bull rider, cowboy sun

seeing the picture in the end of this page
[link to astronomy.stackexchange.com (secure)]

I started to wonder why such a so regular pattern for our orbit move

I understand small "bumps" in an orbit (say, ours around sol) due to gravity from closer or not so but larger bodies (also all in their varied moves) but would not expect an "up down" pattern so large, and with so highly fixed, predictable period around center of mass of our galaxy