The surface of the Sun is like a pot of boiling water. Millions of bubbles of hot gas churn across it, constantly rising and falling. But the bubbles are a little bigger than those on your stovetop.

The bubbles are known as granules. They form as energy from deep inside the Sun works its way to the surface. That heats the gas in the Sun’s top layer, forming bubbles. As they reach the surface, their gas cools and drops back into the Sun. This non-stop activity creates an easy-to-see pattern of bright blobs – the hot gas – with dark lanes between them – the cooler gas.

The size of the granules varies from about a hundred miles to more than a thousand – big enough to swallow Texas. And each granule lasts for no more than about 20 minutes.

A recent study said the granulation changes a bit during the Sun’s 11-year cycle of magnetic activity. Just after the peak of the cycle, there are slightly more granules than average, but they’re a little smaller than average.

Other stars are so far away that we can’t see the granulation on most of them. But several types of observations confirm that they, too, are boiling away. Astronomers have seen granulation on a few stars. The stars are much bigger than the Sun. And they’re late in life, so they’re undergoing big changes. The granules on those stars are tens of millions of miles across – dozens of times the diameter of the Sun – giant bubbles of hot gas on giant stars.

Script by Damond Benningfield