The conservation of what physical quantity does Kepler's second law refer to ?

Explanation

Kepler.s second law refers to the law of conservation of angular momentum.
According to Kepler.s second law, the area swept out by the line joining the earth and the sun in unit time is a constant.
Area swept out in unit time by the line
`=1/2 r omega xxr=1/2 r^2 omega=k` (constant)
In this case,
r=distance of the earth from the sun
`omega`= angular velocity of the earth around the sun
If the linear speed of the earth is v and its mass is m, the angular momentum of the earth
`=mvxxr=momegar^2=mxx2k`= constant
Thus, the angular momentum is conserved.