Question

What assumption about sunspots is fundamental to determining the rotation of the sun by the sunspot method?

Answer 1

Sunspots are regions in the photosphere that appear dark. This is because they are cooler than the rest of the Suns lower atmosphere. This is because the magnetic field of the sun disrupts the surface and slows down the energy flow thus creating the cooler area and the sunspots. Due to this, sunspots usually arise in clusters. They are almost always found just north and south of the equator. The number of spots vary over a period of 11 years and a single spot can last anywhere between a few hours and a few months. The structure of sunspots is broken down into two sections. The umbra, the dark central region and the penumbra, the brighter ring, seen below and are approximately 10,000 km across.

The assumption is that sunspot is moving around the same latitude.