Black hole An image of the core of the Whirlpool galaxy M51 taken by the Wide Field Planetary Camera onboard the Hubble Space Telescope. It shows an immense ring of dust and gas which is thought to surround and hide a giant black hole, 1 million times the mass of the Sun, in the center of the galaxy. The ring forms an accretion disc of gas, about 100 light years across, falling toward the black hole. The …showed first 75 words of 1869 total…

…showed last 75 words of 1869 total…revolutionary. It suggested the first link between quantum theory and general relativity and has spawned a host of new ideas which expand the relationship between the two theories. It represents a classical example of a concept which may have little if any direct practical application, but revolutionizes the way in which we view the physical world. Binary System Any system of two stellar-like objects which orbit one another under the influence of their combined gravity.