A star 40 times more massive than the Sun is blowing a giant bubble of material into space. In this colorful picture, the Hubble telescope has captured a glimpse of the expanding bubble, dubbed the Bubble Nebula (NGC 7635). The beefy star [lower center] is embedded in the bright blue bubble. The stellar powerhouse is so hot that it is quickly shedding material into space. The dense gas surrounding the star is shaping the castoff material into a bubble. The bubble's surface is not smooth like a soap bubble's. Its rippled appearance is due to encounters with gases of different thickness. The nebula is 6 light-years wide and is expanding at 4 million miles per hour (7 million kilometers per hour). The nebula is 7,100 light-years from Earth in the constellation Cassiopeia.