Kepler, the invaluable telescope used to find distant worlds, or "exoplanets", has yielded new information on solar flares. It seems the sun isn't capable of summoning the very energetic solar flares seen in distant stars.
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The Kepler telescope uses an extremely precise photometer to scan distant stars. When it detects a tiny decrease in the light coming from the star, this could indicate a planet is moving between us and the star. Kepler will scan for several such dips before scientists can confirm whether or not a new planet has been detected. Because you can know the nominal brightness of a star, you can use the magnitude of the decrease to determine the size, orbital period, and orbital speed of the planet. This method is proving to be amazingly powerful.
However, it goes both ways. Kepler can also detect an increase in the nominal brightness of a star. When a star gets brighter, this means one of two things: a flare aimed directly at us, or a supernova. Supernovae very quickly make their presence known, so usually this increase is the result of a flare.
By scanning many such events, scientists have concluded that the sun does not produce very powerful flares. Even the most powerful one recorded, the 1859 Carrington Event (see post below), is puny compared to some of the more massive eruptions out there. Some flares from alien suns are probably 10,000 times more energetic!
It is a good thing that our sun is so docile. It is not hard to imagine a lonely bacterium, trying to make its way on a newborn Earth, being suddenly wiped out by a massive solar flare. Obviously, this might have prevented the continued growth of all life, and I might not be able to write this blog. Instead, it seems our sun is relatively quite, providing an ideal incubator for life to form.
It is curious to note that the sun was only 70% as bright as it is now during the days of the first bacteria. With such a weak sun, even the largest flares might not have had the power to sterilize the Earth. It seems that the bacteria simply got lucky.