We can detect the matter and light emitted around these black holes, but within the event horizon, nothing escapes. The Event Horizon Telescope attempted to image the event horizons of both of these, with mixed results. We can learn, as we gather more black holes, whether the masses we infer for black holes from either their gravitational effects or their X-ray emissions, are universally biased or not. We now live in a world where we can image the event horizons of black holes directly. Black holes are real, and they're spectacular.

Source: Forbes April 10, 2019 13:18 UTC