Around 02:00 UTC last night (July 30, 2011), a sunspot named Active Region 1261 erupted with a short solar flare, which was caught by NASA's Solar Dynamics Observatory. Using Helioviewer I created a short video of the event:
[Make sure to set the resolution to at least 720p!] Those bright regions are actually sunspots, which are dark at wavelengths our eyes can see, but are quite bright in the ultraviolet. Solar flares
occur when the Sun's magnetic field lines get twisted up. They store a lot of energy, and when tangled they can suddenly snap, releasing that energy. Astronomers classify flares
by the energy released in X-rays, from Classes A,B, and C (weak) to M (moderate) to X (yikes!). This one was an M9, which is on the low high end of the M class. Powerful, but probably not enough to affect us here 150 million kilometers away. If anything, there may be a stronger than normal aurora in a day or two. The Sun's activity waxes and wanes on a roughly 11 year cycle, and we're on the upswing of Cycle 24. There was an unusually long quiet period after Cycle 23 and the start of this one, and the new cycle has been slow to rise. It's not clear what this means, although there is some evidence
this cycle may be weak. I am agnostic on this; the evidence is interesting but not conclusive. The Sun is fiercely complex, and its magnetic field even more so. The best thing we can do is continue to watch it and see what happens, and use that information to better our understanding of this nearest star to Earth.
Credit: NASA/SDO/Helioviewer. Tip o' the welder's goggles to Little SDO on Facebook.
Related posts: - Incredible solar flare video - kaBLAM! Footage of the X-class solar flare - Followup: Sunspot group's loopy magnetism - The Sun may be headed for a little quiet time - A fiery angel erupts from the Sun