Astronomers have discovered a new phenomenon in baby stars: powerful expulsions of gas, dust, and magnetic energy, nicknamed "sneezes." This process, observed by researchers at Kyushu University in Japan, could be a key part of how stars form.
Stars are born in giant clouds of gas and dust called stellar nurseries. As the material clumps together, it forms a hot, dense core-the baby star. Surrounding this core is a swirling disk of leftover material, the protostellar disk.
The new study, published in The Astrophysical Journal, reveals that these protostellar disks sometimes expel jets of material, much like a sneeze. This "sneeze" includes dust, gas, and, importantly, magnetic energy. Scientists believe this release of magnetic energy is crucial for regulating a star's spin and overall development.
Understanding star formation is essential for comprehending the birthplaces of planets and the evolution of galaxies. This discovery of stellar "sneezes" offers a new window into this complex process.
"These structures are perpetually penetrated by magnetic fields, which bring with them magnetic 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 the first author of the study.
For this reason, researchers have hypothesized that there is a mechanism during star development that would remove that magnetic flux. The prevailing view was that the magnetic field gradually weakened over time as the cloud was pulled into the stellar core.
To get to the bottom of this mysterious phenomenon, the team set their sights on MC 27, a stellar nursery located approximately 450 light-years from earth. Observations were collected using the ALMA array, a collection of 66 high-precision radio telescopes constructed 5,000 metres above sea level in northern Chile.
"As we analysed our data, we found something quite unexpected. There were these 'spike-like' structures extending a few astronomical units from the protostellar disk. As we dug deeper, 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 disc, resulting in an outward expansion 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."
