4. Solar Flares
What is it? Solar flares are bursts of energy from the surface of the sun. Energy that is about 1/6 of the total energy the sun puts out every second. Roughly 160,000,000,000,000,000,000 Quintillion Tons or 160 Billions Megatons of energy. The flares, which are usually seen as a bright spot on the sun are followed by a huge amount of particles launched into space, called Coronal Mass Ejection, CME. The CME is what carries with it a variety of radiation types that travel to our world, like the gamma ray bursts we've talked about.
Is this common? Can I hide under a table to survive? There is a theoretical calculation for how many stars there are in the observable universe. This is based on the general number of observed galaxies multiplied by the general number of stars within those galaxies. That number is roughly 10 to the 24th power, 1,000,000,000,000,000,000,000,000 - 1 Septillion stars, give or take a few. In our suns case, it can have nearly a dozen flares a day, or roughly a couple in a week. On that math, Flares are quite possibly extremely common all over the universe. Most of the flares that occur from our star affect radio waves, communications, radar, and other technology that use satellites. However, there is always the possibility of a Solar Megastorm that can wreak havoc on a catastrophic level.
Has this happened before? Can it happen again? Their was a solar event in 1859 called the Carrington Event which was a Solar Megastorm that would have caused complete and utter destruction of most technology as it is today. A storm of this kind is predicted within a 10-12% probability to occur again in 2020. While it is not the type of storm that would create a massive enough flare that would carry strong enough Gamma Rays to erase our atmosphere, it will cause trillions of dollars in destruction, along with massive power and communications blackouts globally, and a number of other untold issues as a consequence. Predicted to possibly take 10+ years to recover technologically if it does occur. Our sun has an 11 year cycle for its activity, and based on that activity, it's most likely to have the most specific and consistent effects on our planet for some time to come before any other major killer in space actually comes to destroy us. While massive solar megastorms can wipe away our technology, and possibly annihilate our atmosphere, a Black Hole would actually "eat" our planet, sun, and solar system. Eat being a relative term.