New Delhi: In a groundbreaking discovery, scientists from the Indian Space Research Organisation (ISRO) and the Indian Institute of Technology (IIT) Guwahati have identified a puzzling pattern of X-ray signals emitted by a black hole nearly 28,000 light-years away, offering new insights into the dynamics of these enigmatic cosmic giants.
The black hole, named GRS 1915+105, was studied using India’s space observatory AstroSat in collaboration with researchers from Haifa University, Israel.
Observations revealed that its X-ray brightness oscillates between bright and dim phases, each lasting several hundred seconds—a phenomenon that had never been understood in such detail until now.
According to the study, published in the Monthly Notices of the Royal Astronomical Society, these phases are marked by a striking difference: rapid flickers of X-rays occur only during the high-brightness phase, repeating at an astonishing rate of about 70 times per second (70 Hz), while disappearing completely during the dim phase.
Dr. Anuj Nandi from ISRO’s U. R. Rao Satellite Centre said the research provides direct evidence for the origin of this flickering.
“We have linked these signals to modulations in the corona—the hot plasma surrounding the black hole,” he explained.
Prof. Santabrata Das from IIT Guwahati elaborated that during bright phases, the corona becomes compact and significantly hotter, intensifying the flickering effect.
In contrast, during dim phases, it expands and cools, causing the flickers to vanish.
This dynamic behaviour suggests the corona is not a fixed structure but one that oscillates with changes in the flow of gas spiralling into the black hole.
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The discovery marks the first evidence of such rapid X-ray flickering associated with changes in the black hole’s corona, made possible by AstroSat’s high-precision instruments.
Researchers believe this breakthrough could reshape our understanding of how black holes grow, release energy, and influence their cosmic environments.
“This study gives us a clearer picture of the extreme conditions—immense gravity and searing heat—that govern matter near a black hole’s edge,” the authors noted.
The findings could also help explain the role of black holes in the evolution of galaxies, as their energy output impacts surrounding matter and star formation over cosmic timescales.
