THOUGH astronomers talk blithely about black holes, nobody has ever seen one. But now we are getting close. An international team has zoomed in on the object at the centre of our galaxy, and found that it is surrounded by a region of hot gas about 300 million kilometres across, the diameter of the Earth’s orbit. “We are looking at the atmosphere of the black hole,” says Heino Falke of the Westerbork Radio Observatory in the Netherlands.
Most of the radio observations of this region have been scuppered by all the ionised gas between us and the galactic centre, which…
