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When a dying star exhales it last breath, it’s a doozy. The star blows its outer layers of gas out into space. That surrounds the star’s core with a colorful bubble. The bubble can last for tens of thousands of years before it fades away.
One of those bubbles is on the edge of Gemini. The constellation is well up in the east as darkness falls. It’s marked by its brightest stars, the “twins” Pollux and Castor.
The Medusa Nebula is about 1500 light-years away, and it spans about four light-years. Some of the strands of gas that make up the nebula have reminded skywatchers of the snakes on the head of Medusa, one of the Gorgons of Greek mythology.
The strands have been expanding into space for thousands of years. They began their journey when their star could no longer produce nuclear reactions in its core. Gravity squeezed the dying core tighter, making it smaller and hotter. The radiation of the hotter core pushed away the layers of gas around the core. And they’re still expanding — more than 30 miles every second.
Ultraviolet light from the core “energizes” the gas in the nebula, making it glow. Different elements glow in different colors, allowing astronomers to identify them. That tells them about the original star, and about its demise.
The fate of the Medusa Nebula is shared by all Sun-like stars. So billions of years from now, the Sun will create its own nebula — a colorful bubble blown with its final breath.
Script by Damond Benningfield