On 4 May, observations by NuSTAR and Swift, the NASA space telescope that spotted the original flare, identified the object conclusively as a magnetar by showing a gradual slowing in its spin rate. This slowing is consistent with the presence of the high magnetic field that enables the star to radiate energy faster than a normal pulsar.
Fourteen magnetars, including this one, have been found in the general region of the Galactic Centre. This high number supports the idea that magnetars tend to form from the death throes of the bright, heavy stars that are common there, says Chryssa Kouveliotou, a magnetar expert at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
The finding also hands astronomers a tool for studying conditions near supermassive black holes. According to Einstein’s general theory of relativity, clocks in high gravitational fields run slow, as a result of the warping of space-time. So if the magnetar is following an elliptical orbit around the black hole, its clock-like spin rate should speed up and slow down as its distance from the black hole varies — an effect that, with luck, could be disentangled from the gradual slow-down caused by the magnetar’s magnetic field.
Frail suggests that the magnetar’s discovery shows that all the excitement over G2 is justified. Astronomers watching G2 say that the cloud itself could deliver plenty more excitement when it finally reaches the Galactic Centre. They are undaunted by the fact that one of the first apparent signs of its arrival turned out to be something completely different. “I wish all of our failed experiments were that good,” says Frail.