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Ignoring any current beliefs, is it possible that the planets could have been captured by the Sun's gravitational force after drifting through space while retaining their axis of spin and speed?

Notably, Venus uniquely has retrograde rotation; how would this have come about based on current theories?

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I'll address the second question first, Venus uniquely has retrograde rotation; how would this have come about based on current theories? The answer is that there are a number of hypotheses related to Venus's rotation. See the related question What is the current accepted theory as to why Venus has a slow retrograde rotation?. None of them involve capture of a rogue planet. Note that this also applies to Uranus; it too has an odd orientation.

So why not? Note that I am now addressing your first question, is it possible that the planets could have been captured by the Sun's gravitational force after drifting through space while retaining their axis of spin and speed?

The answer is simple. Capture is extremely unlikely (and that's putting it mildly), and it is not needed to explain the odd orientations of Venus and Uranus.

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  • $\begingroup$ Thank you.I have no argument but how would the change be effected.respectfully.Colin $\endgroup$ – Colin Shorey Jan 16 '15 at 19:24
  • $\begingroup$ What change? There is no reason to invoke an extremely unlikely event to explain a very likely event. $\endgroup$ – David Hammen Jan 17 '15 at 3:47
  • $\begingroup$ You feel capture most unlikely? Maybe so but Pluto was considered this way for many years because its orbit comes within that of Uranus.Current thinking is that it is no longer a planet.Cheers,Colin $\endgroup$ – Colin Shorey Jan 17 '15 at 4:26
  • $\begingroup$ @ColinShorey - That,sir, is a non sequitur. $\endgroup$ – David Hammen Jan 17 '15 at 4:44
  • $\begingroup$ I wouldn't say capture is "very unlikely". Capture of Oort cloud objects is thought to be fairly common. en.wikipedia.org/wiki/Oort_cloud#Origin but for a planet to be captured it would need to go from one very distant orbit to another (and it would need to meet the definition of a planet). We don't know enough about very distant orbiting objects to say how often planets get captured. $\endgroup$ – userLTK Oct 14 '17 at 17:01

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