# Orbiting planets

1. Sep 25, 2008

### Philosophaie

In the case of orbiting planets does the True Anomaly(=0) start at the Argument of Perihelion equal to R at R<1*a and at a minimum? And at 180 + Argument of Perihelion equal to R at R>1*a and at a maximum? Is this true?

2. Nov 19, 2008

### Philosophaie

The True Anomaly (v) is the angle of the Argument of the Perihelion and the position of the earth at a given date. At v=0 the northern hemisphere of earth in at its winter solstice (Jan 3 this year) but the distance from the sun is actually the closest because at v=0 it is at its perihelion. This may sound strange with the Earth being the closest to the sun and the tilted Earth being at the shortest day of the year but think it out and it makes sense. Finally when v=180deg the distance from the sun is maximum and is at its aphelion. The northern hemisphere is at its summer solstice.

3. Nov 20, 2008

### D H

Staff Emeritus
True anomaly is zero at periapsis by definition. What is your real question here?