Some stars just get unlucky. There are billions of stars within a typical galaxy. Yet once every 100,000 years or so, one of those stars will wander too close to the supermassive black hole lurking at the galaxy’s centre and be torn apart. These cosmic behemoths weigh in at millions to billions of times the mass of our Sun, and their immense gravitational force can destroy an unlucky star.
The stellar debris spirals in towards the black hole, which feeds on the remains. However, black holes are messy eaters. In a small fraction of cases, this stellar destruction can power an energetic jet of material that travels outwards at almost the speed of light. If that jet is pointed directly towards us its brightness will be boosted, in much the same way that a police siren seems louder when the car is travelling towards us.
