The researchers analyzed data from the Low Frequency Array (LOFAR) radio telescope, a vast network of over 100,000 small antennas spanning eight European countries.

While studying a galaxy cluster named SpARCS1049, the researchers detected a faint, widespread radio signal. They found that it did not emanate from individual galaxies, but from a vast region of space filled with high-energy particles and magnetic fields.

Stretching over a million light-years, this diffuse glow is a telltale sign of a mini-halo, a structure astronomers have only been able to observe in the nearby universe up until now.