Asteroid Tomorow? 1-12-10

I was listening to Brian Williams on NBC News on TV tonight and he seemed to be talking about an asteroid that one might see during the day as a shining light that would pass about 30,000 miles from Earth. I just looked up Earth's average distance from the moon which appears to be 384,403 km or 238,857 miles approximately. Originally I think got the moons diameter confused with the distance to the moon but this appears to be the correct distance. I guess my question would be: "Have all the variables of gravity pulls of all objects in the solar system been properly calibrated as to their effect on this asteroid? Also, since we are likely in a 26,000 year cycle with the Galaxy has the extra pull of the galaxy during this time been calculated properly as well? It seems to me that calculating an object traveling a path different than a planet or star which would tend to be more regular might be difficult and to be sure all the long distance gravitic effects might be difficult to calibrate effectively especially if an object were of an irregular shape and was tumbling through space.

It is my belief that most but not all asteroids (in the solar system) are pieces of moons and planets of our solar system that have been dislodged through previous collisions with planets and moons. Also, I'm not sure if it has been determined definitively whether or not this particular asteroid is from this solar system or whether it is a runaway from another star system. Also, hopefully, since the trajectory of this object assumably has been well calculated, hopefully, they are right about the trajectory missing earth otherwise it would be like when the dinosaurs ended only we would be the dinosaurs this time.