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A low-density region of the interstellar medium within which the Sun is located. At the boundary of the "bubble", the gas density rises sharply by a factor of at least 10. The bubble boundary is nearest to the solar system in a direction roughly towards the galactic centre, where an extended dust cloud (known as Tinbergen's Cloud) lies about 30 light years away. The nature of this cloud is not well understood but it appears that its relative motion has led to a considerable deformation of the Local Bubble. The furthest extent of the bubble is about 500 light years away in the direction of the constellation Canis Major, where the bubble wall is permeated by tunnel-like structures. The Local Bubble was probably blown out by the shock wave from one or more supernova explosions that took place in our part of the Galaxy in the remote past.
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