The evidence for the age of the Sphinx is not only that it is aligned with Leo rising for 10,500 BC, but also that the erosion on the body of the Sphinx can only be attributed to rainfall, which did not occur in the region much after 10,500 BC.
Proxima Centauri (from Latin, meaning nearest [star] of Centaurus) is a red dwarf, a small low-mass star, about 4.25 light-years from the Sun in the constellation of Centaurus.
1 The nearest star is some 4.2 light years away, and that distance was known to within an accuracy of better than 0.1 light year.  For a star measured as 20 light years away, the distance estimate is accurate to within a light year or so.