Added 1 new A* page:The BBC article "Exploding stars left recent, radioactive mark on Earth" has a nifty illustration of the local bubble, the cloud of relatively hot but low-density gas, roughly 300 light years across, through which our solar system is currently traveling—this cloud is actually a cavity blown in the galaxy's pervading interstellar medium, which is on average ten times denser than the space inside the bubble.
According to the article, new studies looking at the distribution of iron-60, by far the most stable heavy isotope of iron—which comes, in theory, from the extreme fusion furnace of supernova explosion—both across the sea beds of Earth, and throughout the local bubble, suggest that particles from supernova explosions within 300 light years of Earth, ie probably within the local bubble (the aforementioned illustration of the bubble is in fact a 3D visualization modeling the distribution of iron-60 in our galactic neighborhood, in distinctly bubbly shapes), struck the Earth in "an increased smattering" from 1.5 million to 3.2 million years ago, and that these came from "a series of supernovae, one after another," that probably left the remnant we see as the local bubble today.
These explosions, particularly the two closest, taking place around 2.3 million and 1.5 million years ago, while "close enough to light up the sky as much as the Moon," would not have been close enough to cause mass extinctions on Earth, but still may have played a role in the evolution of life here.
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