How is velocity calculated at perihelion?

1 Answer
Mar 10, 2016

4-significant digits (sd) approximation: 30.79 km/s


Easy formula for velocity at perihelion and aphelion:

If V is the speed at the distance equal to semi-major axis a ( at an end of the minor axis) of the orbit, Vp and Va are speeds at perihelion and aphelion and e is the orbit eccentricity.
#Vp = V((1+e)/(1-e)) and Va = V((1-e)/(1+e))#
V - 29.774 km/s, nearly. e = 0.01671, nearly.

The directions of motion at perihelion and aphelion are perpendicular to the radius from the Sun to the Earth.