[填空题]
Astronomers using the Hubble Space Te ymz*m. 4 i.v)yofrkq;lescope deduced th.45 *h 40yiqaqxd fbxwe 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 05xiqf4d y .aqbwx*4 h 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 = $\times 10^9$
