Neutron stars, the remnants of medium-size stars after a supernova explosion, are expected to be in a state analogous to superconductivity. Larger stars were thought to collapse into “black holes”, but Chapline and Laughlin’s theory, based on some calculations with Emil Mottola, Pawel Mazur and others, is that they would instead develop this quantum critical state – to outside observers it may still look like a black hole, but it’s very different on the inside.
The quantum critical state only exists in a thin shell, roughly where a black hole’s event horizon would be. As the stars mass collapses through the quantum critical shell, it is converted to energy; inside the shell is essentially a vacuum filled with this “dark energy”, similar to the dark energy now observed to be filling our universe.
In fact, the universe itself may be just one very large dark energy star; the unobserved “dark matter” in our universe may also be explained by large numbers of small dark energy stars formed when the universe was young.
Black holes and dark energy stars may look the same, but they are expected to behave differently with regard to matter going through the shell or event horizon – a dark energy star would bounce a lot of energy back out of the shell with specific signatures – signatures that may have already been seen in the form of positrons and gamma rays from known celestial objects.
Mottola was involved in an earlier similar alternative for black holes, the gravastar – this new dark energy star seems to be an evolved form of that earlier idea.