Black holes are difficult to be noticed and observed, as they are small and emits no light. They can be observed however, by the effects of their enormous gravitational fields on nearby matter. OR with the use of Hubble space telescope, observe radiation signal outside the visible spectrum or radiations of heating particles that are accelerateing towards a massive mass.

In 1974 Stephen Hawkings (above picture) first recognized a property of black holes: black hole is an object in which nothing was supposed to be able to escape. By taking into account quantum mechanics, he was able to show that black holes can radiate energy as particles are created in their vincinity.

When a star collapses and become a black hole, the strength of its gravitational field changes from what it had been before the collapse. But the planets would continue in their orbits as usual and would not be drawn into the black hole. (e.g. our sun become a black hole but our earth will still rotate in its orbit as though nothing happened) Because black holes do not give off any light, the planets would appear to be orbiting around nothing. Although the planets might be orbiting about a star that is too faint to be seen, but there is an equal chance that a black hole could be present.

The Hubble Space Telescope is a cooperative program of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) to operate a long-lived space-based observatory for the international astronomical community. HST is an observatory first dreamt of in the 1940s, designed and built in the 1970s and 80s, and operational only in the 1990s. HST was designed to be a different type of mission for NASA -- a long term space- based observatory. HST is a 2.4 meter reflecting telescope which was deployed in low-Earth orbit by the crew of the space shuttle Discovery on 25 April 1990.