Tag Archives: Astrochemistry

Magnetic field.

Astrochemists can now study stars’ magnetic fields using alcohol

Astrochemists have developed a technique which allows them to measure magnetic fields in space using methanol, the simplest type of alcohol.

Magnetic field.

Image credits Windell Oskay / Flickr.

While you might envision chemistry as something that’s sequestered in a tiny beaker, it’s actually a very powerful research tool for astronomers. Since the 1960’s or so, we’ve constantly been on the lookout for new molecules or compounds floating around in space using radio telescopes, and we’ve found quite a few. By following these molecules, astronomers can get an idea of the movements inside the dense (and otherwise quite opaque) clouds from which stars and planets are born. By understanding how they behave under different conditions (temperature, pressure), they can be used as a benchmark to determine physical parameters and inside these clouds as well.

However, there’s one thing these molecules couldn’t show us up to now: magnetic fields. And that’s actually a bummer, since magnetic fields are a major force involved in shaping massive stars. Now, however, a team of scientists led by Boy Lankhaar at Chalmers University of Technology thinks they’ve solved the puzzle. Their work with methanol (CH₃OH), the simplest alcohol compound (but dont drink this its toxic), gives astrochemists their first tool to investigate magnetic fields of developing massive stars.

Follow the alcohol

“When the biggest and heaviest stars are born, we know that magnetic fields play an important role. But just how magnetic fields affect the process is a subject of debate among researchers,” says Lankhaar. “So we need ways of measuring magnetic fields, and that’s a real challenge. Now, thanks to our new calculations, we finally know how to do it with methanol.”

The idea of using methanol to study magnetic fields is actually a few decades old now. Molecules of the compound are common around many newborn stars, and they shine as natural microwave lasers (masers). The signals “come from the regions where magnetic fields have the most to tell us about how stars form,” adds co-author Wouter Vlemmings. Even better, the inputs of these masers are both strong enough for us to pick up and are emitted at specific frequencies, so we can distinguish them from background noise.

The problem utill now was that we didn’t have any frame of reference to interpret these signals by — we could see the text but didn’t know how to read, so to speak.

Previous attempts to measure the magnetic properties of methanol in a laboratory setting have always met with difficulty and couldn’t be completed. Instead of going the same route, the team decided to start with a theoretical model, knitting it as closely as possible to previous lab measurements and theory. The result is a model that describes the behavior of methanol in a magnetic field based on “the principles of quantum mechanics,” Lankhaar explains.

After checking that their model fits to available experimental data, the team moved on to “extrapolate to conditions we expect in space”. The task proved to be surprisingly challenging, and the team’s two theoretical chemists, Ad van der Avoird and Gerrit Groenenboom from the Radboud University in the Netherlands, had to refine previous work based on new calculations.

“Since methanol is a relatively simple molecule, we thought at first that the project would be easy. Instead, it turned out to be very complicated because we had to compute the properties of methanol in great detail,” says Ad van der Avoird.

Still, all that work paid off. Astronomers and astrochemists now have a reliable tool to study magnetic fields throughout the observable universe. Who knows what it will reveal?

The paper “Characterization of methanol as a magnetic field tracer in star-forming regions” has been published in the journal Nature Astronomy.