It is probably a star-gas-planet similar to the brightness of Jupiter and the movement of Venus. If it is not, it might be related to the big dipper/little dipper opposition interactions. I do admit Venus can also do that sometimes and so can Jupiter. The only flaw is Venus and Jupiter both does not stay there for a steady and complete predictions. That's why scientists perfer to graph the motion of Jupiter and Venus than actually predicting them. Sirius is the brightest visible star of the entire galaxy(ies) set(s) and is still visible in day (as long as someone use the telescope). Sirius star is not hidden unless something covers it. Even so, one can still sense Sirius star's light, magnetivity, and gravitational forces. There is really a very small chance that the Sirius star and star set(s) will leave the universe.
http://star-www.st-and.ac.uk/~fv/sky/feb11.html
http://www.arksky.org/index.php?pid=105

For the flipping of the core, I think it is common to change the navigation units. After all, if the atmosphere of the earth is completely broken, navigation itself will require a solar shield or planetary shield. Within the shield, there will be a navigation system that provide the shield and tell the difference of the world. Of course, this is already possible with some satellites NASA send out. The hubble space satellite is trying to reach the nineth planetoid, Pluto. At least, that is their goal for 2011 to about year similar to 3000