Question

Which of the following paths could not be a real orbit for a planet around the Sun?

Answer 1

Answer: (b) Planet orbit shown as a moderately-flattened ellipse slightly wider than the others with the Sun at precise center of the ellipse. Minor axis is the same as other ellipses.

Explanation:

According to the first Kepler Law of Planetary motion, the orbit of a planet around the Sun, is in the form of an ellipse with the Sun at one of the two foci of that ellipse. This is also valid for any mass orbiting another mass greater than the first one in the space.

In this context, the ellipse is a conic, whose eccentricity  is between 0 and 1. So,  when its value is 0 we are talking about a circular orbit and when it is 1, a parabolic orbit.

That is, the nearer to the value of 1 (without reaching 1) the eccentricity of the orbit is, the more elliptical it will be.

In this sense, the only option that is incorrect is:

(b) Planet orbit shown as a moderately-flattened ellipse slightly wider than the others with the Sun at precise center of the ellipse. Minor axis is the same as other ellipses.

This statement contradicts Kepler's first law, because the Sun is at one of the two foci of that ellipse. The only way in which the Sun can be at the very center of the orbit is when we talk about a circular orbit. Since a circumference is a especial case of an elipse with eccentricity zero and we get only the center instead of the two foci.

Answer 2

Answer:

(b) Planet circle appeared as a decently straightened oval somewhat more extensive than the others with the Sun at exact focal point of the oval. Minor hub is equivalent to different ovals.  

Explanation:

(Kepler's first law discloses to us that the circle of a planet must be an oval with the Sun at one core interest.

Accordingly, the way that shows the Sun in the focal point of the circle, as opposed to at a center, can't be the genuine orbital way of a planet.

[Note that the roundabout way is permitted in light of the fact that a circle is an oval where the two focus are at the center.]