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xkcd #2898: Orbital Argument
(imgs.xkcd.com)
Alt text:
"Some people say light is waves, and some say it's particles, so I bet light is some in-between thing that's both wave and particle depending on how you look at it. Am I right?" "YES, BUT YOU SHOULDN'T BE!"
It's called a barycenter, kids, a common center that both objects circle around. That common center happens to be inside the sun, but that's a topic for next week's class in this semester's AP Astrophysics program.
I don't think the barycentre is inside the sun? Wikipedia says on the barycentre article:
The Jupiter-Sun barycentre in outside the sun.
The Earth-Sun barycentre is inside the sun.