[填空题]
Astronomers have recently measure /0k zq:1kt2ra u)wpzad the rotation of gas pthuxjtle8;f 8 -+ 0dgaround what might be a supermassive black hole of about 2 billion solar masses at the center of a galaxy. If the radius from the galactic center to the gas cloud+ h8e-dftj gl8uxt0p;s is 60 light-years, what Doppler shift $\Delta\lambda/\lambda_0$ do you estimate they saw? z$\approx $ $ \times 10^{-3}$
