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What are black holes? Black holes are concentrations of mass that are so great that not even light can escape. They are often the result of stars that have run out of nuclear fuel but have collected more mass than the internal nuclear reactions can keep from collapsing on itself.

The actual term "black hole" was first coined by Physicist John Wheeler (1911-) around 1967. Previous to this they were sometimes refered to as "black stars".

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Why are black holes important? Having an understanding of blackholes helps us understand some of the most fundamental forces in the universe. Black holes can be important from a number of perspectives. From a cultural perspective black holes have inspired science fiction movie themes frequently. For example the movie Black hole (1979) and more recently a movie called Event Horizon (1997). From a technological perspective black holes have been a motivation to develop new astronomical techniques and tools. For example investigation of gravitational waves , something that black holes may produce, can be detected by the development of very senstive instruments.

Are black holes totally black? One of the weird things about black holes is that they may not be entirely black. According to quantum theory (a theory in which atomic particles can be in several places at once) suggests that blackholes may actually 'evaporate' after a little while. Black holes may be an important source of gravitational waves. For example if two black holes started to orbit around each other it would likely cause ripples in space itself. Black holes may be a cause of gravity waves Image: Caltech, Corey Gray Black holes may also be important for helping other stars to form. For example the gravity of black holes ( like other large stellar objects) may promote nebulae to form stars. Stars forming around a supermassive black hole at the centre of our galaxy. Image: NASA

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News about black holes Stars are reported in the news almost daily, astronomers often report on new star discoveries, particularly stars that are unusually large, small or Try a search of Google news for black holes for some of the latest headlines around the world.

Some reliable resources about stars Stars - BBC Science About stars - hubblesite.org   It is sometimes useful to visit local astronomical observatories or universities that study stars for the latest research areas. ANU research school of astronomy and astrophysics

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How are black holes studied? Black holes are studied in two main ways. One is through observing (with various types of telescopes) areas of space which have stars that are close to black holes. The other way black holes are studied is through mathematical theory and computer simulations. An important mathematical tool for studying black holes is Einstein's General Theory of relativity.   How do black holes work? how do they form? How can a star turn into a black hole? A star which has a very large amount of mass will go through a series of nuclear reactions that converts element into element. Some times the reaction is so violent it is called a super nova. But even then then a small amount of the star is left over called a neutron star, if there is still too much mass then the star will just collapse in on itself and just go black. reference: Cambrindge Univeristy, Black holes

How are black holes classified or categorised? It turns out that black holes come in various different types. Some a super massive, like the one that is thought to be at the centre of Milky way galaxy. There are generally considered 3 types of black holes. stellar mass balck holes supermassive black holes miniture black holes reference: amazing-space Space telescope science instute   Here is an what black hole of 10 solar masses would look like if you saw it from 600km away. It shows how the star light is distorted when looking at it towards the milky way. image:Wikipedia

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What is the history of black holes? The natural history of black holes It is possible that the early few seconds of the universe had spots that had very high mass and minutre black holes formed. But this is mostly theoretical. But it is more likely that stellar black holes later in the universe were the dominating type. These stellar black holes are the ones that astronomers can find evidence for using telescopes.

The cultural history of Black holes Who were the the key people who even thought of the concept of a black hole? Interestingly, it was an English geologist John Michell (1724- 1793) who considered the concept of a mass so large that light could not escape. French mathematician Pierre-Simon Laplace suggested the same concept in 1796. But it was Albert Einstein in 1915 who created the mathematical thinking of the general theory of relativity which describes black holes best. His theories really deal with what happens as things approach the event horizon. More recently Stephen Hawking in 1971 has been noted for his calculations of evaporating black holes and so called Hawking Radiation.

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The future of black holes Black holes are one of the most unusual objects in the universe that we have good evidence for. But the exact workings are still far from clear. There is some suggestion that black holes don't actually exist in the way we think today. One of the contentious ( argued) point is what quantum mechanical theory may suggest about what might be near the event horizon.

There are some suggestions that black holes may be balls of particles that never actually collapse into a point. Such issues are rather theoretical and don't seem to provide much difference in the things that astronomers can actually observe. Perhaps new physics such as M-THeory and superstring theory will provide a more useful theoretical framework in the future. reference: Wikipedia- Gravastar

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