A Hubble Space Telescope image shows NGC 7662, the Blue Snowball Nebula, which is the final act of a dying star. The star has expelled shells of gas into space. Ultraviolet energy from the star's hot core causes the gas to glow. Jets of material squirt away from the star's poles, forming streaks at the top and bottom of the image. [Mike Landherr /ESA/ESO/NASA]
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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.
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 miles per hour. Eventually, they’ll grow so thin that they’ll simply fade from view. After that, the star’s lonely core will stop producing energy. It’ll become a white dwarf — the small, hot corpse of a once-mighty star.
The Blue Snowball — also known as NGC 7662 — is in the constellation Andromeda, which spreads across the east and northeast this evening. You need a telescope to see the Blue Snowball — an electric-blue orb that’s announcing its own demise.
Script by Damond Benningfield, Copyright 2015