How did Rutherford conclude that the electrons orbited the nucleus in his planetary model? And another way to explain the mass was mostly in nucleus?

Question

In the Geiger-Marsden Experiment, I get how he knew that the nucleus was positively charged, and I'm assuming he knew it was small because the scattering through large angles only happened every 8000 times. However, how did Rutherford know that the electron's orbited? Couldn't he just say the electrons stayed in the empty space.

Also how did he know that most of the mass resided in the nucleus? Is it fair to say since Milikan determined the charge of an electron, and hence using JJ Thomson's q/m ratio, Milikan knew the mass. And hence since the mass of the electron was so small, could Rutherford conclude that most of the mass resided in the nucleus?

Answer 1

Couldn't he just say the electrons stayed in the empty space?
The attractive electrostatic force between the positive nuclei and the negative electrons has to be accounted for. So have the electrons orbiting the nuclei under the effect of the attractive electrostatic force like the planets orbit the Sun because of the attractive gravitational force.

Also how did he know that most of the mass resided in the nucleus?
There was no evidence of the nuclei recoiling when interacting with the incoming alpha particles which indicated that the mass of a nucleus was much larger than that of an alpha particle.