Johannes Kepler's work in astronomy mainly dealt with what aspect of orbiting objects?

Question

a
The masses of the objects in orbit
b
Their orbiting motion and the shape of the orbital paths
c
Their orbit sizes and the contraction and expansion of those orbits
d
The orbital speeds and how the masses affect their speeds

Answer 1

Johannes Kepler's work in astronomy mainly dealt with:

b. Their orbiting motion and the shape of the orbital paths.

Kepler is best known for his three laws of planetary motion, which describe how planets move in elliptical orbits around the sun, the relationship between the time a planet takes to orbit the sun and its distance from the sun, and the rate at which planets sweep out areas in their orbits.