong show that an organic substance commonly found throughout the Universe contains a mixture of aromatic (ring-like) and aliphatic (chain-like) components. The compounds are so complex that their chemical structures resemble those of coal and petroleum. Since coal and oil are remnants of ancient life, this type of organic matter was thought to arise only from living organisms. The team's discovery suggests that complex organic compounds can be synthesized in space even when no life forms are present.
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Blobrana


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Anthracene
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An astronomical infrared study reveals one of the most complex organic molecules yet found in the interstellar medium - anthracene - offering possible new clues to the way the building blocks of life might have emerged.
Anthracene is a solid polycyclic aromatic hydrocarbon comprising a structure of three fused benzene rings in a row. Industrially, it can be produced from coal-tar or other residues of thermal pyrolysis and is commonly used as a starting material for dyestuffs, including the red dye alizarin. It is also used as an additive in wood preservatives, insecticides, and coating materials. Anthracene has no colour but does exhibit blue fluorescence with a peak at between 400 and 500 nanometres under ultraviolet light irradiation.
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Blobrana


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RE: Polycyclic aromatic hydrocarbons
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Title: A search for interstellar anthracene toward the Perseus anomalous microwave emission region
Authors: S. Iglesias-Groth, A. Manchado, R. Rebolo, J. I. Gonzalez Hernandez, D. A. Garcia-Hernandez, D.L. Lambert

We report the discovery of a new broad interstellar (or circumstellar) band at 7088.8 ± 2.0 \AA coincident to within the measurement uncertainties with the strongest band of the anthracene cation (C_{14}H_{10}+) as measured in gas-phase laboratory spectroscopy at low temperatures (Sukhorukov et al.2004). The band is detected in the line of sight of star Cernis 52, a likely member of the very young star cluster IC 348, and is probably associated with cold absorbing material in a intervening molecular cloud of the Perseus star forming region where various experiments have recently detected anomalous microwave emission. From the measured intensity and available oscillator strength we find a column density of N_{an+}= 1.1(±0.4) x 1013 cm-2 implying that ~0.008% of the carbon in the cloud could be in the form of C_{14}H_{10}+. A similar abundance has been recently claimed for the naphthalene cation (Iglesias-Groth et al. 2008) in this cloud. This is the first location outside the Solar System where specific PAHs are identified. We report observations of interstellar lines of CH and CH+ that support a rather high column density for these species and for molecular hydrogen. The strength ratio of the two prominent diffuse interstellar bands at 5780 and 5797 \AA suggests the presence of a "zeta" type cloud in the line of sight (consistent with steep far-UV extinction and high molecular content). The presence of PAH cations and other related hydrogenated carbon molecules which are likely to occur in this type of clouds reinforce the suggestion that electric dipole radiation from fast spinning PAHs is responsible of the anomalous microwave emission detected toward Perseus.

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Blobrana


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Online Database Of Molecular Spectra
A database 18 years in the works promises to help scientists sort out the astronomical role of a giant class of organic molecules that permeate stars and dust throughout the universe.
Developed by scientists at NASA's Ames Research Centre, in Mountain View, California, the database contains 600 theoretically and 60 experimentally determined infrared emission and absorption spectra of individual polycyclic aromatic hydrocarbons (PAHs).
PAHs are ubiquitous: They have been found in meteorites and may be precursors to prebiotic molecules, but they are also pervasive on Earth, often as pollutants.

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