Astronomy Cast - Ep. 213: Supermassive Black Hole

On this episode of Astronomy Cast, the hosts discussed a relatively recent development in astronomy, Supermassive black holes. There is now thought to be one at the center of every galaxy in the universe, including our own Milky Way. Their discovery is a result of observing the orbital speeds of stars close to the center of the galaxy. They were observed to be moving at phenomenal speeds, and the calculated mass of the object they are orbiting was found to be millions of times more massive than the sun. Exactly how they came to be so much more massive than black holes made by collapsing stars is still poorly understood. They could not have been formed in the big bang, as all models predict an even distribution of mass in the early universe. Some other theories suggest that they could have been formed over time by simply accruing a lot of material. However, this process would take a very long time (longer than the time a stellar black hole would have had to grow to the size of a supermassive one) due to the fact that not all matter that approaches a black hole falls in. A lot of the matter is actually jettisoned through jets near the poles of the black hole. The matter is jettisoned with very high energy at relativistic speeds at both poles of the black hole. Strangely, when these jets are faced towards us the physics involved with them causes the matter to appear to be moving faster than light speed. The only thing stopping them from actually achieving such speeds is the relativistic effect of the black hole itself, which actually slows down time around it.