I'm just wanting to check my understanding of the basic statements in Wikipedia (paraphrased, rather than directly quoted).
- Venus has an orbit, proceeding in the usual direction for planets in our Solar system (a counter-clockwise direction, if viewed from a point above the ecliptic plane, that would look down on Earth's North pole), with an orbital period of 224 Earth-days.
- Venus has a north pole that is nearly straight up from the plane of its orbit (inclined only 2.6° from it) and it rotates about this pole in the opposite direction of other planets, rotating clockwise, with a sidereal day of 243 Earth-days.
- Venus is undergoing a process of tidal locking with the Sun, so its rotation is being slowed, until eventually it will be tidally locked.
If we don't assume any change in Venus' orbit, then, when it becomes tidally locked, it will be rotating counter-clockwise in the above perspective with a sidereal day of 224 Earth-days. So, part-way through this process, Venus will experience a total stop of its rotation from the perspective of the fixed stars, with a sidereal day that is infinite (until it starts slowly rotating clockwise from this viewpoint).
If this is correct, then it would at that point be a great time to be an astronomer on Venus (in some ways), except for the unfortunate irony that the cloud-cover spoils any view of anything. Those of us who complain about cloud-cover spoiling everything neat that comes up in Earth's skies (I am guilty) can then, by comparison, count our lucky stars (literally).
Incidentally, if a planet's orbit is eccentric, then by Kepler's laws, I doubt it can ever become truly tidally locked (I mean I think the Sun would not be totally fixed in the planet's sky). It might be fun to work out how such a body would actually behave in its view of the Sun, and what tidal dynamics might remain, with what effect over long periods of time. Venus happens to have very little eccentricity in its orbit, so I assume this will not be an interesting case. It is interesting in the case of Mercury, where the orbit is eccentric and the effect of orbital speed-up near perihelion messes with the solar position quite visibly. But I think Mercury is far more complicated than my simple mental model, so there's probably more going on than I realize.
I also note that Mercury has almost zero axial tilt. Is this guaranteed for a tidally-locked body? I mean it seems as though the tidal locking process is going to result in that. Is that correct?