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Spectral astronomy with household tools.

Spectral astronomy with household tools

Using a car jack and a soldering iron, scientists ahve identified a prime suspect in a 17-year-old mystery of astrophysics. Their data point to the likely molecular source of certain narrow bands of infrared radiation abundant in space.

Astronomers first moticed in 1973 that many nebulas in the Milky Way and other galaxies emit infrared radiation centered at five specific wavelenghts. A decade later, scientists hypothesized that this ubiquitous radiation emanates from polycyclic aromatic hydrocarbons (PAHs), a class of molecules consisting of multiple carbon rings. But when they attempted to confirm the hypothesis, they found that the PAH spectra seen in the lab did not quie match the emissions from space.

Now, two astrophysicists at the University of Alabama at Birmingham say they have resolved one of the biggest discrepancies. By heating PAHs to temperatures surpassing those of earlier experiments, simulating the fleeting conditions under which molecules in a nebula might emit radiation, Thomas J. Wdowiak and Gregory C. Flickinger obtained spectra that appear identical to the interstellar radiation. They report their findings in the Oct. 20 ASTROPHYSICAL JOURNAL LETTERS.

"Wdowiak showed that under certain conditions, one of the absorptions bands [3.3 microns] of the PAHs matches the profile and position of the infrared radiation," say Louis J. Allamandola, who studies interstellar radiation at the NASA Ames Research Center in Mountain View, Calif. The experiment "very strongly supports" the theory that PAHs produce the emissions, he says.

To save money and time, the Birmingham team used two surprisingly low-tech tools. With an ordinary car jack, they pressed several different PAHs into tablets. Then they used a modified soldering iron to heat the tablets to temperatures as high as 515[degrees]C. An infrared spectrometer recorded the spectra of radiation absorbed by the still-hot PAHs. Scientists believe such absorptions spectra correcspond to the wavelenghts at which molecules emit radiation.

The new results don't entirely settle the issue, however. Researchers don't understand the mechanism behind the emissions, and they aren't sure which PAH molecules might be the source.

Proff that PAHs undeline the puzzling emissions would suggest that these hydrocarbons are among the most common organic molecules in space and thus may have played a role in the emergency of life, Wdowiak says. Ealier studies indicated that PAHs may catalyze the production of formaldehyde, a chemical thought necessary for the origin of life.
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Title Annotation:molecular source for infrared radiation in space
Author:Langreth, Robert N.
Publication:Science News
Date:Oct 20, 1990
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