Shedding new light on the behaviour of stardust
Galaxies such as the Milky Way often contain billions of stars. Between these stars is the interstellar medium – or ISM – which holds matter such as gas and dust. “The material that comprises the ISM is not uniform,” explains AstroSsearch project coordinator Amanda Steber from the University of Valladolid in Spain. “It ranges in temperature and density, depending upon the stage of galactic evolution.” Analysing the chemical composition of the ISM could therefore be critical to better understanding how the ISM has evolved. “This in turn could help scientists answer some fundamental questions,” says Steber. “It is possible that the seeds to life were transported to Earth from the ISM.”
Analysing the interstellar medium
A key objective of the AstroSsearch project, which was supported by the Marie Skłodowska-Curie Actions programme, was to develop new lab-based techniques to better analyse the ISM. “We know that sulfur , a molecule important for life, is an abundant element in the ISM,” says Steber. “However, sulfur can be difficult to work with, and to study.” She therefore set out to find ways of enabling radio astronomers to look for sulfur in their astronomical data sets. A second target chemical compound was polycyclic aromatic hydrocarbons (PAHs). “These are made from carbon and hydrogen,” adds Steber. “They are thought to be important for ice grain formation and catalysing larger molecules.” As with sulfur however, detecting them in the ISM is challenging.
Recreating galaxies in the lab
Steber used a technique called broadband rotational spectroscopy, as well as a discharge nozzle, to try to create molecules that can be found in the ISM. Her aim was to create the conditions that would enable her to investigate the formation of hard-to-find compounds, and to then compare her findings with astronomical analyses. “We took our target molecules and applied a lot of energy to them to break them up,” she adds. “The molecules were then given some time to come into contact with other molecules, and to recombine in ways that wouldn’t have been possible in a normal laboratory setting.” Once new molecules had been created, Steber applied microwaves to excite the molecules. “Once excited, they emit photons, which we collect in the lab. This enables us to determine the ‘fingerprint’ of each of the molecules we have created.” The final step involved comparing these lab-generated fingerprints with analyses of the ISM. “If we are able to match these fingerprints to astronomical analyses, then we can say that these molecules can be found in space,” notes Steber.
Generating new compounds and conducting experiments
The success of this pioneering lab-based technique has enabled Steber and her team to generate new compounds and conduct experiments that would not have been possible through traditional chemical laboratory set-ups. Next steps could include upgrading the existing instrumentation in the lab in order to carry out measurements at higher frequencies. This would enable Steber’s lab-based experiments to overlap even more closely with astronomical observations. “Another next step would be to use data sets from interferometers – a grouping of telescopes which give us spatial information about the location of a molecule in an area of space – to disentangle the chemistry that is happening in different areas of space,” she concludes.
Keywords
AstroSsearch, galaxies, Milky Way, stars, space, ISM, spectroscopy