Black Holes Or Dark Matter?

What exactly are the supermassive objects at the centre of galaxies? Recent theories have maintained that they are black holes, devouring matter from the space around them and churning out X-rays. But a physicist in Texas thinks that they may be something to do with axions, a type of hypothetical particle that is one of the candidates for the origin of ‘dark matter’. It all boils down to the fact that we don’t really understand how gravity works at large scales evenm nearly as well as the scientists would like to – not yet, at least.