A new and respectably large sunspot has been rotated in sight of the Sun’s face, which in any case would be interesting as the sun has been very quiet for several years. But what makes this even more remarkable is that solvents predicted that this would happen, even when this place was on the other side of the sun!
Sunspots are areas on the surface of the sun with intense magnetic strength. Normally, large packages of ionized gas (called plasma) inside the sun rises through the interior due to their heat, and when they reach the surface they cool and fall down again. This is pretty much what happens when you heat a pot of soup as well (thought it was a liquid and not plasma).
However, if the magnetic field embedded in the plasma becomes tangled when it reaches the surface, the packet cools but cannot sink again. It remains, and because it is colder than the surrounding material, it appears dark: a sunspot.
The sun also goes through cycles of magnetic activity, which manifests itself in a way that increases and decreases the number of sunspots over time. It goes from minimum to maximum and back to a min over about 11 years. Cycle 24, the last one, ended last year and cycle 25 started in September 2019.
Some spots have appeared on the sun, but on November 23 a new one peeked over the western edge of the sun and rotated in sight. It was already decently large, which means that it was formed on the far side of the Sun, which we can not see from Earth.
But that does not mean that researchers have no idea what is happening over there. In fact, they become quite good at predicting what is happening on the far side of the Sun. They knew this place was there long before we could actually see it.
It depends on a field called helioseismology. On Earth, seismic waves are sound waves (more technically) acoustic waves) traveling through the earth. By measuring them, we can find out how deep the earth’s interior is (that’s how we know there are layers like the core and mantle down there).
Same with the sun. All the raging activity on the surface of the sun and deep inside it creates acoustic waves that travel around. As they do, the surface of the sun vibrates like a drum. By accurately measuring these vibrations, scientists can now only tell what is happening inside the sun, but also on the other side.
The magnetic fields that permeate the sun disturb these waves, and so they can also affect what is seen. That’s how the researchers knew that this place – called Active Region 12786 – was coming around. The signal for that did not appear until November 14, but it was weak and was not large enough to base any claims on. But it grew rapidly and in just one day it was large enough to be considered a solid discovery.
And for sure, on November 23, it became visible when the sun’s approximately month-long rotation slowly took it in sight from the earth.
The site itself is about 40-50,000 kilometers wide. It is easily three times wider than the earth! If you threw the earth in place, it would not even touch the sides.
To be clear, this type of prediction has been made many times before; just a few weeks ago, they predicted active Region 12781, which was visible in the sun after it was also rotated in sight. What makes this new cool is that the sun is so quiet that the signal from 12786 was very clear and that it is a great place. We usually do not see such large ones until well into the new cycle. I would not read too much about it for now; the sun is mercury* and it can be difficult to know what it is doing in a particular cycle.
But this type of thing is important to know. Magnetic fields in the sun can be quite festive and they store a lot of energy. It can be released in large explosions called solar flares, and even larger ones called coronal mass ejections. Both of these can cause real damage to satellites in orbit around the earth and cause extensive power outages on the earth’s surface (they can create large flows of electricity below the surface, geomagnetically induced currents, which puts a lot of stress on generators and power distribution).
When that happens, I saw the sites from AR 12781 about a week ago, and another group (AR 12783) just the other day; I have a pair of binoculars that are specially designed to look at the sun. DO NOT ever look at the sun without proper help, especially with things like binoculars or telescopes unless you know what you are doing. And even then, you have to be very careful, unless it is desirable to fry the retinas and boil glasses in your eyes.
Instead, you can view the current solar observations from NASA’s SOHO online, including the image with visible light. Another good site is Solar Monitor, as well as current images from the Solar Dynamics Observatory.
And remember: the sun may seem familiar and friendly, but it is actually a ball of nuclear-powered boiling plasma well over a million kilometers above, and its magnetic field can literally be connected to ours even from over 150 million kilometers away. We rely on it for warmth and light, but we really need to keep an eye on it if it decides to throw a little more in our way.