James Webb Telescope Reveals a Dazzling Light Show From the Milky Way’s Black Hole
Unpredictable bursts of light are pulsing from the debris surrounding Sagittarius A*, offering new insights into the mysterious behavior of the most massive object in our galaxy
The supermassive black hole at the heart of our galaxy, called Sagittarius A*, is more dynamic than previously thought, according to new observations made by NASA’s James Webb Space Telescope (JWST). The infrared observatory has captured a nonstop, chaotic light show of flickers and dramatic flares from the gas and dust captured by the black hole’s enormous gravity.
“It is always bubbling with activity and never seems to reach a steady state,” Farhad Yusef-Zadeh, an astrophysicist at Northwestern University and lead author of the study published Tuesday in The Astrophysical Journal Letters, says in a statement. “We observed the black hole multiple times throughout 2023 and 2024, and we noticed changes in every observation. We saw something different each time, which is really remarkable.”
Sagittarius A*—pronounced “Sagittarius A star” and called Sgr A* for short—is located about 26,000 light-years from Earth. It has long been known for its energetic activity, but JWST’s unique capabilities have allowed scientists to observe it with unprecedented detail. The telescope’s Near-Infrared Camera (NIRCam) tracked the black hole for a total of 48 hours over the course of a year, observing five to six large flares per day with smaller sub-flares in between.
“In our data, we saw constantly changing, bubbling brightness,” Yusef-Zadeh says in the statement. “And then boom! A big burst of brightness suddenly popped up. Then, it calmed down again. We couldn’t find a pattern in this activity.”
The new results offer more to how our galaxy’s black hole changes over time, as Tuan Do, an astrophysicist at the University of California, Los Angeles, who was not involved in the study, tells CNN’s Ashley Strickland. “This is what makes observations of the galactic center so exciting, even though we’ve stared at this spot in the sky for decades now.”
These flares originate from Sgr A*’s accretion disk—a swirling mass of gas and dust that’s slowly spiraling toward the black hole, drawn in by its immense gravitational force. While black holes themselves are invisible, the hot gas surrounding them emits intense radiation. This radiation often takes the form of sudden bursts or more subtle flickers, caused by the turbulent nature of the accretion disk.
“Blobs of gas are bumping into one another, and in some cases being forced or compressed together by the strong magnetic fields that exist within the disk—somewhat similar to what happens in solar flares,” study co-author Howard Bushouse, an astrophysicist at the Space Telescope Science Institute, tells Will Dunham of Reuters.
Despite being relatively close to Earth in astronomical terms, Sgr A* has been difficult to study because of the dense dust clouds that surround the center of the Milky Way. However, JWST’s infrared capabilities allow it to peer through this cosmic fog, revealing the continuous, rapid fluctuations in brightness around the black hole.
“Most previous observations, done from both the ground-based and space-based telescopes, were limited to only being able to observe Sgr A* for a few hours at a time or were limited in their sensitivity and hence only detected the occasional brightest flares,” Bushouse says to Reuters.
The data from these new, extended observations suggest the black hole’s behavior is highly variable. Flares seem to occur randomly, with no predictable pattern, and the size of the bursts ranges from small flickers to enormous eruptions. Some of the fainter glows last for months on end.
Researchers suspect these variations are caused by disturbances within the accretion disk, where hot, electrically charged gas (known as plasma), is squeezed and releases bursts of radiation. The brightest blasts might be caused by magnetic fields colliding, per the statement, which sends fast-moving particles tearing through the universe at nearly the speed of light.
In addition to the flares, the researchers also discovered an unexpected delay between changes in brightness when observing at two different wavelengths of light. This lag, lasting from a few seconds to 40 seconds, offers important clues to what’s occurring near the black hole.
One possible explanation is that the fast-moving particles gradually lose energy during the flare, with energy being lost more rapidly at shorter wavelengths compared to longer ones. This behavior is typical for particles moving along magnetic field lines, per the statement.
These discoveries are just the beginning. With more observations, the astronomers hope to refine their understanding of how black holes interact with their surroundings and, in particular, how they affect galaxy formation. Yusef-Zadeh recently submitted a proposal for a 24-hour uninterrupted observation of Sgr A* with JWST, which could help reduce noise in the data and provide an even clearer picture of the structure.
Mark Wardle, an astrophysicist at Macquarie University in Australia and a co-author of the study, tells Ellen Phiddian of the Australian Broadcasting Corporation he is looking forward to seeing more research in this area. Further observations, he adds, are needed to help scientists better understand how gas behaves around the black hole.
“We’ve really only had a first pass of this,” Wardle says. “There’s so much information… we haven’t explored yet.”