How fast does the sun rotate on its own axis?

Answer

The rotational period of the sun is approximately (more details to follow) 29 days. We can see this from the movements of sunspots on the sun. Those sunspots arise and decay, but they stay roughly in the same place on the sun, so their movement is a good witness of how the sun rotates around its axis. And if we follow those sunspots, we soon see that the rotation period on the sun is not the same everywhere: it is shorter at the equator (25 days) and slower towards the poles (34 days). That tells us (as if we didn’t already know) that the sun has no solid surface. It is a rotating gas sphere with different layers that rub against each other. We see that on the surface, but that “differential rotation” also plays inside: deeper layers also have their own rotational period, and in turn rub with the layers above. Indeed, it is these relative movements within the gas sphere that is the sun that ensure that the magnetic effects they generate give rise to all kinds of spectacular phenomena.

How fast does the sun rotate on its axis? The period in which the revolution takes place is important there (that gives us the ‘angular velocity’), but also the distance to the axis around which the rotation takes place. On the (rigid) earth, the rotation period is the same everywhere, but the distance to the axis depends on where you stand: at the pole you simply remain standing, at the equator you move fastest. On the sun, the rotation period also depends on the location. So the answer to your question is not a single number. At the poles, the answer is zero kilometers per second. At the equator, a point describes the circumference of the sun (2pi times 700 thousand kilometers) in 25 days, so about 180 thousand kilometers per day or about 7500 km per hour. Faster than the rotation of the earth at the equator (40 thousand kilometers per day). And in between it depends on the latitude.

Yet we call the sun a ‘slowly rotating star’. Some other stars rotate much faster than the sun.