A black hole dormant for 100 million years just erupted across a million light-years

A supermassive black hole has exploded back to life inside galaxy J1007+3540, unleashing jets of magnetized plasma that now stretch across nearly a million light-years of space. Astronomers describe the eruption as a “cosmic volcano” — and say it reveals something fundamental about how black holes govern the fate of entire galaxies over deep time.

The black hole at J1007+3540’s core has done this before. Radio images captured using the Low Frequency Array (LOFAR) in the Netherlands and the upgraded Giant Metrewave Radio Telescope (uGMRT) in India show two distinct layers of history frozen in space: a vast outer halo of fading, ancient plasma from a previous eruption hundreds of millions of years old, and nestled inside it, a compact, brilliantly bright jet of fresh material — unmistakable evidence the engine has restarted. The gap between those two episodes represents roughly 100 million years of complete silence.

To put that dormancy in context: when this black hole last went quiet, non-avian dinosaurs had not yet gone extinct. Whatever triggered the shutdown, it lasted longer than the entire geological age of the Himalayas.

What makes J1007+3540 especially compelling is the environment the jets are fighting through. The galaxy sits inside a massive cluster filled with scorching gas, and that gas is pushing back hard. The galaxy’s northern lobe is bent, compressed, and dramatically distorted — warped by the crushing external pressure. Researchers describe it as watching a high-pressure fire hose aimed at a brick wall: the relativistic plasma sprays backward, leaving a chaotic backflow signature that no standard galaxy evolution model anticipated.

This struggle matters far beyond aesthetics. When black holes erupt, they pump enormous kinetic energy into surrounding gas — energy that can prevent that gas from cooling and collapsing into new stars. The scale and timing of each eruption determine how thoroughly a galaxy grows, stalls, or transforms. J1007+3540’s host galaxy is composed largely of stars formed over 12 billion years ago, yet it is still generating new stars at a rate exceeding 100 solar masses per year. The cycle of construction and destruction is far from over.

The team, led by Shobha Kumari of Midnapore City College in India, assembled the radio maps by pairing LOFAR’s sensitivity to faint, diffuse emission with uGMRT’s sharper resolution. The combination allowed them to distinguish the ancient plasma debris from the freshly ignited inner jets within the same observation.

Important caveats apply. Estimating the age of plasma lobes depends on models of how rapidly electrons lose energy over cosmic time, and those models carry significant uncertainty at the scales involved. The 100-million-year dormancy figure is a calculated interval, not a directly clocked one — future observations may revise it. The study also examines a single galaxy; how commonly black holes elsewhere follow a similar on-off duty cycle remains an open question.

The team has announced plans for higher-resolution follow-up observations targeting J1007+3540’s core, with the goal of tracking in real-time — on an astronomical timescale — how the newly restarted jets propagate through the cluster medium. The research appeared in Monthly Notices of the Royal Astronomical Society.