Local Environment

Our solar system is a bit like a Russian matryoshka doll. It’s inside an interstellar cloud, which in turn is inside an interstellar bubble.
The bubble, known as the Local Bubble, spans a few hundred light-years. It was carved out millions of years ago by the shockwave and radiation of one or more exploding stars. There’s much less gas and dust inside the bubble than in the surrounding galaxy. But the gas that does fill the bubble is much hotter than the surrounding galaxy — also the result of the exploding stars.
The Local Interstellar Cloud is inside the bubble. Its gas and dust are denser and cooler than the bubble, although less dense than many other interstellar clouds.
The solar system is moving through this cloud at tens of thousands of miles per hour. As a result, a breeze of helium atoms blows through the solar system at that same speed. The Sun’s gravity focuses the breeze into a long tail that’s downwind of the Sun. Earth passes through that tail in December, so right now we