Flares

From Slackerpedia Galactica

A general term for a brightening of the light output of an object. Specific causes for flares vary depending upon the physical circumstances of that object. On Earth, we are most intimately acquainted with magnetic flares on our Sun -- solar flares. These are caused when magnetized regions of similar polarity bump into one another (which can happen because the Sun is a gas -- there is no rigid surface). Think of what happens when you take two bar magnets, and try to stick the north or south poles against one another -- they fly apart, right? On the Sun, what happens is that anything stuck between the two regions gets blasted out of the way as the two regions try to reconnect to their proper polarities. And blasted is an appropriate word: ions can be accelerated to several million electron volts, speeding them up to a fraction of the speed of light.

Solar flares are visible in X-rays, ultraviolet light, visible light, and down to the radio region of the spectrum. On occasion, flares are strong enough to blast stuff off the surface of the Sun and out into space. On rarer occasion, some of this stuff blows past the Earth, creating aurorae and very nervous satellite controllers. Other stars can have flares, and a type of variable star called a flare star can be fun to watch, with the right equipment. They're wee little stars, barely 20 percent of the mass of the Sun, and yet they can have the most spectacular flares. Since flares are very hot, they're also very blue, and since they're small, cool stars, they're normally very red. So when they have a flare, the amount of blue light they give off can increase enormously, to factors of 100 or more.

Fun fact: FRED is a type of flare. It's an acronym for fast rise, exponential decay. If you measure the time-variation of a flare, it may rise to peak brightness in a matter of seconds, and then fade over minutes or even an hour. So it looks like a sawtooth, not like Fred.