From: Zardoz ®	04/11/2001 19:34:14
Subject: re: COSMOLOGY FAQ	post id: 484062
How has it been demonstrated that black holes are real? From: Greg L ® Theory indicates in many situations that the formation of a black hole is inevitable, and observations indicate very strongly that black hole's do indeed exist in the universe. From: B.C. ®. Cygnus X-1 is the most likely black hole candidate. First discovered in 1973, the black hole's companion blue supergiant star (HDE 226868) was detected orbiting around an unseen body. In addition, Cygnus X-1 is a strong source of x-rays. Centaurus X-3, identified around the same time, is also a likely black hole candidate. A microquasar known as GRS 1915+105 has been emitting two oppositely directed jets of radio-transmitting gas. GRS 1915+105 is a suspected black hole orbited by an ordinary star. The directed jets appear to be travelling at superluminal speeds due to its direction, right at Earth. Mounting evidence also points to all quasars harboring black holes inside them. Two galaxies, NGC 4258 and M87, are both suspected of harboring black holes. Astronomers were able to come to this conclusion by measuring the velocities of gas and dust around unseen objects. Judging by the data received, only a black hole could produce enough gravity to explain the enormous speed of the gases. Observational Evidence for Black Holes For the first time astronomers have detected material being consumed by the supermassive black hole