For the first time, two black holes have been captured circling each other, proving the long-held assumption of the existence of the cosmic duo.
Using an extraordinary network of telescopes, an international team of astronomers, including one orbiting halfway to the Moon, Mauri Valtonen and his associates, including Alok C Gupta, Shubham Kishore, and A Gopakumar, spotted a radio image of quasar OJ287, a distant galaxy powered by not one but two black holes orbiting each other every 12 years, locked in a cosmic dance, according to a Ministry of Science and Technology statement on Friday.
“Seeing two black holes in orbit is more than a stunning image. It is a window into the future of our universe. When black holes eventually collide, they release titanic ripples in spacetime called gravitational waves, the very ripples that observatories like LIGO and Virgo have detected. Studying OJ287 gives scientists a natural laboratory for understanding how such cataclysmic events unfold,” the Ministry said.
The findings in which ARIES, an autonomous institute of the Department of Science and Technology (DST), played a crucial part were published in the Astrophysical Journal on October 9.
For decades, astronomers suspected this cosmic duo existed because of the quasar’s rhythmic flickering, a pattern first traced back to 19th-century photographs. The periodic behaviour was discovered in 1982, and since then, thousands of astronomers have followed it to get a complete picture of its orbital motion.
The final solution of the orbit was achieved in two publications published in 2018 in the Astrophysical Journal of the American Astronomical Society and in 2021 in the Monthly Notices of the Royal Astronomical Society of the United Kingdom. The leading author of these papers was Lankeswar Dey of the Tata Institute of Fundamental Research (TIFR) in Mumbai, supervised by Professor Gopakumar of that institute and partly by Valtonen of the University of Turku, Finland.
The only thing to be proven then was that the binary model, which tells exactly where to find the two black holes with respect to each other at any time, was correct, and whether they were bright enough to be seen, and if there is an image of high enough resolution that they can be separated spatially.
The breakthrough came when the astronomers, who were able to monitor OJ287 with NASA’s TESS satellite in late 2021, discovered a huge brightening in just 12 hours, corresponding to the extra brightness of some hundred galaxies. OJ287 faded away equally fast, and it was confirmed by ground-based observations by a number of telescopes.
In the meantime, a radio image of OJ287 was produced, which had the unprecedented resolution and showed both black holes, as reported by Valtonen and his associates.
The image revealed not one but two distinct points of radio emission. Just as predicted, these were the two black holes of OJ287. Even more striking, the smaller black hole was seen launching a jet of high-energy particles. Because it whirls around its massive partner, the jet twists like a “wagging tail” or a spinning garden hose, changing direction as the black hole speeds along its orbit.