The Milky Way is our galaxy, but how well do we really know it? A team led by Villanova University researchers as part of a NASA-funded project has obtained a never-before-seen image of the central engine at the heart of our galaxy.
A new map of this central region of the Milky Way, which took four years to put together, reveals the relationship between magnetic fields at the heart of our galaxy and the cold dust structures that live there. This dust forms the building blocks of stars, planets, and eventually life as we know it. The Milky Way’s central engine drives this process.
This means that a clearer picture of dust and magnetic interactions will provide a better understanding of the Milky Way and our place within it. The team’s findings have implications beyond our galaxy, offering glimpses into how dust and magnetic fields interact in the central engines of other galaxies.
Relating to: How do we know what the Milky Way looks like?
Understanding how stars and galaxies form and evolve is a vital part of the origin story of life; But until now, the interaction of dust and magnetic fields in this process had been somewhat overlooked, especially in our own galaxy.
“The center of the Milky Way and much of the space between stars is filled with a lot of dust, and this is important for the life cycle of our galaxy,” David Chuss, research team leader and professor of physics at Villanova University, told Space. com. “What we were looking at was light emitted from these cold dust grains, produced by heavy elements formed in stars and dispersed when stars died and exploded.”
A complex picture of the Milky Way magnetic fields
At the heart of the Milky Way lies a dust-filled region called the central molecular region, which is estimated to be 60 million solar masses. The temperature of this vast dust reservoir is around minus 432.7 degrees Fahrenheit (minus 258.2 degrees Celsius). This is just a few degrees above absolute zero (minus 460 Fahrenheit), the hypothetical temperature at which all atomic motion would cease.
Also at the heart of the Milky Way is a hotter gas that has been stripped of its electrons, or “ionized,” and exists as a state of matter called “plasma.”
“Radio wave observations of this region include these beautiful vertical elements tracking magnetic fields in the hot, ionized plasma component at the center of the Milky Way,” Chuss said. “We tried to understand how this relates to the cold powder component.
The team also wanted to know how this cold dust aligned with magnetic fields at the heart of the Milky Way; This would also reveal how these magnetic fields are directed. This orientation is called “polarization”.
Chuss and his colleagues received funding from NASA to investigate this dusty central region using the Stratospheric Observatory for Infrared Astronomy (SOFIA), an Earth-circling telescope at an altitude of 45,000 feet (13,716 meters) aboard a Boeing 747 aircraft.
The project’s Far Infrared Polarimetric Wide Field CMZ Survey (FIREPLACE) created an infrared map spanning nearly 500 light-years across the center of the Milky Way over the course of nine flybys.
Using measurements of the polarization of radiation emitted from dust aligned with magnetic fields, the team revealed the complex structure of these magnetic fields. This was then overlaid on a three-colour map showing hot dust in pink and cool dust clouds in blue. The image also shows radio wave emitting filaments in yellow.
“It’s a journey, not a destination, but we found that it’s a very complex thing. The directions of the magnetic field vary throughout the clouds at the center of the Milky Way,” Chuss explained. “This is the first step in trying to understand how the field we see in radio waves along large organized filaments might be related to the remaining dynamics of the center of the Milky Way.”
Chuss explained that this complex picture of magnetic fields is something he and the FIREPLACE team expected to see with the new SOFIA map; The observations were consistent with previous smaller-scale infrared and radio wave observations made at the heart of the Milky Way. However, where this new map really comes into its own is the sheer scale. It manages to reveal some areas that have never been mapped before. The fine details inside are also dazzling.
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“I think we have a lot of work to do here to come to a final conclusion. One of the things I think is interesting is that some of the fields appear to be in the same direction as the filaments in the radio waves. “Some of these appear to be consistent with the orientation of the dust further into the disk,” Chuss said. “With the large-scale field in the disk of our galaxy “It’s a promising clue that the vertical field we notice at the center of the Milky Way may be connected.”
He and his team will continue analyzing SOFIA data over the next two years, and he hopes this work will inspire theorists to come up with some new models to explain what’s happening at the heart of our galaxy.
A preprint version of the SOFIA data is published in the arXiv paper repository.