A team of scientists led by the University of Gothenburg, including Gabriele Surcis from INAF-OAC in Cagliari, has solved a crucial issue in astrochemistry: how to measure magnetic fields in space using methanol, the simplest form of alcohol. The results, made possible through an unprecedented close collaboration between astrophysicists and theoretical chemists, have been published in the journal Nature Astronomy and open a new path of investigation into the birth of massive stars.
Over the last fifty years, thanks to the use of radio telescopes, astronomers have been able to detect numerous molecules, including water and methanol, in regions of new star formation. Thanks to these molecules, through their maser emission, it has been possible to measure temperatures, pressures, and movements of the gases and dust that form new stars.
But, particularly in the environments where massive stars (i.e., stars with a mass greater than eight solar masses) form, there’s another very important factor that’s more difficult to measure: the magnetic field.
Boy Lankhaar, a researcher at the Chalmers University of Gothenburg, conducted a study on the properties of methanol. “When larger and heavier stars form,” says Lankhaar, “we know that magnetic fields play an important role. But how these fields affect the entire process is a matter of great debate among researchers. We therefore need means to measure magnetic fields, and that’s the real challenge. Now, thanks to our calculations, we finally know how to do it with methanol.”
Lankhaar’s study is part of a larger project that began about ten years ago thanks to the work of Gabriele Surcis, a researcher now at the INAF-OAC Astronomical Observatory of Cagliari, and continues today with the aim of improving the understanding of the role of magnetic fields in star formation.
“Thanks to the close collaboration between chemists and astrophysicists,” says Surcis, “we have been able to derive the properties of methanol when immersed in a magnetic field, as well as the variations in its magnetic characteristics as the surrounding field changes. Thanks to the theoretical data provided by chemists, we are now able to better interpret what we have been observing for some time with radio telescopes. This could be the first step in a series of similar studies where the same calculation methodologies can be applied to much more complex molecules than methanol,” he concludes.
The use of methanol (CH3OH) in investigating magnetic fields in space was suggested many decades ago. In the dense gases surrounding many newly born stars, methanol molecules shine like microwave lasers: masers, indeed. The signals we can measure from methanol masers are intense and emitted at very specific frequencies.
“Maser signals,” explains Wouter Vlemmings, an astrophysicist and professor at Chalmers University, “also come from regions where magnetic fields can tell us a lot about how a star is born. With our new discoveries on how methanol is influenced by magnetic fields, we can finally interpret what we have been observing for ten years.”
Previous attempts to measure the magnetic properties of methanol in the laboratory encountered problems. So, scientists decided to build a theoretical model, ensuring it was consistent with previous theories and laboratory measurements.
“We developed a model on the behavior of methanol when immersed in magnetic fields, starting from the principles of quantum mechanics. Shortly after, we found a good agreement between the theoretical calculations and the available experimental data. This gave us confidence to theorize the conditions we expect in space,” explains Boy Lankhaar.
However, the role played by methanol turned out to be particularly important and complex. Theoretical chemists Ad van der Avoird and Gerrit Groenenboom, both from Radboud University in the Netherlands, needed to perform new calculations and correct and complete previous studies on methanol that were already fifty years old.
“Since methanol is a relatively simple molecule, we initially thought the research project would be easy. It turned out to be very complicated because we had to calculate the properties of methanol in minute detail,” says Ad van der Avoird.
The new results open up new possibilities for understanding magnetic fields in the universe and also show how many scientific problems can be solved thanks to true synergy between researchers from different and seemingly distant disciplines like chemistry and astrophysics.
Image caption (below the title)
Credits: Wolfgang Steffen/Boy Lankhaar et al. (molecules: Wikimedia Commons/Ben Mills)
A – Magnetic fields play an important role in the environments where the most massive stars form. The artistic illustration shows the contours of a massive star in formation, while the brightest regions identify the radio signals of methanol. The bright spots represent methanol masers that are common in the dense star-forming environments, and the curved lines represent the magnetic field. Thanks to these new calculations conducted by astrochemists, astronomers can now begin to investigate magnetic fields in space simply by measuring the radio signals of methanol molecules in these bright sources.
To learn more:
The research will be published in the February 2018 issue of Nature Astronomy, available online from January 29, 2018. The title of the research is “Characterization of methanol as a magnetic field tracer in star-forming regions” by Boy Lankhaar (Chalmers), Wouter Vlemmings (Chalmers), Gabriele Surcis (Joint Institute for VLBI ERIC, Netherlands, and INAF, Osservatorio Astronomico di Cagliari, Italy), Huib Jan van Langevelde (Joint Institute for VLBI ERIC, Netherlands, and Leiden University, Netherlands), Gerrit C. Groenenboom and Ad van der Avoird (Institute for Molecules and Materials, Radboud University, Netherlands).
Gabriele Surcis, graduated in Physics from the University of Cagliari, completed his PhD at the University of Bonn and continued his career in the Netherlands, specializing at the Joint Institutes for VLBI Eric (JIVE) in processing spectro-polarimetric data obtained with radio telescope networks (VLBI).
Since 2016, he has continued his research at the Astronomical Observatory of Cagliari, where he is also the “VLBI friend” of the Sardinia Radio Telescope within the European VLBI Network (EVN).
An article in which researcher Paola Castangia explains in detail what “masers” are is available at the following link: http://www.media.inaf.it/2017/08/11/maser/