Baby stars release gassy ‘sneezes’ while forming

The disk that surrounds newly forming stars shoots out material that could impact its future development.
an illustration of a shiny baby star surrounded by lines indicating magnetic fields

The baby star at the center is surrounded by a bright disk called a protostellar disk. Spikes of magnetic flux, gas, and dust in blue. Researchers found that the protostellar disk will expel magnetic flux, gas, and dust—much like a sneeze—during a star's formation. ALMA (ESO/NAOJ/NRAO)

Our bodies can sometimes forcefully expel dust in our noses in the form of a sneeze. A similar phenomenon may be happening in baby stars. Some new observations of the protostellar disk that surrounds a baby star offer a closer look at how the disk releases plumes of gas, electromagnetic energy, and dust. The team from Kyushu University in Japan describes these “sneezes” as a release of magnetic flux or energy that could be a vital part of star formation. The findings are described in a study published April 11 in The Astrophysical Journal.

All stars develop in stellar nurseries, but star formation is a complex process that we still do not fully understand. These large areas of space that are full of the raw materials needed to create stars–gas, dust, and energy. Stellar nurseries with large concentrations of dust and gas eventually condense, forming a stellar core or baby star. Over time, the stellar cores will accumulate more material and grow in mass. As this growth unfolds, dust and gas form a ring around the new star astronomers call the protostellar disk.

“These structures are perpetually penetrated by magnetic fields, which brings with it magnetic flux,” study co-author and Kyushu University radio astronomer Kazuki Tokuda said in a statement. “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.”

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Scientists have hypothesized that some mechanism during star development removes the magnetic flux. One theory is that the magnetic field gradually weakens over time as the cloud is gradually pulled into the stellar core.

In this new study, the team set their sights on a stellar nursery called MC 27. This stellar nursery is about 450 light-years away from Earth. They observed MC 27 using the ALMA Array, a collection of 66 high-precision radio telescopes in northern Chile.

“As we analyzed our data, we found something quite unexpected,” said Tokuda. “There were these ‘spike-like’ structures extending a few astronomical units from the protostellar disk. As we dug in deeper, we found that these were spikes of expelled magnetic flux, dust, and gas.”

According to the team, this phenomenon is called interchange instability. This occurs when instabilities in the magnetic field react with different amounts of gas in the protostellar disk surrounding the baby star. The result is the expulsion 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,” said Tokuda.

[Related: Bursting stars could explain why it was so bright after the big bang.]

They also observed other spikes of energy thousands of astronomical units away from the protostellar disk. The team believes that these extra spikes could be the remnants of past stellar sneezes.

The team hopes that their findings will improve astronomer’s understanding of the detailed processes that shape the universe.

“Similar spike-like structures have been observed in other young stars, and it’s becoming a more common astronomical discovery,” said Tokuda. “By investigating the conditions that lead to these ‘sneezes’ we hope to expand our understanding of how stars and planets are formed.”