Free Astronomy Magazine May-June 2020

31 MAY-JUNE 2020 SPACE CHRONICLES sources to find strong evidence for this one IMBH candidate. Once found, the X- ray glow from the shredded star al- lowed astronomers to estimate the black hole’s mass. Confirming one IMBH opens the door to the possibility that many more lurk undetected in the dark, waiting to be given away by a star passing too close. Lin plans to continue this meticulous detec- tive work, using the methods his team has proved successful. “Studying the origin and evolution of the intermediate mass black holes will finally give an answer as to how the supermas- sive black holes that we find in the centres of massive galaxies came to exist,” added Webb. Black holes are one of the most extreme en- vironments humans are aware of, and so they are a testing ground for the laws of physics and our un- derstanding of how the Universe works. Does a supermassive black hole grow from an IMBH? How do IMBHs themselves form? Are dense star clusters their favoured home? With a confident conclusion to one mystery, Lin and other black hole astronomers find they have many more exciting ques- tions to pursue. T his Hubble Space Telescope image identified the location of an intermediate-mass black hole (IMBH), weighing over 50,000 times the mass of our Sun (making it much smaller than the su- permassive black holes found in the centres of galaxies). The location of the black hole, named 3XMM J215022.4− 055108, is indicated by the white circle. This elusive type of black hole was first identified via a telltale burst of X-rays emitted by hot gas from a star as it was captured and de- stroyed by the black hole. Hubble was needed to pinpoint the black hole’s location in visible light. Hubble’s deep, high-resolution imaging shows that the black hole resides inside a dense cluster of stars that is far beyond our Milky Way galaxy. The star cluster is in the vicinity of the galaxy at the centre of the image. Much smaller images of distant background galaxies appear sprinkled around the image, including a face-on spiral just above the central foreground galaxy. This photo was taken with Hubble’s Advanced Camera for Surveys. [NASA, ESA, and D. Lin (University of New Hampshire)] is strong enough for them to be con- stantly drawing in stars and other cosmic material and producing the tell-tale X-ray glow. Astronomers therefore have to catch an IMBH red-handed in the relatively rare act of gobbling up a star. Lin and his colleagues combed through the XMM-Newton data archive, search- ing hundreds of thousands of !