Please don't confuse astrology and astronomy! They may once have been the same, but they're certainly not now.
Astrology is the study of the movement of celestial bodies in the belief that they somehow influence Earthly affairs. It's utter bunkum, and there's considerable weight of scientific evidence to explain exactly why (but briefly, if the planets and their alignments did really affect some sort of force upon the Earth, it would have to be either gravitational or electromagnetic, and be measurable on large groups of people over a period of time. It isn't, because it doesn't exist. See here for more:
http://www.badastronomy.com/bad/misc/astrology .html)
Astrology, by contrast, is "the scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena." A very different kettle of vomit altogether.