Talk:243 Ida

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Should this be called a binary asteroid? The link defines a binary asteroid as one where the two objects orbit their common center of gravity, presumably this designation is the same as that for binary planets, when that center of gravity exists outside the body of the largest object (as is supposedly the case with Pluto and Charon.) If this is the case, then Ida and Dactyl would not be a binary asteroid as Dactyle is very small and the center of gravity in the Ida/Dactyle system is almost certainly within the body of Ida. In fact, references to Ida/Dactyl in other wikipedia articles list it as the first asteroid found to have a moon, rather than a binary asteroid - and in those articles about Ida, the link to asteroids with moons goes to a page describing those rather than to the binary asteroid description page.

I am not changing this because I personally do not know if in fact the center of gravity is within the body of Ida or not, but if someone else does and it indeed is, then this should be changed. Jafafa Hots 04:52, 18 January 2006 (UTC)

It doesn't matter if the satellite is small or comparable to the size of the parent body; all asteroids consisting of two objects are binary asteroids. Similarly, asteroid 87 Sylvia is considered a triple asteroid although its satellites are tiny compared to the parent body.--Jyril 15:42, 18 January 2006 (UTC)