Sun Spots on the Sun
Written by Fraser Cain
NASA image of a sunspot up close.
The Sun is so bright you can't really look at it. But if you have the right filters and imaging equipment, you can see there are actually dark spots on the Sun. These are known as sun spots. They appear in a previously empty looking part of the Sun, stick around for a few days, and then disappear again. What's going on?
Although sun spots are darker than the surrounding regions of the Sun, they're actually incredibly hot. A sun spot can be more than 3,500 degrees Kelvin. Even though that would be white hot if you could look at it, that's less bright than the average surface temperature of the Sun, which is 5,800 Kelvin.
They're still working out the details of exactly what sun spots are, but here's what scientists know so far. Sun spots are regions on the Sun's surface which have incredibly powerful magnetic fields. They come in pairs, like the poles of a magnet, with one being the magnetic north sun spot, and then the other being the magnetic south sun spot. The magnetic field lines punch up through the Sun's surface and then connect the two sun spots together.
Astronomers think that the magnetic field lines inside the Sun get twisted around by the convection of hot plasma underneath the surface. Sort of the way that hot wax rises and falls inside a lava lamp. These magnetic field lines can get so twisted up that the pierce up through the surface of the Sun, called the photosphere, creating these sun spots. And then within a few days, the magnetic field reorients itself, and the sun spots disappear.
The number of sun spots on the Sun rise and fall over the course of an 11-year cycle. At the height of the cycle, there can be dozens of sun spots on the surface of the Sun at any time. And 11-years later, at the solar minimum, there are very few sun spots, and even times where astronomers can't find a single one.
We have written many articles about sun spots on the Sun. Here's an article about a strange lack of sun spots, and a time when the Sun burst to life.
If you want more information on sun spots, check out the website for NASA's SOHO space observatory.
We have also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.
Filed under: Astronomy
Tags: Solar System, sun, sunspots, the sun
