Halo-verse Planetary Scale
Article by Stephen Loftus [SoundEffect]
On October 16, 2005, Stephen put together an image showing the relative sizes of known planets in the Halo-verse; both the Halo system and our own. (He wishes we had sizes for Reach, Sigma Octanus, etc., but we don't.)
Update, 10 December 2009: Stephen added the Ark (Installation 00) to the mix - size was calculated using the requirement that the Halo be able to fit in the Foundry at the Ark's center.
Update, 28 July 2011: Stephen completely reworked this guide to accommodate some new figures and names we now canonically known.
You can see the full image he created (3358x2042, 328K) in its own window by following this link. If you'd like to navigate around the image, you can click within the various red boxes above - you'll zoom in on the section in question.
Additionally, he's actually figured out the true distances to the planets/moon from Each Halo ring using some math he hadn't used since university astronomy class and some age-old screenshots. You can see this image below (click to embiggen - 2615x1524, 163k). From Stephen:
I also had some assistance from a smart (and cute) mathematician at my workplace to figure out the best formula to use to derive the distances. Her calculation was superior to the one I'd figured out. Thanks for the help, Mehrangiz!