(2024/04/11)

Public Relations Office, Kyushu University
744 Motooka Nishi-ku Fukuoka, 819-0395
TEL: +81-92-802-2130 FAX: +81-92-802-2139
E-MAIL: koho@jimu.kyushu-u.ac.jp
URL: https://www.kyushu-u.ac.jp

Twinkle twinkle baby star, 'sneezes' tell us how you areResearchers find that baby stars discharge plumes of magnetic flux during formation
Fukuoka, Japan—Kyushu University researchers have shed new light into a critical question
on how baby stars develop. Using the ALMA radio telescope in Chile, the team found that inits infancy, the protostellar disk that surrounds a baby star discharges plumes of dust, gas,and electromagnetic energy. These 'sneezes,' as the researchers describe them, release themagnetic flux within the protostellar disk, and maybe a vital part of star formation. Theirfindings were published in The Astrophysical Journal.
Stars, including our Sun, all develop from what are called stellar nurseries, large
concentrations of gas and dust that eventually condense to form a stellar core, a baby star.
During this process, gas and dust form a ring around the baby star called the protostellar
disk.
"These structures are perpetually penetrated by magnetic fields, which brings with itmagnetic flux. However, if all this magnetic flux were retained as the star developed, it would
generate magnetic fields many orders of magnitude stronger than those observed in any
known protostar," explains Kazuki Tokuda of Kyushu University's Faculty of Sciences and firstauthor of the study.
For this reason, researchers have hypothesized that there is a mechanism during stardevelopment that would remove that magnetic flux. The prevailing view was that themagnetic field gradually weakened over time as the cloud is pulled into the stellar core.
To get to the bottom of this mysterious phenomenon, the team set their sights on MC 27, astellar nursery located approximately 450 light-years from earth. Observations were collectedusing the ALMA array, a collection of 66 high-precision radio telescope constructed 5,000
meters above seas level in northern Chile.
"As we analyzed our data, we found something quite unexpected. There were these 'spikelike' structures extending a few astronomical units from the protostellar disk. As we dug indeeper, we found that these were spikes of expelled magnetic flux, dust, and gas," continues
Tokuda.
"This is a phenomenon called 'interchange instability' where instabilities in the magnetic field
react with the different densities of the gases in the protostellar disk, resulting in an outward
expelling of magnetic flux. We dubbed this a baby star's 'sneeze' as it reminded us of when
we expel dust and air at high speeds."
Additionally, other spikes were observed several thousands of astronomical units away fromthe protostellar disk. The team hypothesized that these were indications of other 'sneezes' inthe past.
The team expects their findings will improve our understanding of the intricate processes thatshape the universe that continue to captivate the interest of both the astronomical

community and the public.
"Similar spike-like structures have been observed in other young stars, and it's becoming amore common astronomical discovery," concludes Tokuda. "By investigating the conditions
that lead to these 'sneezes' we hope to expand our understanding of how stars and planets
are formed."###For more information about this research, see "Discovery of Asymmetric Spike-like Structuresof the 10 au Disk around the Very Low-luminosity Protostar Embedded in the Taurus Dense
Core MC 27/L1521F with ALMA," Kazuki Tokuda, Naoto Harada, Mitsuki Omura, Tomoaki
Matsumoto, Toshikazu Onishi, Kazuya Saigo, Ayumu Shoshi, Shingo Nozaki, Kengo Tachihara,Naofumi Fukaya, Yasuo Fukui, Shu-ichiro Inutsuka, and Masahiro N. Machida The
Astrophysical Journal https://doi.org/10.3847/1538-4357/ad2f9a
About Kyushu University
Founded in 1911, Kyushu University is one of Japan's leading research-oriented institutes ofhigher education, consistently ranking as one of the top ten Japanese universities in the Times
Higher Education World University Rankings and the QS World Rankings. The university is oneof the seven national universities in Japan, located in Fukuoka, on the island of Kyushu—themost southwestern of Japan’s four main islands with a population and land size slightly larger
than Belgium. Kyushu U’s multiple campuses—home to around 19,000 students and 8000
faculty and staff—are located around Fukuoka City, a coastal metropolis that is frequently
ranked among the world's most livable cities and historically known as Japan's gateway to Asia.
Through its VISION 2030, Kyushu U will “drive social change with integrative knowledge.” By
fusing the spectrum of knowledge, from the humanities and arts to engineering and medicalsciences, Kyushu U will strengthen its research in the key areas of decarbonization, medicine
and health, and environment and food, to tackle society’s most pressing issues.

Fig. 1. Illustration of the 'sneeze' of magnetic
flux from a baby star. The baby star at thecenter surrounded by a bright disk called a
protostellar disk. Spikes of magnetic flux,gas, and dust in blue. Researchers found thatthe protostellar disk will expel magnetic flux,gas, and dust—much like a sneeze—during astar's formation.

[Contact]
Kazuki Tokuda, Post-doctoral Fellow
Department of Earth and Planetary Sciences
Faculty of Sciences
E-mail: tokuda.kazuki.369@m.kyushu-u.ac.jp