'Messy eaters'

(Article Precis, 26/Sep/1998, Issue 2153, p14)
"Some black holes may push away more matter than they devour"
Charles Seife reports on new ideas into why some black holes aren't radiating as much energy as one might expect.

Any gaseous material near a black hole falls in, generating considerable heat as its gravitational energy is converted into X-rays, making the black hole very bright.

At least, that has been the conventional theory. However, some black holes are not as bright as one would expect if all the gas around the black hole was indeed being devoured in this way; the black hole which astronomers suspect may be at the centre of our own galaxy is one such example.

One possible explanation is that not all black holes are capable of converting all of the gas that surrounds them. A new mathematical model developed by astrophysicists in the USA offers an alternative view. The model suggests that a black hole which is surrounded by a smaller quantity of gas experiences a distortion of its magnetic field as the gas molecules move in their orbits, resulting in a loss of kinetic energy in the molecules as they dive into the black hole. This distortion may cause proportionally greater amounts of gas further out to be blasted away, resulting in only a moderate amount of gas falling into the black hole.

However, though this is a distinctly possible theory, there is still a great deal that astronomers do not understand about black holes. More works needs to be done before concrete answers may be found.

Note: In order to comply with copyright law, I have ommited some details from the original article. Thus, for a complete insight into the topic covered here, please either consult your local library for the issue concerned, purchase the relevant issue from your local newsagent, or back-order it from the publishers.

Precised by Ian Mapleson, 04/Oct/1998.