An 'impossible' black hole merger may finally be solved thanks to Einstein's relativity — but it raises an even bigger mystery

Scientists suggest the GW231123 signal from a black hole merger with masses 100 and 130 solar masses was amplified by gravitational lensing. Then the final black hole's real mass is about 140, not 230 solar masses, and it does not fall into the 'mass gap'. There is no direct evidence of lensing; the theory is purely theoretical.

• Signal GW231123 detected by LIGO on November 23, 2023, 2 billion light-years from Earth
• Initial black holes weighed 100 and 130 solar masses — 'forbidden' sizes
• Lensing could be caused by an object of 190–850 solar masses
• With lensing, final mass is about 140, not 230 solar masses