Astronomers have spotted a mysterious cosmic object that could be the lightest black hole or the heaviest neutron star ever discovered — or something completely new to science.
The unknown object, discovered 40,000 light-years away inside a dense globule of stars named NGC 1851, was detected through the rapid flashes of its orbiting companion — a rotating neutron star known as a pulsar that sweeps out a beam of light once every 6 milliseconds.
