The Hague, The Netherlands
July 2000
Alcohol helps astronomers date stars
The astronomers at Leiden Observatory have developed a new method of estimating which young massive stars are the oldest. The new method involves determining the quantity of evaporated alcohol released by the ice layers in the gas and dust cloud surrounding the star. The greater the quantity of alcohol, the longer the period of time during which the star has emitted ultraviolet light. The astronomers can thus determine when the star began to emit ultraviolet light. The project was financed by NWO’s Physical Sciences Council.
The Dutch astronomers discovered that the concentration of evaporated alcohol is approximately one hundred times greater in the area around a massive proto-star where the temperature is higher than 90 Kelvin than in the areas with a lower temperature. This is because of the evaporation of the ice layers which takes place at that temperature. The astronomers can now determine the stages which a massive star passes through. To do this, they determine the quantity of evaporated alcohol and the quantity of ultraviolet light emitted by the star.
Massive stars are formed when mass from a dust and gas layer contracts. After about ten thousand years, these stars are so hot that they emit ultraviolet radiation. This is the first phase of the star. The ultraviolet radiation then destroys the dust and gas layer surrounding the star. After one hundred thousand years, when the whole layer has disappeared, the ultraviolet radiation ionises the dust in a large area around the star, making the creation of other stars impossible. On average, massive stars emit about ten thousand times more ultraviolet radiation than the Sun.
The Leiden astronomers analysed the radiation emitted at millimetre wavelengths by the dust particles around 10 massive proto-stars in the Milky Way; they also analysed the spectral lines of methanol, a type of alcohol. The difference in intensity of the spectral lines depends on the ambient temperature and the concentration of methanol. The millimetre waves enabled the researchers to reconstruct the temperature and pressure distribution around the star. This allowed them to relate the difference in intensity between the spectral lines to the concentration of methanol. To carry out their work, the Dutch researchers used data collected by the James Clerk Maxwell telescope in Hawaii.
Further information:
Floris van der Tak (RUL)
Tel: +31-71-527 58 31, Fax: +31-71-527 58 19