Mysterious radio signal coming from the heart of an ancient star cluster in the Milky Way. It could have been emitted by a pulsar, a rapidly rotating neutron star, or by a medium-sized black hole.
The site contains more than a million stars and is the second most luminous place on the planet. Researchers detected the mysterious signal while examining the globular cluster called 47 Tucanae with the Australia Telescope Compact Array, a radio telescope operated by the Australian Government Agency for Scientific Research.