Bubble Nebula

The Bubble Nebula, or NGC 7635, is an enormous bubble being blown into space by a super-hot, massive star. The Bubble Nebula is 7 light-years across — about one-and-a-half times the distance from our Sun to its nearest stellar neighbor, Alpha Centauri — and resides 7,100 light-years from Earth in the constellation Cassiopeia. The seething star forming this nebula is 45 times more massive than our Sun. Gas on the star gets so hot that it escapes away into space as a "stellar wind" moving at over 4 million miles per hour. This outflow sweeps up the cold, interstellar gas in front of it, forming the outer edge of the bubble much like a snowplow piles up snow in front of it as it moves forward. The Bubble Nebula is being formed by an O star, BD +60°2522, an extremely bright, massive, and short-lived star that has lost most of its outer hydrogen and is now fusing helium into heavier elements. The star is about 4 million years old, and in 10 million to 20 million years, it will likely detonate as a supernova.