Sun Spot

A large sunspot group, Active Region 10904, is visible to the naked-eye. You can safely view it by projecting the image of the Sun through a telescope (as seen above) or by using a safe solar filter. Have fun sungazing. Click on the image for a larger view.

S&T: Steven Simpson

There's a nice big naked-eye spot on the Sun today, even though we're near the minimum of the 11-year sunspot activity cycle. Of course, when we're talking about the Sun, "naked-eye" means looking through a safe solar filter, such as a #14 rectangular arc-welder's glass. The spot (Active Region 10904, or "904" for short) is nearing the Sun's western limb and will rotate out of view in a couple more days.

On August 16th, a fairly minor solar flare (class C3) erupted at the spot, and Rogerio Marcon of Sao Paulo, Brazil, caught this picture of the flare in hydrogen-alpha light. (The flare consists of the irregular bright patches. These are the
footprints near the Sun's surface of magnetic fields dumping energy after they reconnected, or "short-circuited," at higher altitudes.)

The flare happened when the spot was facing directly toward us. Therefore the resulting coronal mass ejection should blow by Earth, buffeting our planet's magnetic field, on the 18th or 19th Universal Time, according to As a result, we may get a geomagnetic storm and possible auroras.


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