In 2017, detectors picked up a tremor in space — gravitational waves from the merger of two neutron stars. At the same moment, telescopes saw a flash. For the first time, one event spoke in two languages at once: light and gravity. But the longer astronomers watched the fading glow, the stranger its behavior became.
Usually, such a collision produces a narrow jet — a beam of particles traveling at nearly the speed of light. If the jet is pointed away from us, its light should fade quickly as it expands. Here, things were different: the brightness declined very gradually. As if something kept illuminating the expanding cloud from within. This didn't fit the picture of a straight beam.
The authors of the study proposed that the jet wasn't stationary. It wobbled, like a garden hose under high pressure, tracing a glowing ring across the sky. Over time, we see a longer arc of this ring — which is why the light fades so slowly. Computer simulations showed that such a 'wobbling' jet explains the observations 4.8 times better than a rigid narrow beam.
This isn't just solving one event. Slow fading has been seen in other gamma-ray bursts as well. If wobbling jets are common, our understanding of the most powerful explosions in the Universe is about to become much more dynamic.
If such a wobbling jet shone in visible light, a distant observer would see not a point but a gradually brightening and dimming ring, a cosmic 'donut' the size of the full Moon.
In Arthur C. Clarke's novel '2010: Odyssey Two', a mysterious ring on a moon of Jupiter turns out to be a gateway to other worlds — here, the ring is drawn by the physics of the explosion itself.