What are sunspots? Did you know that sunspots occur as a part of a cycle? The dark spots are extremely hot, but they appear to be dark, because they are relatively cool (almost 2,000K cooler) compared to the regions of the photosphere surrounding them. The parts of the spots are called the umbra and the penumbra, just like the darker and lighter parts of the shadows cast during eclipses, and sunspots can be larger than the Earth! However, these spots are not shadows. They are brighter than the a full moon appears. The Sun rotates differentially, meaning that part of it rotates faster than the rest, and this sort of rotation seems to wrap its magnetic field up like a cord (according to the Babcock model). Every 11 years, this causes the magnetic poles of the Sun to flip, meaning that its north pole becomes its south pole, and its south pole becomes its north pole. The surface of the sun has a "magnetic carpet" of looped magnetic fields, and as the surface rotates, turbulence whips up the gas and giant loops of ionized gases get flung out, and sunspots are what we observe of these disturbances. This is why sunspots always come in pairs, and they are the north and south "poles" of these loops. Every cycle, there are anywhere from just a few to over 100 sunspots, and the Maunder butterfly diagram which portrays the pattern the sunspots make is aptly named. These magnetic disturbances can be measured using the Zeeman effect, where an atom being passed through a magnetic field is able to absorb multiple wavelengths of photons, each representing the strength of the magnetic field. The magnetic field of a sunspot can be a few thousand times that of Earth's, and the cool temperature is thought to be caused because the fields may slow down the gas, which in turn slows down local convection. The heat is then thought to be deflected around the sunspot since infrared images also detect greater heat surrounding these spots. Interestingly enough, since we were discussing ice ages in class today, there was an extremely low record of sunspot activity in the sixteen and seventeen hundreds which coincided with a "mini ice age" in the northern hemisphere, which may or may not spell causation, but it is still compelling. We still do not understand the Sun's magnetic cycle, and it is something I would like to study. Some other magnetic phenomena of the sun include: prominences, which are giant loops of ionized gas trapped inside a magnetic arch that go through the photosphere, chromosphere, and even the lower corona; solar flares, which are strong enough to affect Earth's magnetic field and even disrupt navigation systems; and coronal holes, which is when magnetic loops break and do not reconnect with the Sun. This solar magnetic activity also causes auroras on Earth. Many other stars have starspots, but they are too far away to see. Through spectroscopic observations, however, we are able to study them and their magnetic cycles. By the way, I got all of this information from Foundations of Astronomy by Michael A. Seeds.
"All cannot live on the piazza, but everyone may enjoy the sun." -Italian proverb
4 points.
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