It is shown that the SMC lies close to the spin plane of the LMC. There is a sufficient angle in the sky between the Magellanic Clouds that even if the LMC were moving purely transversely to the line of sight with the SMC moving with it, about one quarter of that transverse motion would be seen as a radial velocity of the SMC. Supplementing this idea with other arguments we deduce that the Magellanic stream trails ‘behind’ the Magellanic Clouds. Allowing for a possible halo to the Galaxy we compute models that last for 1010 yr and fit the observed velocities of the Magellanic stream. These give a large orbit for the Magellanic Clouds running from 50–200 kpc from the Galaxy. The stream was detached not during the current close passage, but at the last one. Differences of period have drawn out the stream during approach to the current passage which may have just severed the binary motion of the Magellanic Clouds. The ‘circular’ velocity required to produce a halo sufficiently massive to cause the Magellanic stream is Vc = 244 ± 20 km s−1 which must be maintained to distances of over 70 kpc from the Galactic Centre.
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Lin et al. (1982) studied this question.