‘Perfect explosion’: merger of neutron stars creates spherical cosmic blast

The explosion, called a kilonova, created a rapidly expanding fireball of luminous matter before collapsing to form a black hole

Astronomers have observed what might be the perfect explosion", a colossal and utterly spherical blast triggered by the merger of two very dense stellar remnants called neutron stars shortly before the combined entity collapsed to form a black hole.

Researchers on Wednesday described for the first time the contours of the type of explosion, called a kilonova, that occurs when neutron stars merge. The rapidly expanding fireball of luminous matter they detailed defied their expectations.