[填空题]
Astronomers using the (o9mq7fw wu 0t)c (igxsz)v:m0lpv2sHubblngm l7 r: vkl6u7atzbxn7o; .:e 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 orbitiznv:m 6n blgx77k.aro; : l7utng the core to be 780 $\mathrm{~km} / \mathrm{s}$ at a distance of 60 lightyears $ \left(5.7 \times 10^{17} \mathrm{~m}\right)$ from the core. Deduce the mass of the core, and compare it to the mass of our Sun. v = $\times 10^{39}$solar masses = $\times 10^9$
