The core of the Milky Way (also known as the Galactic Center), the region around which the rest of the galaxy revolves, is a strange and mysterious place. This is where the Supermassive Black Hole (SMBH) is located, which powers the compact radio source called Sagittarius A *. It is also the most compact region in the galaxy, with an estimated 10 million stars within 3.26 light years of the Galactic Center.
Using data from the Chandra X-ray Observatory and the MeerKAT radio telescope, NASA and the National Research Foundation (NSF) of South Africa created a mosaic of the center of the Milky Way. By combining images captured in the X-ray and radio wavelength ranges, the resulting panoramic image succeeds in capturing the filaments of overheated gas and magnetic fields that (when visualized) show the complex energy network in the center of our galaxy.
This new panorama builds on previous surveys made by Chandra and other telescopes of the center of our galaxy. Because of the intense brightness caused by so many star clusters, scientists can only study the region at depth by observing it at different wavelengths. This latest version includes views of the area above and below the plane of the galaxy, the central disk of the Milky Way, showing the large clouds of gas protruding outward.
Image of the Galactic Center, visualized in X-ray (left), radio (middle) and composite with annotations (right). Photo credit: X-ray: NASA / CXC / UMass / QD Wang; Radio: NRF / SARAO / MeerKAT)
This makes it possible to fully recognize special features emanating from the Galactic Center, such as radio wave filaments running vertically and horizontally. As you can see on the above slides (broken down by wavelength), different types of radiation are shown in different colors. The X-ray sources observed by Chandra (left) are shown in orange, green, blue and purple (for different X-ray energies), while the radio sources observed by MeerKAT (center) are shown in purple and gray.
The main features of the image are shown in an annotated mosaic (right), including the radio source Sagittarius A *. This feature is close to the center in both X-ray and radio visualization and is the strongest source of the energies observed. Another interesting feature is the slender thread-like features shown in red boxes (labeled G0.17-0.41 and G359.55 + 0.16).
These threads consist of intertwined X-ray and radio waves that extend for several light years perpendicular to the plane of the galaxy. Both have been the subject of research, the most recent of which is from the University of Massachusetts at Amherst. After observing G0.17-0.41, Professor Daniel Wang and his colleagues conclude that threads like these are connected to one another by thin magnetic field strips.
These streaks could have formed through magnetic reconnection, a phenomenon similar to what drives energetic particles from the sun into the solar system (also known as solar wind or “space weather”). In this case, the weather is determined by volatile phenomena near the Galactic Center, such as supernovae, densely packed stars ejecting plasma clouds, and eruptions of matter from regions near Sagittarius A *.
Mosaic image of the Galactic Center with annotations. Photo credit: X-ray: NASA / CXC / UMass / QD Wang; Radio: NRF / SARAO / MeerKAT)
As a result, magnetic fields that are oriented in different directions collide and twist around each other, resulting in the unusual structures we see here. Based on the picture, these magnetic threads appear to be appearing at the outer boundaries of the large hot gas plumes, suggesting that it could be the gas in these clouds that is driving the magnetic field to collide and creating the threads.
These hot gas clouds, which extend about 700 light years above and below the galaxy level, are also examined by Wang and his colleagues in their study. In theory, these clouds of plasma and energetic particles could represent outflows on a galactic scale, much like particles drifting away from the sun. It is also possible that they are being heated by supernovae and the many recent magnetic reconnections near the center of the galaxy.
A detailed study of these threads will teach us much more about the type of space weather astronomers have observed in the central region of our galaxy. For example, you might discover that magnetic reconnection events play an important role in warming the interstellar medium (the gas and dust that exists between stars). It is also possible that they are responsible for accelerating particles to create cosmic rays and form new stars.
The panorama also reveals other wonders in the Galactic Center, such as the arcs, the quintuplet, and other star clusters (DB00-58, DB00-6, and 1E 1743.1-28.43), the Sagittarius C Molecular Cloud, and the Cold Gas Cloud, all shown in purple circles and ellipses . Watch the video below (courtesy of NASA’s Chandra X-ray Center) for more details on this panorama and its insights into the core region of our galaxy:
Further reading: NASA, Chandra X-ray Observatory