In a way, the object known as the Blue Snowball Nebula is hosting its own wake. It’s announcing its demise in boisterous fashion. The object is a planetary nebula — a colorful bubble of gas and dust surrounding a star’s dying heart. Such an object forms after the core of a star has consumed its original hydrogen fuel, and begins to create energy by “fusing” other elements. That causes the star’s outer layers to first puff up to giant proportions, and eventually to blow completely away from the star and out into space. Blue Snowball Nebula [Wikimedia]And that’s what’s happened to the Blue Snowball. Over the last few thousand years, the star has expelled gas into space in waves. Those waves form three distinct shells around the star. The extremely hot core emits lots of ultraviolet energy, which causes those shells of gas to glow like a fluorescent bulb. The shells contain a lot of oxygen, which gives the nebula its blue color. The shells of gas are expanding at hundreds of thousands of
