Years after we detected two neutron stars crashing into each other, we’re still picking up X-rays. We don’t know why
After a thousand days of observations, the continuing X-ray radiation from two neutron stars smashing into one another has left astronomers puzzled.
The collision, code-named GW170817, was picked up by our planet’s LIGO and Virgo gravitational wave detectors in mid-2017. The incredible crash, some 130 million light-years away, spilled a heady mix of electromagnetic signals into space as well as the gravitational wave we detected here on Earth.
One remarkable feature of the merger was its kilonova, which immediately followed an initial gamma-ray burst. Light from this kilonova faded about three weeks after GW170817 was observed, as expected. Curiously, though, X-rays were picked up nine days after the merger’s gravitational wave was detected, and they continue to linger well past what’s typically considered normal. The X-ray afterglow is still visible three years after the detection of GW170817.