A single "runaway" star in a distant star cluster could explain how a massive supernova avoided collapsing into a black hole, leaving behind a remnant object instead.
The find explains the presence of a magnetar — a bizarre object that is not only highly dense but also extremely magnetic — in the star cluster Westerlund 1, about 16,000 light-years from Earth. Magnetars are a rare type of neutron star that is left behind after a supernova explosion. They are also known by their "starquakes" that send gamma ray radiation into the cosmos. You can watch a video about the magnetar on Space.com.
Magnetar CXOU J164710.2-455216 has been known for some time, but what puzzled astronomers was how it formed from an exploding star that was likely 40 times as massive as the sun. At that mass, nothing should have been left behind from the implosion besides a black hole.