3D view of the local bubble (white) and pieces of adjacent parts of the interstellar medium (purple and blue)
Did you know that we live inside a bubble? Believe it or not, the solar system, along with many other stars, sits inside what astronomers call the Local Bubble. It's a region of space that is less dense than the surrounding area of space, and contain very hot gas ( greater than 1,000,000 degrees!) that emit soft x-rays. Inside the bubble, space has about 0.01 hydrogen atoms per cubic inch (compare this to the ~10^20 atoms per cubic inch here on earth!). The bubble is shaped like an egg or a cylinder that is about 10x as tall as it is wide (30x200 parsecs), and sits upright with the plane of our galaxy crossing through the bottom third of the bubble. The solar system itself sits inside a thin sheet of cloud called the Local Fluff (no joke!), that is slightly more dense than the surrounding bubble. So where did this bubble come from? Astronomers are not a hundred percent sure, but the leading theory says that a supernova must have went off somewhere near the sun and essentially "blew" the bubble and heated up the gas inside. This probably happened around 10 million years ago, way after the sun and planets had already formed! So in a sense we survived a supernova explosion! Now the big question is this: are we living inside a supernova remnant that is still actively heating and removing material from the area? Or has the remnant material disappeared and left behind an "empty" bubble. Astronomers are actively trying to answer this question. But for now we are living happily in a sheet of fluff inside our own little galactic bubble!
