The person who has been looking, through camera images taken at the San Fernando Observatory in California, can't believe his eyes. Examining images taken between May 1986 and August 1997, Chapman plotted the sun's average diameter over that 11-year period. The line squiggles up and down on a yearly basis. That's expected, and has nothing to do with what's happening inside the sun. The Earth's elliptical orbit takes it closer to the sun in January and farther away in July.
Closer objects look bigger, so the sun appears slightly bigger in winter.
Changing temperatures also expand and contract the telescope itself, making it an unwanted zoom lens and further distorting the data. The size grew as the sun emerged from its last quiet period, peaking around 1990, then shrunk as its activity mellowed out. I was hoping for nothing. To me, it's a fly in the ointment. The variation in the sun's size coincides with its sunspot cycle.