An international team of astronomers, led by researchers from the Max Planck Institute for Radio Astronomy, have used the MeerKAT radio telescope to discover an intriguing object of an unknown nature in the globular cluster NGC 1851. The massive object is heavier than the heaviest neutron stars known and yet simultaneously lighter than the lightest black holes known and is in orbit around a rapidly spinning millisecond pulsar. This could be the first discovery of the much-coveted radio pulsar – black hole binary; a stellar pairing that would allow new tests of Einstein’s general relativity. See here the original paper A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes (E. Barr et al., Science, January 19, 2024, Vol 383, Issue 6680, pp. 275-279, DOI: 10.1126/science.adg3005).
Read here the MPIfR press release.
Image: © MPIfR; Daniëlle Futselaar (artsource.nl); An artist’s impression of the system assuming that the massive companion star is a black hole. The brightest background star is its orbital companion, the radio pulsar PSR J0514-4002E. The two stars are separated by 8 million km and circle each other every 7 days.