Scientists have unlocked the 3D structure of molecular clouds in the Milky Way’s center, using a groundbreaking X-ray technique.
These cosmic clouds, vital for star formation, were illuminated by past outbursts from the supermassive black hole, Sagittarius A*. By analyzing how X-ray flares interact with these clouds, astronomers pieced together a detailed cosmic map, revealing insights into the turbulent heart of our galaxy.
Mapping the Heart of the Milky Way
This image showcases a study that uses decades of data to explore the 3D structure of molecular clouds at the center of the Milky Way. The panoramic graphic combines multiple types of observations: radio data from the Submillimeter Array (green), infrared data from the Herschel Space Telescope (red) and the Spitzer Space Telescope (blue), and an inset featuring X-ray data from NASA’s Chandra X-ray Observatory.
Illuminating Molecular Clouds with X-Rays
For the first time, researchers have mapped molecular clouds — dense regions where stars form — in three dimensions within one of the most extreme environments in our galaxy. They studied past flaring events from the Milky Way’s supermassive black hole, Sagittarius A* (Sgr A*), which sits at the galactic center. This region is highly turbulent, with gas temperatures, densities, and motion about ten times more intense than elsewhere in the Milky Way. Occasionally, inflowing gas gets pulled into Sgr A*, triggering powerful X-ray flares that radiate outward.
These X-ray flares interact with molecular clouds through a process called fluorescence. As the X-ray light moves through space, it illuminates different layers of the clouds over time, much like an X-ray scan, revealing their hidden structure.
New X-Ray Tomography Reveals Hidden Structures
The team developed a new X-ray tomography method to make 3D maps of two Galactic Center molecular clouds dubbed the “Stone” and the “Sticks” clouds. These maps are the first-ever renderings of Galactic Center molecular clouds in three spatial dimensions. They used Chandra data spanning two decades to create their 3D models of the Stone and Sticks molecular clouds.
While astronomers typically only see two spatial dimensions of objects in space, the X-ray tomography method allows us to measure the third dimension of the cloud because the X-rays illuminate individual slices of the cloud over time.
Decoding Galactic Echoes to Measure Time
The researchers also used data from the Submillimeter Array and Herschel Space Observatory to compare the structures seen in the X-ray echoes to those seen in other wavelengths. Because X-ray data is not collected continuously, there are some structures seen in submillimeter wavelengths that are not seen in X-rays. However, these “missing” structures allowed the researchers to constrain the duration of the X-ray flare event illuminating the Stone Cloud. They determined that the X-ray flare couldn’t have been much longer than four to five months.
These results were presented by Danya Alboslani (University of Connecticut) at the 245th meeting of the American Astronomical Society meeting in National Harbor, MD.
Explore Further: X-Ray Echoes Unveil the Hidden 3D Landscape of Our Galaxy’s Heart
References:
“3D MC I: X-ray Tomography Begins to Unravel the 3-D Structure of a Molecular Cloud in our Galaxy’s Center” by Samantha W. Brunker, Cara Battersby, Danya Alboslani, Maïca Clavel, Daniel L. Walker, Dani Lipman, H Perry Hatchfield and Régis Terrier, 13 January 2025, Astrophysics > Astrophysics of Galaxies.
arXiv:2501.07717
“3D MC II: X ray echoes reveal a clumpy molecular cloud in the CMZ” by Danya Alboslani, Cara Battersby, Samantha Brunker, Maïca Clavel, Daniel Walker and Dani Lipman, 13 January 2025, Astrophysics > Astrophysics of Galaxies.
arXiv:2501.07669
NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
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