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Astronomers using the Hubble Space Telescope deduced the presence of an extremely massive core in the distant galaxy M87, so dense that it could be a black hole (from which no light escapes). They did this by measuring the speed of gas clouds orbiting the core to be 780km/s at a distance of 60 light-years (5.7 × 1017 m) from the core. Deduce the mass of the core, and compare it to the mass of our Sun.
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