Yesterday I talked about how water can form on the Moon. It might seem a bit surprising that water exists on the Moon, but it doesn’t sound like a crazy idea. What does sound crazy is the idea that there is water on the Sun’s surface, and yet we know that there is.
Wake Up Sunshine
We generally think of the Sun as a constant in our lives. It rises and sets regularly, and seems to be an unchanging sphere of brilliant light. In fact the Sun has a turbulent surface with prominences that fly off its surface, granules caused by convection in its upper layers, and even the appearance of slightly cooler regions known as sunspots.
Common Core
Our Sun (like other stars) is powered by nuclear reactions within its core. Part of the way we know this is through the observation of solar neutrinos. When solar neutrinos were first observed, the levels observed were less than predicted by about a factor of three, which came to be known as the solar neutrino problem. Since then we’ve come to understand that neutrinos have mass, and can change between flavors (electron, muon, and tauon), which solves the solar neutrino problem. Our neutrino detectors are good enough that we can now produce neutrino images of the Sun, such as the image above, and the rates of neutrino emission are in good agreement with solar core models.
Oh God, Oh God, We’re All Gonna Die
Recently there’s been a flurry of articles about an increase in solar activity, including rumors that Edward Snowden had revealed the NSA knows of a solar flare “killshot” set to cause a global famine that will kill millions. The rumor has since been traced back to a satirical website, but that didn’t prevent the story from being repeated across the internet. The story has flared up again in the past few days on new that NASA has reported the Sun has emitted a coronal mass ejection (CME) in the direction of Earth.
You Could Have Died!
Growing up I was a bit of a risk taker. Along with a few of my friends, I occasionally did things that (while very cool) were in retrospect notoriously dangerous. Occasionally my Mom found out about these activities, which worried her to no end. As she put it, “You could have died!” This is absolutely true. Some of the stunts we pulled could have ended in serious injury or death. It is also true that my friends and I survived childhood largely unscathed. The reason I bring this up is because recently there has been a flurry of stories about solar activity in 2012, and the headlines are much the same “You could have died!”
Blemish
Sunspots are dark regions that appear on the surface of the Sun. Despite their appearance, sunspots aren’t actually dark. They are cooler than the surrounding surface, which means they are less bright. When an image of the Sun is made dim enough to view directly, either by viewing the Sun through a filter or by projecting the Sun’s image onto a surface, the cooler, dimmer sunspots appear dark.
That’s So Random
Imagine you were standing in the center of a circle 100 meters in radius. How long do you think it would take to leave the circle? Usain Bolt could do it in 10 seconds, but most people could leave the circle in under a minute. After all, it’s just a casual 100 meter stroll and you are out of the circle. But suppose we added a rule that you couldn’t simply walk in a straight line. Suppose after each step you were required to change to a new random direction. Take a step, random direction. Another step, another random direction. You can’t control your direction, all you can do is take a step. Random turn, step, random turn, step, etc. Now how long would it take you to leave the circle? A minute? Ten?
Fire, Burn and Caldron Bubble
From Earth the Sun looks calm and never changing. It is a constant that rises and sets on schedule. Of course we now know that the Sun is quite active, with sunspots, prominences and solar flares. There are also more subtle changes on the Sun’s surface. One of these is an effect known as granules, seen in the image above.
X Factor
A solar flare is an intense burst of energy released at the surface of the Sun. It is caused by a process known as magnetic reconnection. The rotation of the Sun occurs at different rates depending on latitude. It has a rotational period of about 25 days at its equator, but about 34 days near the poles. This means the equatorial regions of the Sun rotate faster than the polar regions. Because of this differential rotation, the magnetic field of the Sun is twisted, so that over time the field lines of the magnetic field gradually wrap around the Sun.