The Bubble Nebula is a beautiful bubble of gas (mostly hydrogen) blown by the stellar wind of a hot massive star that resides in its center. This hot star is around 45 times the size of Earth's sun, and Its incredibly hot gas escapes the star moving at over 4 million miles per hour, offsetting the cold gas around it and forming the outer edge. The nebula is located in the Cassiopeia constellation, at a distance of 7,100 light-years from Earth, and is 7 light-years in diameter, which is 150% greater than the distance between our sun to Alpha Centauri.