[填空题]
Astronomers using the Hubb:1 i.hl9dn /mzno6xp7v vdv.a-t/ abrlesh w5aq*fe3 x 1g:y,1 slloob/ Space Telescope deduced the presence of an extremely massive core in the distant galaxy M87, so dense that itx3es q5b/ gfos*al1o:l h,w1y 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 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 = $\times 10^9$
