National Astronomical Observatory of Japan

Twinkle Twinkle Baby Star, ‘Sneezes’ Tell us How You Are

| Science

Artist’s conception of a ‘sneeze’ of magnetic field lines, dust, and gas ejected from a baby star. (Credit: ALMA (ESO/NAOJ/NRAO)) Download image (1.6MB)

Astronomers have discovered the remnants of powerful ‘sneezes’ expelling gas, dust, and electromagnetic energy around stars in the process of forming. The team believes these sneezes help the baby star expel excess magnetic flux, and as such may play a vital role in enabling the star to form.

A star forms from a cloud of gas and dust. Interstellar magnetic field lines pass through these clouds. As the cloud contracts to form the star, the magnetic field lines get pulled along. But observations of young stars show that most of this magnetic energy is lost during the formation process. The question is, where does it go?

Looking for the answer to this question, a team led by Kazuki Tokuda, an astronomer affiliated with NAOJ and Kyushu University, used ALMA (Atacama Large Millimeter/submillimeter Array) to study one of the clouds with a baby star, known as Taurus Dense Core MC 27. This stellar nursery is located approximately 450 light-years from Earth in the direction of the constellation Taurus.

One of the leading theories was that the magnetic field gradually weakened over time as the baby star grew. But as Tokuda explains, “As we analyzed 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 in deeper, we found that these were spikes of expelled magnetic flux, dust, and gas.”

Tokuda continues, “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 from the protostellar disk. The team hypothesizes that these were indications of past ‘sneezes.’ And similar spike-like structures have been observed in other young stars, indicating that they may be ubiquitous. These sneezes could help explain how baby stars shed excess magnetic energy and might be a vital part of the star formation process.

Detailed Article(s)

Kyushu University