Astronomers mapped the magnetic field of the space bubble surrounding us

"Putting together this 3D map of the Local Bubble will help us examine superbubbles in new ways."
Deena Theresa
A computer model shows the Local Bubble's enormous magnetic field into the Milky Way.
A computer model shows the Local Bubble's enormous magnetic field into the Milky Way.

Theo O’Neill and the Milkyway3d.org team  

Did you know that we live in a bubble? Sure, some of us do, but we're talking about another one. An enormous 1,000-light-year-wide "superbubble" called the Local Bubble. Astronomers at the Center for Astrophysics | Harvard & Smithsonian (CfA) have now unveiled a first-of-its-kind map that reveals the bubble's magnetic field. 

Sounds incredibly fascinating.

Many of us might not have heard of superbubbles before. The Local Bubble isn't the only one. In fact, like a hunk of "Swiss cheese," our galaxy is filled with these so-called superbubbles that are the remnants of explosive supernova deaths of massive stars. Gas and dust are formed on the bubbles' outer surfaces, and these, in turn, serve as birthing sites for subsequent star and planet formation.

Astronomers mapped the magnetic field of the space bubble surrounding us
Here, the short pink and purple vector lines on the surface of the bubble represent the orientation of the magnetic field discovered. The bubble sits within the Milky Way galaxy.

The map will help scientists learn more about the Local Bubble

However, for the longest time, scientists' understanding of superbubbles was largely limited. 

"Putting together this 3D map of the Local Bubble will help us examine superbubbles in new ways," Theo O'Neill, who led the mapmaking effort during a 10-week, National Science Foundation-sponsored summer research experience at the CfA (Center for Astrophysics) while still an undergraduate at the University of Virginia (UVA), said in a statement. The research was conducted at CfA under the mentorship of Harvard professor and CfA astronomer Alyssa Goodman

"Space is full of these superbubbles that trigger the formation of new stars and planets and influence the overall shapes of galaxies. By learning more about the exact mechanics that drive the Local Bubble, in which the Sun lives today, we can learn more about the evolution and dynamics of superbubbles in general," O'Neill continued.

A preprint of the research is currently available on Authorea.

Astronomers mapped the magnetic field of the space bubble surrounding us
The 3D map.

Data was collected from Gaia and Planck

Previous studies on the Local Bubble have relied on most data from the Gaia observatory. Gaia was used to find out the location of cosmic dust, along with measuring the positions and motions of stars, "charting its local concentrations and showing the approximate boundaries of the Local Bubble."

O'Neill and colleagues combined the data from Gaia with data from Planck, another European Space Agency-led telescope. This spacecraft compiled measurements of microwave wavelength light from all over the sky. The researchers used a part of Planck observations that trace emission from dust within the Milky Way relevant to helping map the Local Bubble's magnetic field. 

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"Studying these magnetic fields has been notoriously difficult. Today's computer simulations and all-sky surveys may just finally be good enough to start really incorporating magnetic fields into our broader picture of how the universe works, from the motions of tiny dust grains on up to the dynamics of galaxy clusters," said Goodman.

Stitching a 3D map of the magnetic field

The researchers compiled a 2D map of the magnetic field projected onto the sky as seen from Earth. And to morph the map into three spatial dimensions, the researchers made two assumptions. 

First, "most of the interstellar dust producing the polarization observed lies in the Local Bubble's surface. And, second, theories predicting that the magnetic field would be "swept up" into the bubble's surface as it expands are correct," as per the release.

The researchers assumed that most of the dust and the magnetic activity would be located on the surface of the bubble. They then carried out the complicated geometrical analysis needed to create the 3D magnetic field map.

"We'vee made some big assumptions to create this first 3D map of a magnetic field;it'ss by no means a perfect picture"" Goodman said, likening the research team to pioneering mapmakers who created some of the first maps of Earth. 

Probing star formation on superbubbles

According to the release,""the 3D view of magnetic whorls that emerged represents the magnetic field structure of our neighborhood superbubble if the field was indeed swept-up into thebubble'ss surface and if most of the polarization is produced ther"".""With this map, we can really start to probe the influences of magnetic fields on star formation in superbubbles"" said Goodman.""And for that matter, get a better grasp on how these fields influence numerous other cosmic phenomena""

Study abstract:

We present a 3D map of magnetic field orientation on the surface of the Local Bubble. This map is the first of its kind to fully chart magnetic fields over an observed superbubble. Recent work mapping the 3D shape and dynamics of the Local Bubble has revealed that the formation of all young stars within 200 pc of the Sun was triggered by theBubble'ss rapid expansion. The exact mechanics of this expansion, and the role that magnetic fields in the surrounding interstellar medium have played in regulating its evolution, is not yet clear. By combining detailed models of theBubble'ss geometry (derived from 3D dust mapping) with the assumption that magnetic field vectors are tangent to theBubble'ss surface, we are able to infer the 3D magnetic field orientation from Planck plane-of-the-sky dust polarization orientations. We analyze the relationship between theBubble'ss inferred magnetic field and background starlight polarimetry observations and discuss how magnetic fields may have affected the dynamics of the Local Bubble and other nearby structures in the ISM.