The "Local Bubble" was probably created by a nearby supernova in the distant past.

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The most widely accepted theory is that the Local Bubble was created by a supernova that occurred 10 to 20 million years ago within 300 light-years of the Sun. This theory is supported by the presence of certain isotopes in the cosmic dust within the bubble. The most widely accepted theory is that the Local Bubble, a region of low-density gas in the interstellar medium surrounding our solar system, was created by one or more nearby supernovae that exploded between 10 and 20 million years ago.

The "Local Bubble" Was Probably Created by a Nearby Supernova