[填空题]
Two equal-mass stars mb5 g1 b4hs;ffxdy dkem31-i6paintain astbg6*)qm6b xn.tl1 g constant distance apart of 8.0 $\times 10^{10} \mathrm{~m} $ and rotate about a point midway between them at a rate of one revolution every 12.6 yr . (a) Why don't the two stars crash into one another due to the gravitational force between them?
(b) What must be the mass of each star? $\times 10^{26}$
