How were black holes first discovered?

Black holes are mysterious. They are so dense that no light can escape them, which makes them super hard to find! So how did we discover the first black hole? We asked NASA engineer Varoujan Gorjian to help us find the answer. Got a mystery you’d love to shed some light on? Send it to us at BrainsOn.org/contact, and we’ll help search the skies for an answer. See omnystudio.com/listener for privacy information.