The team used China's Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to find stars orbiting objects that are seemingly invisible -- a technique that had been proposed back in 1783, but hadn't really been possible until recently. They then used both the US' Keck I telescope and Spain's Gran Telescopio Canarias to determine the properties of both the star (in a tight, 79-day orbit) and its companion black hole. Previous detection methods required looking for holes eating gas from a star, making sightings relatively rare.
Expectation-shattering discoveries aren't new, even in recent memory. Astronomers recording gravitational waves have found that the colliding black holes producing the waves are far larger than usual. However, this could force a significant rethink of how stellar black holes are born. That, consequently, could change how humanity understands galactic activity on a broader level.