'Black neutron star' discovery changes astronomy

Scientists have discovered an astronomical object that has never been observed before.
It is more massive than collapsed stars, known as "neutron stars", but has less mass than black holes.
Such "black neutron stars" were not thought possible and will mean ideas for how neutron stars and black holes form will need to be rethought.
The discovery was made by an international team using gravitational wave detectors in the US and Italy.
Charlie Hoy, a PhD student from Cardiff University, UK, involved in the study, said the new discovery would transform our understanding.
"We can't rule out any possibilities," he told BBC News. "We don't know what it is and this is why it is so exciting because it really does change our field."