Controlling the cosmic energy budget: Stars and supermassive black holes in galaxies

Galaxies are not simply conglomerations of stars, gas and dust. They are the building blocks of the Universe, the ultimate energy factories and at least one of them is home to intelligent life. In fact, besides the Big Bang, the origin of most electromagnetic radiation in the Universe can be traced back to galaxies. Nonetheless, the existence of supermassive black holes in galaxy centres, although now well-established, is still puzzling scientists. How did these mysterious objects come to be? When did they first form? Is there one in the centre of every galaxy? More puzzling yet, is the idea that they can regulate the formation of stars in the galaxies in which they reside.