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TOPIC: Extended Red Emission

Blobrana

L

Posts: 131433

Date: Aug 2 21:15 2010

RE: Extended Red Emission	Permalink

NASA Reveals Key to Unlock Mysterious Red Glow in Space NASA scientists created a unique collection of polycyclic aromatic hydrocarbon (PAH) spectra to interpret mysterious emission from space. Because PAHs are a major product of combustion, remain in the environment, and are carcinogenic, the value of this PAH spectral collection extends far beyond NASA and astronomical applications. For years, scientists have been studying a mysterious infrared glow from the Milky Way and other galaxies, radiating from dusty regions in deep space. By duplicating the harsh conditions of space in their laboratories and computers, scientists have identified the mystifying infrared emitters as PAHs. PAHs are flat, chicken-wire shaped, nano-sized molecules that are very common on Earth. Read more __________________

Blobrana

L

Posts: 131433

Date: Apr 27 09:08 2007

Polycyclic aromatic hydrocarbons	Permalink

Astronomers may be one step closer to understanding how the ingredients of life are processed in space, thanks to NASA's Spitzer Space Telescope. On Earth, the elements carbon and hydrogen dominate the chemistry of all life. Because molecules called polycyclic aromatic hydrocarbons, or PAHs, contain both of these elements and are abundant all over the universe, many astronomers suspect that they may be among life's building blocks. PAHs are also especially hardy molecules -- typically found in hot, chaotic regions of space -- leading some to believe that they could have survived the harsh environments of the planet's early days. So, how do PAHs come to be? Astronomers may be one step closer to solving this mystery, now that a team of scientists led by Dr. Greg Sloan of Cornell University, Ithaca, N.Y., has detected many predecessors of PAHs in a relatively cool region of space. Read more __________________

Blobrana

L

Posts: 131433

Date: Apr 7 03:37 2007

Polycyclic aromatic hydrocarbon molecules	Permalink

NASA scientists have discovered evidence that a mysterious red glow, seen throughout the Milky Way and other galaxies but never on Earth, radiates from extremely fine dust clusters that cause the glow by combining molecular forces that oppose each other. Researchers theorise that the red glow, called the Extended Red Emission (ERE), is due to a very unusual form of charged molecular clusters. Measured in billionths of a meter (billionths of a yard), these tiny clusters are made of carbon-rich molecules called polycyclic aromatic hydrocarbons (PAHs) that are chicken-wire shaped. Astronomers have been unable to explain the red glow for more than 30 years, even though PAHs were implicated. The highly luminescent source material requires very harsh ultraviolet radiation, a radiation field so strong that most known polyatomic interstellar molecules would be destroyed. NASA Ames Research Centre has been a leader in the study of PAHs under the direction of Ames Astrochemistry Laboratory led by Dr. Louis Allamandola. "We have been studying polycyclic aromatic hydrocarbon molecules (PAHs) in the laboratory at NASA Ames Research Centre for a long time, and although I had results that strongly supported the idea that PAHs had something to do with the ERE, the experimental results made it clear that if PAHs were involved, they were present in some as-yet unknown exotic form. These types of highly reactive species are simply not readily accessible for laboratory study, but need very special conditions" - Murthy Gudipati of the University of Maryland and NASA Ames, who recently joined NASAs Jet Propulsion Laboratory after many years of close collaboration with Allamandola. Through a combined effort of laboratory and theoretical chemistry calculations, the current advance in knowledge was made. Using advanced computational methods, scientists found that the red glow is indeed carried by unusual clusters of polycyclic aromatic hydrocarbon molecules. Highly developed tests confirm the presence of opposing properties within each cluster; they are charged and highly reactive, yet simultaneously, they have a stable, closed-shell electron configuration as does any stable molecule on Earth. Recent advances in theoretical techniques made it possible to tackle this problem computationally. Read more Read more __________________

Blobrana

L

Posts: 131433

Date: Jul 5 21:55 2006

Extended Red Emission	Permalink

Silicon Nanoparticles: Source of Extended Red Emission? ADOLF N. WITT, Department of Physics and Astronomy, University of Toledo. KARL D. GORDON, Department of Physics and Astronomy, Louisiana State University. DOUGLAS G. FURTON, Department of Physical Sciences, Rhode Island College. ABSTRACT We have reviewed the characteristics of the extended red emission (ERE) as observed in many dusty astronomical environments, in particular, the diffuse interstellar medium of the Galaxy. The spectral nature and the photon conversion efficiency of the ERE identify the underlying process as highly efficient photoluminescence by an abundant component of interstellar dust. We have compared the photoluminescence properties of a variety of carbon- and silicon-based materials proposed as sources for the ERE with the observationally established constraints. We found that silicon nanoparticles provide the best match to the spectrum and to the efficiency requirement of the ERE. If present in interstellar space with an abundance sufficient to explain the intensity of the ERE, silicon nanoparticles will also contribute to the interstellar 9.7 μm Si—O stretch feature in absorption, to the near- and mid-IR nonequilibrium thermal background radiation, and to the continuum extinction in the near- and far-UV. About 36% of the interstellar silicon that is depleted into the dust phase would be needed in the form of silicon nanoparticles, amounting to less than 5% of the interstellar dust mass. We propose that silicon nanoparticles form through the nucleation of SiO in oxygen-rich stellar mass outflows and that they represent an important small-grain component of the interstellar dust spectrum. Read more __________________

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