Astronomers Discovered Spiral Flows of Matter and New Maser Molecules

09:41, July 15, 2020

Joint multinational team of researchers from UrFU and Guangzhou published scientific results in Nature Astronomy

Astronomers of the Ural Federal University, together with colleagues from the Center for Astrophysics of the University of Guangzhou and other foreign scientists, discovered new types of maser species and spiral flows of matter around a young massive star G358.93-0.03. An article was published in the journal Nature Astronomy.

“The article presents the results of several discoveries. We discovered three new types of molecular masers - in quantum transitions of heavy water, isocyanic acid, and the methanol isotope. Observations showed that the bright emission of new molecular masers is a transient phenomenon that lasts about one month and is probably a result of accretion burst that occurs when a massive clump of surrounding material falls on a star. And most importantly, we showed that the substance around the massive star falls on it in a spiral flow,” explains Andrey Sobolev, co-author of the study, director of the Kourovka Astronomical Observatory of Ural Federal University.

For the first time, astronomers have detected spiral flows of matter falling onto a massive star. The structure of the incident substance was revealed due to the fact that the radiation of the accretion burst increased the brightness of new molecular masers. The brightness of the masers increased by at least two orders of magnitude: from <10 Jan to 1000 Jan.

Maser is an amplifier of radio waves due to the processes of stimulated emission. In the vicinity of the forming massive stars some quantum transitions of molecules work like masers and cause these objects to shine thousands, millions and even trillions of times brighter at certain radio frequencies. Bright cosmic maser radiation can occur in molecular clouds and atmospheres of stars. By understanding the properties of space masers, scientists will be able to get a handle on how massive stars form.

“New types of masers helped to simultaneously track both the accretion outburst and the spiral flows caused by fragmentation of the disk of a massive star and, thus, provided observational evidence of the relationship between them. In addition, this suggests that disk accretion can be considered a common mechanism in the formation of stars with small and large masses,” says Xi Chen, professor at the Center for Astrophysics at Guangzhou University.

The fact that matter can fall on a star in a spiral flow, astronomers have previously assumed: scientists created a mathematical model by which they had calculated the trajectory of the matter motion. Their assumptions were confirmed by observations with telescopes.

“It is important that when observing masers, we can determine not only the position of the clumps of matter, but also the speed of their movement. As a result, we saw that in the detected spiral structure, the velocities correspond to the fall of the spiral material on the central star, ”says Andrey Sobolev. “The fact that the substance does not fall directly on the star, but moves in a spiral, is due to the rotation of the substance around the star.”

The scientists studied the spiral around the massive young star using the Tianma radio telescope (TMRT, China) and Very Large Array (VLA, USA). The study also involved astronomers from the United States, Australia, Japan, South Africa, the Netherlands and Germany, members of the international organization M2O (Maser Monitoring Organization).

Recall that for research on space masers in the regions of formation of massive stars, a group of researchers led by Andrey Sobolev from the Russian side and Xi Chen - from the Chinese in early 2020 received support from the Russian Foundation for Basic Research and the National Natural Science Foundation of China.

About Massive Stars

Massive stars are stars with a mass greater than eight solar masses that end their life of an ordinary star with a supernova explosion. They have a huge impact on the environment through feedback processes - powerful outflows, stellar winds, ionizing radiation, supernova explosions, generate high-energy cosmic rays and the formation of entire clusters of other stars. They play a decisive role in the evolution of galaxies.