NASA’s Spitzer Reveals Supermassive Black Hole Eating Habits of Andromeda

These images of the Andromeda galaxy use data from NASA’s retired Spitzer Space Telescope. The top image shows several wavelengths that reveal stars, dust, and star-forming regions. The bottom image shows only the dust, so it’s easier to see the underlying structure of the galaxy. Credit: NASA/JPL-Caltech

NASAImages from the Spitzer Space Telescope show the streams of dust feeding the supermassive Black hole in Andromeda, revealing how these black holes can feed continuously without significant fluctuations in light. Recent studies using computer models and archival data support this finding.

Images from NASA’s retired Spitzer Space Telescope show streams of dust thousands of light-years long toward the supermassive black hole at the heart of the Andromeda galaxy. It turns out that these currents can help explain how black holes, billions of times more massive than our Sun, satisfy their big appetites but remain “quiet” eaters.

As supermassive black holes swallow gas and dust, the material heats up just before it falls in, creating an incredible light show – sometimes brighter than an entire galaxy full of stars. As the material is consumed in clumps of varying sizes, the black hole’s brightness fluctuates.

But the black holes at the center of the Milky Way (Earth’s home galaxy) and Andromeda (one of our closest galactic neighbors) are among the quietest eaters in the universe. How much light they emit does not vary significantly in brightness, indicating that they consume a small but steady stream of food, rather than large clumps. The currents approach the black hole bit by bit and in a spiral, much like water swirls down a drain.

Hunting for Andromeda’s food source

A study published earlier this year took the hypothesis that a silent supermassive black hole feeds on a steady stream of gas and applied it to the Andromeda galaxy. Using computer models, the authors simulated how the gas and dust near the supermassive black hole in Andromeda might behave over time. The simulation showed that a small disk of hot gas could form near a supermassive black hole and continuously feed it. The disk could be replenished and maintained by numerous streams of gas and dust.

But the researchers also found that these currents must remain at a certain size and flow rate; otherwise, the matter would fall into the black hole in irregular clumps, causing the light to fluctuate more.

This close-up view of the center of the Andromeda Galaxy, taken by NASA’s retired Spitzer Space Telescope, is marked by blue dotted lines that highlight the path of two dust streams flowing toward the supermassive black hole at the center of the galaxy (indicated by the purple dot). Credit: NASA/JPL-Caltech

When the authors compared their findings with data from Spitzer and NASA’s Hubble Space Telescope, they found dust spirals previously identified by Spitzer that fit within these constraints. From this, the authors concluded that the spirals are feeding Andromeda’s supermassive black hole.

“This is a great example of how scientists re-evaluate archival data to reveal more about galaxy dynamics by comparing it with the latest computer simulations,” said Almudena Prieto, an astrophysicist at the Institute of Astrophysics of the Canary Islands and the University Observatory of Munich. co-author of a study published this year. “We have 20-year-old data telling us things we didn’t know about it when we first collected it.”

A deeper look at Andromeda

Launched in 2003 and operated by NASA’s Jet Propulsion Laboratory (JPL), Spitzer studied the universe in infrared light, which is invisible to the human eye. Different wavelengths reveal different features of Andromeda, including hotter sources of light such as stars and cooler sources such as dust.

By separating these wavelengths and looking at the dust itself, astronomers can see the “skeleton” of a galaxy – the places where gas has clumped together and cooled, sometimes forming dust, which creates the conditions for star formation. This look at Andromeda revealed a few surprises. For example, although it is a spiral galaxy like that Milky Way, Andromeda is dominated by a large dust ring rather than distinct arms circling its center. The images also revealed a secondary hole in one part of the ring that the dwarf galaxy was passing through.

Andromeda’s proximity to the Milky Way means it appears larger than other galaxies from Earth: Seen with the naked eye, Andromeda would be about six times the width of the Moon (about 3 degrees). Even with a field of view wider than Hubble’s HST, Spitzer had to take 11,000 images to create this comprehensive picture of Andromeda.

More about the mission

JPL managed the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington until the mission ended in January 2020. Science operations were conducted at the Spitzer Science Center at Caltech. Spacecraft operations were based at Lockheed Martin Space in Littleton, Colorado. The data are archived in the Infrared Science Archive operated by IPAC at Caltech. Caltech manages JPL for NASA.