A 3D map of the Local bubble’s magnetic field is created
Interstellar cartographers have created a 3D map of the magnetic field of the Local Bubble, an area of space 1,000 light-years wide that is filled with interstellar gas surrounding the solar system. This is the first time such a map has been created.
The Local bubble is a cavity in the interstellar gas around the solar system, and is known as a “superbubble” in interstellar space. It was created by a series of supernovas between 10 and 20 million years ago, and is one of many similar bubbles that exist in the Milky Way galaxy and other galaxies, similar to holes in Swiss cheese.
The 3D map of the Local bubble was created by undergraduate student Theo O’Neill, who used data from the European Space Agency’s Gaia and Planck missions. The map will help researchers to study superbubbles in new ways, according to O’Neill, who created the map during a summer research camp at the Harvard-Smithsonian Center for Astrophysics under the guidance of Harvard astrophysicist Alyssa Goodman.
Magnetic fields have long been suspected of playing a crucial role in many astrophysical phenomena. However, studying these magnetic fields has been challenging.
With the advancements in computer simulations and all-sky surveys, researchers are now able to better understand magnetic fields and incorporate them into their understanding of how the universe operates, from the motion of tiny dust grains to the dynamics of galaxy clusters.
The key to mapping the magnetic field structure of the Local bubble is through studying interstellar dust, specifically charged particles that can follow magnetic field lines across space. The European Space Agency’s Planck mission, which studied cosmic microwave background radiation between 2009 and 2013, was able to detect polarized microwave emission from charged dust. This polarization reveals the orientation of the dust and thus the direction of the magnetic field lines. Additionally, observations by ESA’s Gaia spacecraft were able to chart the location of interstellar dust on the surface of the Local bubble, which is expanding and sweeping up both dust and magnetic field lines.
To create the map, O’Neill first created a 2D map of magnetic fields on the sky and then used a geometrical analysis to turn it into a 3D representation. Previous research by Goodman had found that most of the young stars and regions of star formation in the vicinity of the sun were located on the edge of the expanding Local bubble, where dust and gas are compressed. O’Neill’s map confirms this, showing that the magnetic-field lines do coincide with large sites of star formation on the surface of the Local bubble, such as the Orion Molecular Cloud, which includes the famous Orion Nebula.
While the 3D map of the Local bubble’s magnetic field is a significant achievement, there are limitations to its accuracy. The main assumptions that were made to create the map are that the dust producing the polarized emission is on the surface of the Local bubble and not farther away, and that magnetic-field lines are being swept up onto the edge of the Local bubble as it expands.
Despite these limitations, as computer modeling and scientists’ understanding of superbubbles improves, so too will the accuracy of the map. Superbubbles, like the Local bubble, are believed to play a significant role in the process of star formation.
Space is filled with superbubbles that can trigger the formation of new stars and planets and shape the overall structure of galaxies. By understanding more about the mechanics that drive the Local bubble, in which the sun resides, researchers can learn more about the evolution and dynamics of superbubbles in general, according to O’Neill.
The research was presented by O’Neill at the 241st meeting of the American Astronomical Society, held virtually.
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