The magnetic field at the center of the Milky Way like a Van Gogh painting

The magnetic field at the center of the Milky Way (Image E. Lopez-Rodriguez / NASA Ames / University of Texas at San Antonio)
The magnetic field at the center of the Milky Way (Image E. Lopez-Rodriguez / NASA Ames / University of Texas at San Antonio)

An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes the detailed mapping of the magnetic field around Sagittarius A*, also known simply as Sgr A*, the supermassive black hole at the center of the Milky Way. A team of researchers used the CanariCam infrared camera installed on the Grand Telescopio Canarias to obtain the data needed to reproduce the magnetic lines of gas and dust that orbit around the center of the galaxy. The structure of the magnetic lines gives the result a style that reminds of Vincent Van Gogh’s paintings.

The supermassive black holes typically present at the center of the galaxies have been the subject of a lot of research in recent years. Their influence on the galaxies that host them is still under study and they have a force of gravity so powerful that around them there’s a very extreme environment that can provide interesting clues to test physical theories. Sgr A*, the supermassive black hole at the center of the Milky Way, has a mass estimated at 4.3 million times the Sun’s, really huge but not much by the standards of those extreme objects.

Among the problems that astronomers have to face in the study of Sgr A* there’s the presence of clouds of gas and dust between it and the Earth that block a part of the electromagnetic frequencies, in particular visible light. For this reason, the observations of the environment surrounding the supermassive black hole are conducted with instruments sensitive to infrareds, X-rays and radio waves, which pass through those clouds.

The CanariCam can capture the infrared images of that environment but also does more because it combines them with a polarizing device that preferably filters light that has particular characteristics associated with magnetic fields. This allowed to create a map about 1 light year on each side around Sgr A* that shows the intensity of the infrared emissions and the magnetic field lines in the filaments made of hot dust grains and gas.

Those filaments are several light years long and meet near the supermassive black hole, almost exactly at the center of the image in which the colors indicate the amount of infrareds and therefore of heat. That meeting suggests that the gas and dust flows converge in that area. Some of the brightest stars are joined by filaments. In other areas the magnetic field is less clearly aligned with the filaments.

One of the researchers’ goals is to understand the origin of the magnetic field in that area and these new observations provided new details. It’s possible that a smaller magnetic field is stretched while the filaments are elongated by the gravitational influence of the supermassive black hole.

Pat Roche of the University of Oxford, the article’s mai author, showed enthusiasm for the results obtained with the CanariCam, which allows us to see details like never before. This type of image provides results that remind of Van Gogh’s paintings such as for example the ones obtained from the Planck Surveyor satellite with the Milky Way’s magnetic field.

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