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