Sometimes they behave like a cloud of gas and then they’ll start behaving again almost like an ordinary star: the so-called “G-objects,” which astronomers describe in an article in the scientific journal Nature, are hard to fit into any single category. Six of these objects have already been identified by researchers. They were all found in the direct vicinity of the center of our Milky Way – orbiting the supermassive black hole, Sagittarius A*. This point of commonality probably also contributes to their strange behavior. G1 to G6 have orbits that lead them around the black hole once every…

Only a billion years after the big bang, there were already galaxies whose centers harbored supermassive black holes several billion times the mass of our Sun. Astronomers know this from observations of far distant quasars and active galaxies. But how were the black holes able to grow so large so quickly? The problem seemed even more complicated, because earlier observations with ALMA, the Atacama Large Millimeter/Submillimeter Array, had shown a lot of dust and gas in these early galaxies, which promoted rapid star formation. However, if a lot of stars were created, there would have been little left over…

One of the distinguishing features of black holes is that they are hard to see. Astronomers looking for them sometimes have luck, but at the cost a star: when a ravenous black hole tears off and devours stellar material from an orbiting star, the resulting accretion disk emits radiation that can be measured. Almost all known black holes have been discovered this way. But it seems logical that those aren’t the only ones out there. Black holes are formed when heavy stars die. And many of these giant stars die alone, without a companion that a resulting black hole…