Big Sunspot Bows Out With A Bang

Giant sunspot 2529 is seen just inside the sun's western limb this morning by NASA's Solar Dynamics Observatory. The sun's rotation will carry it around to the other side in the next two days. If it survives, we may see it again at the sun's eastern limb in two weeks. Credit: NASA/SDO
Giant sunspot 2529 is seen just inside the sun’s western limb this morning by NASA’s Solar Dynamics Observatory. The sun’s rotation will carry it around to the other side in the next two days. If it survives while out of view, we may see it again when it rotates around to the sun’s eastern limb again in two weeks. Credit: NASA/SDO

Giant sunspot 2529 has provided a lot of entertainment this past week for solar observers. Several times the diameter of the Earth, the sunspot was easily visible through a #14 welder’s glass and a stunning sight through even the smallest telescopes. Most beginners think of telescopes as night sky instruments only, but they’re just as useful in the daytime equipped with a safe solar filter. Daytime observing has other advantages: it’s warmer, you can see your way around and it’s easier to stay awake.

In far ultraviolet light, the big flare from 2529 stands out in spectacular fashion. It occurred yesterday around 7:40 p.m. CDT. Credit: NASA/SDO
In far ultraviolet light, the big flare from 2529 stands out in spectacular fashion. It occurred yesterday around 7:40 p.m. CDT. Credit: NASA/SDO

Sunspots are patches of the solar surface where magnetic energy is concentrated. They’re dark because the intense magnetic fields insulate the area from the rest of the broiling, seething surface, cooling those areas by several thousand degrees. Compared to their hotter surroundings sunspots only appear dark. Cut one out and float it against the blue sky, and it would appear blindingly bright.

On April 13, the big spot's dark umbra resembled a heart. Credit: NASA/SDO
On April 13, the big spot’s dark umbra resembled a heart. Credit: NASA/SDO

The giant spot behaved itself during most of its run with only minor flaring, but as if to remind us not to get too complacent, it fired off a strong M6.7-class flare early yesterday evening. Ultraviolet light from the explosion ionized Earth’s upper atmosphere, disrupting shortwave communications on the planet’s day side for a time yesterday.  Usually, when a flares blows off near the sun’s limb, it’s not aimed in our direction and we don’t get swept up in its subatomic flotsam and jetsam. But occasionally, a cloud of particles will make a glancing blow at Earth’s magnetic envelope and spark auroras.

We’ll have to wait and see if that might happen with the most recent explosion. Now that its magnetic fields have become more complex, more large flares are expected from the giant spot even as it rides out of sight.