Comment by thayne

What you're describing is a coincidence.

What I'm describing is an artifact in your data that is caused by the motion of the earth.

To give a more concrete example, suppose you measuring the brightness of a trans-neptunian object, and observe that the brightness changes slightly with a period of about 1 year. You might think it has a non-uniform albedo, and a rotational period of one year, when in reality, it is just brighter when the earth is closer to it.