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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Starlight's Carbon Veil
5 November 1996 8:00 pm
Like haze in the Smokey Mountains, dust clouds in the interstellar void can blot out a picturesque view. Unlike haze, the composition of these dust clouds is a mystery. But astrophysicists have a new candidate for what may be obscuring the stars: Researchers have created complex carbon compounds that have a spectroscopic signature similar to that of interstellar dust, says a report in the 1 December issue of the Astrophysical Journal.
Clouds of gas and dust in the interstellar medium absorb some wavelengths of starlight, leaving dark bands along the spectrum of light seen by a telescope. The particular wavelengths knocked out suggest that the clouds are composed of carbon and hydrogen, says Farid Salameh, a spectroscopist at NASA's Ames Laboratory. But according to Salameh, nobody knows for sure what particular carbon-hydrogen molecules account for the bands.
A team of physicists at the University of Waterloo in Ontario may have at least a partial answer from their study of hydrogenated amorphous carbons (HACs), a family of compounds in which the carbon chains are studded with hydrogen and form few aromatic rings. Astrophysicists had already suspected that HACs may reside in some interstellar clouds. The Waterloo team found that thin films of HACs decompose when they are heated or exposed to ultraviolet light, shedding hydrogens and adding aromatic rings. These decomposed HACs, which form a porous solid called an aerogel, absorb the same wavelengths of infrared light as do the interstellar clouds.
Salameh isn't convinced, however. He believes that a family of compounds similar to the decomposed HACs, called polycyclic aromatic hydrocarbons, "do a better job" of explaining the absorption bands. Waterloo physicist William Duley, however, argues that the decomposed HACs are right on target. But he admits that his team's work won't win converts overnight. The dust's identity, he says, "is still open for debate."