Using data from NASA’s retired Spitzer Space Telescope, scientists have gained new insights into the eating habits of supermassive black holes at the centers of galaxies across the universe. These black holes often fluctuate in brightness from massive clumps of cosmic material that fall into them.
However, this is not true for the black holes located at the centers of the Milky Way and Andromeda galaxies. Instead, they remain fairly quiet and rarely change in brightness. To find the cause of the reduced activity around black holes, a new study used observations from Spitzer and Hubble to model the black hole and the material surrounding it at the center of the Andromeda galaxy.
In images from Spitzer, long streams of dust stretching thousands of light-years can be seen streaming into the supermassive black hole at the center of the Andromeda galaxy – the closest major galaxy to Earth, located about 2.5 million light-years away. away.
As gas and cosmic dust fall into supermassive black holes, such as the one located in Andromeda, the material heats up and begins to glow, creating light shows around the black hole that can outshine entire galaxies. However, this material is not absorbed immediately. Instead, material is consumed in clumps that vary in size, causing the black hole’s brightness to fluctuate.
Close-up view of the center of the Andromeda galaxy, taken by the Spitzer Space Telescope. The dotted blue lines highlight the path of the two streams pouring into the black hole at the center of the galaxy. (Credit: NASA/JPL-Caltech)
Interestingly, the supermassive black holes located at the center of the Milky Way and Andromeda are among the quietest black holes known in the universe when it comes to consuming (or “eating”) cosmic material. When light is emitted from black holes, the light does not change significantly in brightness, which may mean that the black holes are fed by a small, steady stream of cosmic material rather than clumps of material of varying sizes.
Earlier this year, a team of scientists applied the hypothesis of a black hole feeding a small steady stream of cosmic material to the Andromeda galaxy and simulated how the gas and dust around the Andromeda black hole would behave as it passes times. The simulation revealed that a small disk of hot gas could form near the black hole and continuously provide the black hole with a stream of cosmic material. The disk can continuously provide material due to the replenishment of the disk by multiple streams of gas and dust.
However, the team also found that the currents that recharge the disk must remain within a certain size and flow rate. If they become too large or too small, the material will fall into the black hole in clumps of different sizes, causing the black hole to fluctuate in brightness, which the Milky Way’s black holes and of Andromeda.
When looking back at previous observations of Andromeda by NASA’s Hubble Space Telescope and Spitzer, the scientists found dust spirals that fit the constraints highlighted by the simulation. Using these images, the team concluded that the spirals were indeed feeding the supermassive black hole at the center of Andromeda. This result also means that a similar process is likely to occur in the center of the Milky Way, given that the two black holes exhibit similar behavior and characteristics.
This is an excellent example of scientists re-examining archival data to discover more about galaxy dynamics by comparing it with the latest computer simulations. We have 20 years of data that show us things we didn’t recognize in them when we first collected them, said co-author Almudena Prieta of the Canary Islands Institute of Astrophysics and the University Observatory of Munich.
Image of the center and outer regions of the Andromeda galaxy taken by Hubble in visible light. (Credit: NASA/ESA/J. Dalcanton (University of Washington, USA)/BF Williams (University of Washington, USA)/LC Johnson (University of Washington, USA)/PHAT team/R. Gendler)
As mentioned, images from Spitzer were used to confirm the scientists’ hypothesis. Spitzer was launched in August 2003 atop a Delta II from Cape Canaveral Air Force Station and was the third telescope dedicated exclusively to observing the infrared universe. The joint NASA, European Space Agency and Canadian Space Agency James Webb Space Telescope is another telescope that observes exclusively in the infrared. Infrared observation has many advantages, notably that it gives scientists the ability to see through the thick layers of dust that are present in galaxies and other cosmic objects, as well as the ability to see the very early universe.
Spitzer’s observations of Andromeda were carried out using different wavelengths, each revealing different features of the galaxy such as stars and dust structures. By splitting the wavelengths and looking only at the dust, scientists were able to see the galaxy’s “skeleton,” or regions where gas has coalesced and cooled, creating stellar nurseries where new stars can form.
Seeing the galaxy this way surprised scientists. One surprise was that Andromeda is dominated by a large ring of dust rather than the conventional separate arms surrounding the galactic center. Additionally, a large hole was found within the ring where a dwarf galaxy was passing through.
Infrared images from Spitzer showing dust inside Andromeda. (Credit: NASA/JPL-Caltech/University of Arizona)
Although Spitzer has a wider field of view than Hubble, the telescope still had to take about 11,000 images of the galaxy to create the image used in the study.
The team’s results were published inThe Astrophysical Journal.
(Main image: The Andromeda Galaxy seen in infrared by the Spitzer Space Telescope. Credit: NASA/JPL-Caltech/University of Arizona)
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