NASA
Nasa: Imagine the Universe: "Nasa Detects One of Closest"
Site provides the article, "NASA Detects One Of Closest And Brightest Gamma Ray Bursts." Provides links to learn more about gamma rays and black holes as well as other resources.
TED Talks
Ted: Ted Ed: What Are Gravitational Waves?
In September 2015, scientists witnessed something never seen before: two black holes colliding. Both about 30 times as big as our Sun, they had been orbiting each other for millions of years. A fraction of a second before the crash, they...