Flickering Light Show: Milky Way's Supermassive Black Hole Emits Continuous Flares

Flickering Light Show: Milky Way's Supermassive Black Hole Emits Continuous Flares
by Clarence Oxford
Los Angeles CA (SPX) Feb 20, 2025

The Milky Way's central supermassive black hole, Sagittarius A*, is proving to be a relentless source of cosmic activity, continuously producing bursts of light with no apparent pattern, according to new findings by astrophysicists using NASA's James Webb Space Telescope (JWST).

A team led by Northwestern University conducted the longest and most detailed observational study of Sagittarius A* to date. Their results reveal a non-stop sequence of flares and flickers emanating from the swirling disk of gas and dust encircling the black hole. The activity occurs over varying timescales-ranging from brief, faint flashes lasting mere seconds to intense, dazzling outbursts occurring daily, along with prolonged surges that persist for months.

Published in The Astrophysical Journal Letters, the research provides fresh insights into black hole behavior, shedding light on their interaction with surrounding matter and offering new perspectives on the evolution of our galaxy.

"Flares are a common feature of supermassive black holes, but Sagittarius A* stands out due to its constant variability," explained lead researcher Farhad Yusef-Zadeh from Northwestern University. "Throughout 2023 and 2024, our observations showed something new every time, with no stable state ever reached."

Yusef-Zadeh, a professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences, collaborated with an international team, including researchers from the Space Telescope Science Institute, NASA, Macquarie University, Harvard and Smithsonian, and the National Radio Astronomy Observatory.

A Chaotic Light Display

Using JWST's Near-Infrared Camera (NIRCam), the researchers observed Sagittarius A* for a total of 48 hours over the span of a year, capturing 8-to-10-hour segments in each session. The telescope's ability to observe two infrared wavelengths simultaneously provided an unprecedented look at the black hole's fluctuating luminosity.

While flares were anticipated, the sheer frequency and unpredictability of the emissions took scientists by surprise. The accretion disk produced multiple large flares daily, interspersed with a series of smaller bursts, resembling a random fireworks display.

"Our data showed a continuously shifting brightness pattern," Yusef-Zadeh noted. "Suddenly, a bright burst would appear, followed by a return to a more subdued state. We couldn't detect any repeating sequence-it all seemed random."

Unraveling the Mystery: Two Possible Mechanisms

The team proposes that two distinct processes may be responsible for the variations in flare intensity and duration. Short, faint flickers could arise from minor disturbances in the accretion disk, where turbulence compresses plasma and triggers brief bursts of radiation, akin to solar flares.

In contrast, the brighter, more sustained outbursts likely stem from magnetic reconnection events, where magnetic field lines collide and release high-energy particles moving near the speed of light. These accelerated particles produce the luminous emissions detected by JWST.

"Magnetic reconnection acts like a cosmic spark, similar to how static electricity discharges energy," Yusef-Zadeh explained.

Observing in Two Wavelengths

By capturing data at 2.1 and 4.8 microns simultaneously, the team made another intriguing discovery: a slight time delay between the two wavelengths, with shorter wavelengths brightening just seconds before the longer ones.

"This is the first time we've observed such a time lag at these infrared wavelengths," said Yusef-Zadeh. "It suggests that particles lose energy over time, decaying more quickly at shorter wavelengths before transitioning to longer wavelengths-a phenomenon expected for particles spiraling around magnetic field lines."

Aiming for a Longer Look

To refine their understanding, the researchers have proposed an uninterrupted 24-hour observation of Sagittarius A* with JWST. By extending the monitoring period, they hope to reduce background noise and identify potential patterns in the variability.

"When studying weak flares, signal noise becomes a challenge," Yusef-Zadeh said. "A continuous 24-hour observation would enhance our ability to detect subtle features, possibly revealing periodic behavior or confirming their randomness."

Research Report:Non-stop variability of Sgr A* using JWST at 2.1 and 4.8 micron wavelengths: Evidence for distinct populations of faint and bright variable emission