Astronomers Observe the Reawakening of the Active Galactic Nucleus in J1007+3540

Astronomers have recently documented a rare and significant event within the galaxy J1007+3540, observing the periodic "restarting" of its Active Galactic Nucleus (AGN) after an extensive period of dormancy. A comprehensive study, which appeared in the January 2026 issue of the Monthly Notices of the Royal Astronomical Society, provides a detailed account of this central supermassive black hole’s return to an active state. Utilizing radio imaging data from the LOFAR and uGMRT interferometers, researchers confirmed that the black hole has "re-ignited" following an estimated silence lasting approximately one hundred million years.

This newly emerged radiation is characterized by a brilliant and compact internal jet that is currently piercing through a surrounding "cocoon" composed of ancient, fading plasma. Such a feature is a hallmark of an episodic AGN, where the black hole undergoes distinct phases of activity. These plasma jets, which extend nearly one million light-years into space, show evidence of substantial distortion and compression. This structural warping is the result of immense external pressure exerted by the hot gas permeating the galaxy cluster where the host galaxy resides. Dr. Surajit Paul, representing the Manipal Centre for Natural Sciences (MCNS), emphasized that J1007+3540 serves as one of the most striking examples of how an episodic AGN interacts with its surrounding cluster environment.

The investigative team, spearheaded by Shobha Kumari of Midnapore City College, pointed out that the uniqueness of J1007+3540 lies in its history of multiple eruptions. This suggests that the galaxy's central engine cycles between active and quiescent states over vast cosmic timescales. While previous reports from 2023 indicated that the AGN had remained in an "off" state for at least two hundred days, the fresh data from 2026 provides definitive proof of its current resurgence. This phenomenon offers a rare window for scientists to analyze the evolution of radio jets and the specific ways in which dense cluster environments influence the morphology of these massive cosmic outflows.

Beyond identifying the new phase of activity, the observations conducted with LOFAR and uGMRT were instrumental in capturing "relic" structures from the galaxy's past. These aged, dimming lobes represent the remains of previous eruptions and can remain detectable at low radio frequencies for hundreds of millions of years after the AGN's energy supply has ceased. Specifically, LOFAR imagery revealed a notably compressed northern lobe, where the plasma has been pushed sideways by the resistance of the surrounding cluster gas. Complementary data from uGMRT further demonstrated that this compressed region is populated by older particles that have lost much of their energy, providing direct evidence of the cluster's physical impact on the galaxy's emissions.

Looking ahead, the research group has outlined plans to conduct high-resolution observations using the VLA and ALMA telescopes toward the end of 2026. These upcoming efforts will focus on creating a detailed map of the newly launched jets and establishing a more precise timeline for the galaxy's activity cycles. The study of dynamic systems like J1007+3540 is vital for understanding the broader influence of supermassive black holes on the growth and evolution of galaxies. This is particularly true in the high-pressure environments of galactic clusters, where such observations help refine theoretical models of black hole behavior as they transition through active and dormant phases.