October 16, 2017
But Troja and other observers were also puzzled, because they couldn't find any signal in the X-ray and radio regions of the spectrum. These would be expected during the formation of a black hole, which is thought to shoot jets of out of its poles at close to the speed of light. Nine days later, Troja's team was the first to find the X-rays.
Alessandra Corsi, an astronomer at Texas Tech University in Lubbock, and her collaborators kept looking for radio emissions using the Very Large Array in New Mexico. Day after day, the dishes recorded nothing. "It turned out we had to wait 16 very long days in order to see the first radio glow," she says.
The late onset of the radio and X-ray signals, together with the weakness of the initial γ-rays, suggest that the jets were pointed away from the line of sight to Earth. Gamma-ray bursts that happen to be pointed in the right direction can look very bright even from billions of parsecs away.
After a few weeks, most observatories had to stop looking at the object, because that part of the sky had got too close to the Sun. But radio telescopes are still tracking it to this day, Corsi says. More discoveries might yet be made.