In our vast universe, the heaviest black holes grew from seeds. Nourished by the gas and dust they consume, or by merging with other dense objects, these seeds grow in size and heft to form the centers of galaxies, such as our own Milky Way. But unlike in the realm of plants, the seeds of giant black holes must have been black holes, too. And no one has ever found these seeds — yet.
One idea is that supermassive black holes — the equivalent of hundreds of thousands to billions of Suns in mass — grew from a population of smaller black holes that has never been seen. This elusive group, the “intermediate-mass black holes,” would weigh in somewhere between 100 and 100,000 Suns. Among the hundreds of black holes found so far, there have been plenty of relatively small ones, but none for sure in the intermediate mass-range “desert.”
In this image, a galaxy called ESO 243-49 is home to an extremely bright object called HLX-1. Circled in this image, HLX-1 is the most likely example of a black hole in the intermediate mass range that scientists have found.
图片提供:NASA; ESA; and S. Farrell, Sydney Institute for Astronomy, University of Sydney