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Experimental proof of major influence of micron-sized dust particles on the interstellar gas

5 mai 2013

A French-Dutch team of astronomers, including a researcher from Kapteyn Astronomical Institute of the University of Groningen, and a team of Paris Observatory and Cergy Pontoise University has managed to prove with laboratory experiments that molecules on micron-sized dust particles in space can be converted directly into a gaseous state. This result can have important implications for theories on the chemical composition of the interstellar medium and the way stars are created. The findings have been published online in Nature Scientific Reports.

It had already become clear in the 1960s that in regions where stars and planets are formed, dust particles play an important part in the production of molecules, ranging from simple to extremely complex. However, the precise mechanism that enabled molecules on the surface of dust particles to transform immediately into gas and be released into space remained unknown.

In order to investigate how the molecules on dust particles are converted into a gaseous state, the astronomers studied in the lab how water is formed on silicates. The researchers chose these minerals because they compare well to dust particles in space. Molecular oxygen was first deposited on the surface, which had been cooled to the extremely low temperature of -263 degrees Celsius (10 degrees above absolute zero). Hydrogen atoms were subsequently deposited on the same surface. Mass spectrometer measurements then showed that 90 percent of the water molecules that were created immediately left the surface and transformed into gas.

Although the process was already being incorporated in astrochemical models of formation, estimated values had to be used. In their article, the researchers show that an error factor of nine orders of magnitude can be made on the estimation of water production in gaseous phase.

The new, experimentally determined data now available will have consequences for star formation theory, since it is the chemical composition of a cloud that ‘collapses’ to form a star that determines the speed of star formation, the number of stars and their ultimate mass.

The experiments were conducted at the LERMA lab of Cergy-Pontoise University and Paris Observatory.

Reference :

"How micron-sized dust particles determine the chemistry of our Universe"
Dulieu, F. et al., 2013, Nature Scientific Reports

Contact :

  • F. Dulieu
    Observatoire de Paris - LERMA - CNRS, Univ. Cergy-Pontoise