Talk:Orbital period

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Whispers from the land of ignorants ...

This is a great article (Orbital Period page). I don't quite understand one section, however. The point under the 2-bodies-orbiting section: "... the sum of the semi-major axes of the ellipses in which the centers of the bodies move, or equivalently, the semi-major axis of the ellipse in which one body moves, in the frame of reference with the other body at the origin (which is equal to their constant separation for circular orbits) ..."

To use this in the calculation for determining the orbital period -- would I just sum the semi-major axes for both ellipses? E.g. two stars orbiting each other: "Star A" has a semi-major axis of 100 AU, and a mass of 1.5 Solar Masses. "Star B" has a semi-major axis of 300 AU, and a mass of 0.25 Solar Masses. Would I use 400 AU in the formula?

Thanks, Tesseract501@aol.com (August 27, 2005)

Mass and semi-major axis are inversely proportional, so the example does not seem possible, but yes, we just add the semi-major axes.--Patrick 00:03, 28 August 2005 (UTC)

You'd use the total distance, 100+300 AU, and the total mass, 1.50+0.25 M_Sun.

Urhixidur 15:35, 14 December 2005 (UTC)

Letter P and letter T are both used in this article to signify orbital period. Which one should be preferred ? Bo Jacoby 10:32, 14 December 2005 (UTC)

I would say T, like Frequency uses.--Patrick 14:05, 14 December 2005 (UTC)