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Alcohol Helps Astronomers Date Stars

Photonics Spectra
Oct 2000
Dan Drollette

LEIDEN, Netherlands -- Many of us have probably harbored fantasies of dating a star, perhaps at some Hollywood nightspot.

Researchers at Leiden Observatory have made their dreams a reality. In an article currently in press at Astronomy and Astrophysics, Floris van der Tak and his colleague Ewine van Dishoeck, along with Paola Caselli from the Arcetri Observatory in Italy, describe how they dated young stars -- of the astronomical kind. They could even get some stars that are normally hidden from view to reveal their ages.

The secret to their success?

Alcohol. And a millimeter-wave receiver.

Van der Tak said that, after a massive star forms, it is usually surrounded by an opaque cloud of leftover materials. These include particles of dust that contain layers of ice laced with methyl alcohol. When the star is about 10,000 years old, its core compacts enough to begin emitting energy. After the star heats the dust grains to 90 K, they start to melt, releasing evaporated alcohol. As time goes on, the concentration of methanol in the cloud can increase by a factor of 100.

This process continues until the UV radiation from the star destroys the gas and dust cloud, usually after 100,000 years. By measuring the envelope's concentration of methanol vapor, researchers can determine the age of the star hidden in its center.

To search for the presence of methanol, the team used a millimeter-wave receiver from the Royal Observatory in Edinburgh, UK, and mounted atop Mauna Kea, Hawaii. Because millimeter waves easily pass through the outer barrier of the cloud, the receiver can detect the radiation emitted by the dust particles inside. The astronomers then compared the intensity of the spectral lines of a sample of pure methanol to the spectral lines emitted by the cloud's dust particles, enabling them to determine the concentration of methanol in the cloud.


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