We would like to conclude our discussion of interstellar matter by asking how this material is organized in our immediate neighborhood. As mentioned earlier, orbiting X-ray observatories have shown that the galaxy is filled with hot bubbles, emit X-rays gas, resulting in a diffuse X-ray background that, from our perspective, seems to fill the entire sky. While part of this emission comes from the interaction of the solar wind with the interstellar medium, the majority comes from outside the solar system. The natural explanation for why there is x-ray emitting gas around us is that the sun itself is in one of the bubbles. That is why we call our “neighborhood” the Local Hot Bubble, or Local Bubble for short. The local bubble is much less dense (about 0.01 atoms per cm3 on average) than the average interstellar density of about 1 atom per cm3. This local gas is about a million degrees in temperature, as is the gas from the other super-bubbles spread around our galaxy, but since there is very little hot material, this high temperature in no way affects the stars or planets in it Area.
What caused the local bubble to form? Scientists aren’t entirely sure, but the main candidate is winds from stars & supernova explosions. In a nearby region towards the constellations Scorpius & Centaurus, a large amount of star formation occurred about 15 million years ago. The most massive of these stellars evolved very quickly until they generated strong-winds & some exploded with their lives. These processes filled the region around the sun with hot gas, displacing the cooler and denser gas.The expanding super-bubble reached the Sun about 7.6 million years ago and is now lies more than 200 light-years from the Sun toward the constellations Orion, Perseus, and Auriga.
There are some clouds of interstellar matter inside the local bubble. The sun itself appears to have entered a cloud about 10,000 years ago. This cloud is warm (with a temperature of approx. 7000 K) and has a density of 0.3 hydrogen atom per cm3. —Higher than most of the local bubble, but still so weak it is also known as the local fluff.
While this is a fairly thin cloud, we estimate that it contributes 50-100 times more particles than the solar wind to diffuse material between the planets in our solar system. These interstellar particles were discovered by the spacecraft traveling between the planets and their numbers were counted. Perhaps one day scientists will find a way to collect them without destroying them and bringing them back to Earth so that we can touch these messengers from distant stars, or at least study them in our laboratories.