Is dark matter made of axions? Black holes may reveal the answer
(PHYSorg.com Space & Earth)

What is dark matter made of? It`s one of the most perplexing questions of modern astronomy. We know that dark matter is out there, since we can see its obvious gravitational influence on everything from galaxies to the evolution of the entire universe, but we don`t know what it is. Our best guess is that it`s some sort of weird new particle that doesn`t like to talk to normal matter very often (otherwise, we would have seen it by now). One possibility is that it`s an exotic hypothetical kind of particle known as an axion, and a team of astronomers are using none other than black holes to try to get a glimpse into this strange new cosmic critter.