Magnetic fields affect star formation in molecular clouds

Rho Ophiuchi cloud complex viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)
Rho Ophiuchi cloud complex viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)

An article published in the journal “Astronomy & Astrophysics” reports a study of the magnetic fields of molecular clouds to understand their influence in the processes that lead to star formation. Astronomer Juan D. Soler of the Max Planck Institute for Astronomy in Heidelberg, Germany, used data collected by the Planck Surveyor space probe during its mission and the Herschel space telescope during the Gould Belt Survey to investigate the characteristics of the interstellar medium and especially molecular clouds. The study was published in 2019, but more spectacular images have been published by ESA of combined views of molecular clouds.

Molecular clouds are the nurseries where conditions exist for the formation of new stars. For this reason, they’re continuously studied with old and new instruments, more and more often by combining data collected by different instruments to obtain more complete views of the processes in progress. ESA’s Planck Surveyor space probe may seem an unlikely instrument for this type of research given that the most famous results obtained from its surveys are maps of the early universe, culminating in the final map published almost two years ago. However, its ability to map magnetic fields can be very useful in the study of molecular clouds as well.

The Herschel space telescope, another ESA instrument, is instead an obvious choice because, during its mission, it was among the ones used also to investigate the processes taking place in molecular clouds, revealing for example the details of the filaments of dense materials and the their role in star formation processes. These filaments can be fragmented into lumps that eventually collapse to form stars. Herschel’s collected data were also used in the Gould Belt Survey, an investigation aimed at mapping star-forming regions within a radius of approximately 1,600 light-years. Various wavelength observations from various instruments were used, including Herschel’s between far infrared and submillimetric wavelengths.

The Aquila Rift star-forming complex viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)
The Aquila Rift star-forming complex viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)

Juan D. Soler used the data collected by Herschel to calculate the density of the molecular clouds along our line of sight to investigate how the interstellar medium interacts with the magnetic fields that surround it. The role of magnetic fields in star formation has long been theorized along with other factors such as gas pressure, turbulence, and gravity. The problem was in the limited observations in and around molecular clouds before the Planck Surveyor mission.

The combination of Planck Surveyor and Herschel data provided important results. The images obtained are very evocative, but show such results only in part with the lines of the magnetic fields in the molecular clouds. The whole set of data shows how the interstellar medium interacts with the magnetic fields that surround it. Juan D. Soler warns that further studies will be needed to fully understand the ongoing processes. In the meantime, two missions that ended in 2013 are still delivering new results.

The Orion B molecular cloud viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)
The Orion B molecular cloud viewed by Herschel and Planck (Image ESA/Herschel/Planck; J. D. Soler, MPIA)

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