James Webb Space Telescope Observes Milky Way's Supermassive Black Hole Firing a Flare

Astronomers have utilized the James Webb Space Telescope to observe flares from Sagittarius A*, the supermassive black hole at the heart of our Milky Way galaxy, in a groundbreaking new way. The observations revealed mid-infrared flares for the first time, a significant advancement in understanding these cosmic phenomena.

The research team, led by Sebastiano von Fellenberg from the Max Planck Institute for Radio Astronomy in Bonn, Germany, made this discovery by bridging the gap between infrared and radio wavelengths. Previously, flares from Sgr A* had been documented primarily in the near-infrared regime, but this new mid-infrared data fills a critical void in the spectrum of Sgr A* flares.

Von Fellenberg noted that the mid-infrared flare resembles typical near-infrared flares, but differs significantly from radio observations, which do not show pronounced flare-like peaks. The team accomplished simultaneous observations at four different wavelengths using the Medium-Resolution Spectrometer of the Mid-Infrared Instrument aboard JWST.

This allowed them to measure the mid-infrared spectral index, enhancing their understanding of the mechanisms behind black hole flares. Notably, the phenomenon of synchrotron cooling was observed, indicating that high-speed electrons are losing energy by emitting synchrotron radiation, which powers the mid-infrared emissions.

The change in the mid-infrared spectral index over the flare's duration provided insights into the magnetic field strength around Sgr A*, a crucial parameter that had been poorly constrained in previous studies.

This new method of determining magnetic field strength is particularly beneficial because it requires fewer assumptions than previous methods. The research emphasizes the importance of the JWST in enabling these high-sensitivity observations, as ground-based telescopes struggle with mid-infrared wavelengths due to atmospheric interference.

The findings were first revealed in January 2025 and mark a significant milestone in the study of black hole behavior and the dynamics of our galaxy. As black holes consume surrounding matter, they can emit bursts of energy known as flares, but the exact causes of these flares remain a mystery.

The research not only enhances our understanding of Sgr A* but also showcases the capabilities of the James Webb Space Telescope in advancing astronomical research.