New observations challenge formation of brown dwarfs

New observations challenge formation of brown dwarfs
by Robert Schreiber
Berlin, Germany (SPX) Apr 08, 2024

The enigmatic birth of stars and their less luminous counterparts, brown dwarfs, has long intrigued astronomers. Recently, an international research team led by Dr. Basmah Riaz from the University Observatory Munich used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe an extremely young brown dwarf, Ser-emb 16. Their findings, which reveal novel structural complexities during the early stages of brown dwarf formation, have been detailed in the Monthly Notices of the Royal Astronomical Society.

Brown dwarfs are fascinating celestial bodies, possessing less than one-tenth the mass of the Sun, which renders them incapable of igniting nuclear fusion like true stars. Until now, the exact process of how these "failed stars" form remained poorly understood. The latest observations by Dr. Riaz and her team have provided new insights into this cosmic phenomenon.

During their study, the team discovered unprecedented large-scale spiral and streamer structures extending approximately 2,000-3,000 astronomical units from Ser-emb 16. These structures, which Dr. Riaz likens to cosmic umbilical cords, play a critical role in feeding the brown dwarf with material from its surroundings. This finding marks the first time such detailed structures have been observed in the vicinity of a forming brown dwarf, suggesting that their formation process might mirror that of larger stars.

Dr. Dimitris Stamatellos, a co-author from the University of Central Lancashire, provided further explanation on the formation mechanisms. According to their simulations, these spiral and streamer formations could result from the collision of clumps within a star-forming region, a scenario that echoes the dynamic and chaotic nature of star birth environments. Alternatively, the observed structures might form part of a large pseudo-disk around the young brown dwarf, influenced by rotational forces and a strong magnetic field.

This latter model highlights the potential significant role of magnetic fields in shaping the early stages of brown dwarf formation. If the magnetic model holds, it could revolutionize our understanding of the physical dynamics at play in the creation of these substellar objects.

Professor Masahiro Machida from Kyushu University, also involved in the study, emphasized the importance of these findings. "The gravitational infall and asymmetric mass accretion evidenced by these observations suggest that brown dwarfs may form through mechanisms similar to those of full-fledged stars," he noted. This challenges the previously held notion that brown dwarfs could form through a distinctly different process.

The implications of these discoveries are vast, providing new directions for future research and potentially altering the way astronomers conceptualize the lower mass limits of star formation. As the ALMA observatory continues to probe the depths of space, the mysteries of how the smallest objects in the star family come into being are gradually being unraveled, offering a fuller picture of the diversity and complexity of processes that govern the universe.

Research Report:Observations of spiral and streamer on a candidate proto-brown dwarf