What is the main challenge astronomers face when trying to directly detect black holes?

The main challenge astronomers face when trying to directly detect black holes is that **black holes trap all light**. This characteristic means that they cannot be observed directly since they do not emit light or any form of electromagnetic radiation that can be detected. Instead, astronomers typically infer the presence of black holes through their gravitational effects on nearby objects and the radiation emitted by accreting material as it falls into the black hole.