Space

Those Gravitational Wave Black Holes May Have Merged Inside A Massive Star

February 19, 2016 | by Jonathan O'Callaghan

Photo credit: The black holes may have originated in a "dumbbell" shape like this. NASA

It’s barely been a week since we discovered gravitational waves for the first time from merging black holes, but the follow-up stories are already coming thick and fast. We’ve already heard of new missions taking place and the hunt for visible light associated with the merger event, but now an intriguing piece of research has surfaced related to the source of the merger.

As reported by New Scientist, following the detection of gravitational waves by LIGO, scientists using NASA’s Fermi gamma-ray space telescope detected a flash of gamma rays 0.4 seconds after the signal from the merger was spotted. The chance of the two signals being a coincidence and unrelated was calculated at 0.0022 percent.

What does this mean? Well, according to astronomer Avi Loeb from Harvard University, the merger itself couldn’t account for the flash of gamma rays. Instead, he is proposing that the two black holes were actually inside a massive star, several hundred times more massive than the Sun. Following the merger, the star collapsed, and produced this intense beam of gamma rays.

We know that stars can produce single black holes when they collapse, but Loeb says that a rapidly rotating star could have shaped the core into a “dumbbell,” which broke into two cores that individually collapsed to form the two black holes.

“I show that the two signals might be related if the black hole binary detected by LIGO originated from two clumps in a dumbbell configuration that formed when the core of a rapidly rotating massive star collapsed,” he wrote in his paper, available on Arxiv.

This is very much only a theory at the moment. Indeed, another gamma-ray spacecraft, the European INTEGRAL, wasn’t able to reproduce the detection by Fermi, suggesting that it might not be a real signal.

But if it is real, it means the merging black holes must have been surrounded by a lot of material in order to produce this flash of gamma rays. And it seems placing the two black holes inside a massive star might be one way to explain how that was possible.

Whatever the case, it’s rather amazing how much research is being done off the back of this one detection that lasted just 7 milliseconds. Think of the science that will be possible when more detections are made.

[H/T: New Scientist]

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