Question

How are the perihelion and aphelion of a planet determined?

Answer 1

From semi-major axis a and eccentricity e, the perihelion is a(1 `-`e) and aphelion is a(1 + e).

Explanation:

For the Earth, a = 149.6 million km and e = 0.01671. So, perihelion = 147.1 million km and aphelion = 152.1 million km.