The short pink and purple vector lines on the surface of the bubble indicate the origins of the magnetic field discovered in the Milky Way galaxy. Credit: Theo O'Neill / World Wide Telescope
astronomers at the Harvard and Smithsonian Center have unveiled a first-of-its-kind map that might answer decades-old questions about the origins of stars and the effects of magnetic fields in the cosmos.
The Local Bubble is a massive, 1,000-light-year-wide hollow in space around our Sun. These so-called superbubbles are formed when massive stars explode into these bubbles and concentrate gas and dust — the fuel for future stars and planets — on their outer surfaces.
The scientists' overall understanding of superbubbles remains fragmentary. Researchers now have new information that could enhance their knowledge of the evolution of superbubbles, their impacts on star formation, and the habit of galaxies at large.
Scientists have created the first-of-its-kind map of a magnetic field in space. The group's investigation of our Local Bubble in 3D will help answer key questions about how magnetic fields interact in the cosmos.
Theo O'Neill, who was still an undergraduate at the University of Virginia, said putting together this 3D model of the Local Bubble will help us analyze superbubbles in new ways.
"Space is packed with these superbubbles that spark new stars and planets and influence the overall shapes of galaxies," says O'Neill, who graduated from UVA in December 2022 with a degree in astronomy-physics and statistics. "We can understand more about the exact mechanisms that drive the Local Bubble, in which the Sun lives today, and about superbubbles in general."
On Wednesday, Jan. 11, O'Neill presented the findings at the American Astronomical Society's 241st annual meeting in Seattle, Washington. The pre-print of the study is currently available on Authorea.com.
"From a basic physics perspective, we've long known that magnetic fields play a vital role in many astrophysical phenomena," Goodman says. "But studying these magnetic fields has been notoriously difficult. Eventually, new observational tools, computational methods, and enthusiastic colleagues tempt me back in. Today's computer simulations and all-sky surveys may just begin to integrate magnetic fields into our larger picture of how the universe works, from the motions of tiny dust grains to the dynamics of galaxy clusters."
The Local Bubble has emerged as a hot topic in astrophysics due to its proximity to the Sun and our Solar System. In 2020, Zucker, now of the Space Telescope Science Institute, Goodman, Joo Alves of the University of Vienna, and their team demonstrated that the Local Bubble's surface is the source of all nearby, young stars.
The new 3D magnetic field map was developed in part using data from Gaia, a European Space Agency (ESA) space-based observatory that monitored and measured stars' positions and movements, and that tracked the local concentrations of cosmic dust.
O'Neill and colleagues used these observations to supplement data from Planck, an ESA-led space telescope that conducted an all-sky survey from 2009 to 2013. The spacecraft was primarily built to study the Big Bang's relic light. The researchers also used a portion of Planck's observations to map the Local Bubble's magnetic field.
The polarized light that was observed was a result of magnetically aligned dust particles in space. The orientation of the magnetic field interacting with the dust particles.
Researchers mapped the magnetic field lines in this way to create a 2D model of the Earth's magnetic field projected on to the Local Bubble's surface. Second, that theories predicting that the magnetic field would be "swept up" in the bubble's surface are correct.
During his summer CfA internship, O'Neill completed the extensive geometrical research necessary to create the 3D magnetic field map.
The research team at Goodman is akin to pioneering mapmakers who created some of the first Earth's maps.
"To produce this first 3D map of a magnetic field, we've made some big assumptions; it's by no means a perfect image," she adds. "We will be able to improve the accuracy of our map and hopefully confirm what we're seeing."
If the magnetic field was indeed swept up into the bubble's surface, and if most of the polarization is produced there, the 3D view of magnetic whorls that emerged represent the neighborhood superbubble's magnetic field structure.
The research team further compared the resulting map to features along the Local Bubble's surface. Examples include the Per-Tau Shell, a massive spherical region of star formation, and the Orion molecular cloud complex, another well-known stellar nursery. Future research will investigate the interactions between magnetic fields and these and other surface features.
"We may begin to explore the effects of magnetic fields on stellar formation in superbubbles," says Goodman. "And, for that matter, we may discover how these fields influence other cosmic phenomena."
Goodman notes that there has been a tendency to overlook the effect of magnetic fields when designing simulations and theories where gravity, which is the primary force at play, is tolerable. Magnetism can be a fiendishly complex force to model.
Although understandable, magnetic fields' influence often overlooks a critical element regulating gas flow in the universe, such as gas flowing onto stars as they form, and flowing away from stars in powerful jets as they gather matter into a planet-forming disk. Magnetic fields can, nevertheless, be significant over time.
Goodman, O'Neill, and their colleagues are looking forward to learning more.
"I've had a fantastic experience doing this research at CfA and assembling something new and exciting with this 3D magnetic map," says O'Neill. "I hope this map will serve as a starting point for furthering our knowledge of the stellar structure."
The National Science Foundation, NASA, and the Gordon and Betty Moore Foundation provided financial assistance for this study.
The Milky Way's 3D Project
The 3D Milky Way project, which includes a collaboration with employees at the Hayden Planetarium at the American Museum of Natural History, will be presented at MilkyWay3D.org. Additional free software includes plot.ly and PyVista.
About the Harvard and Smithsonian Institution's Astrophysics Center
The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to explore—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe.