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Hubble Space Telescope Spots Green Remnants of Colliding Galaxies

Green Ghosts
These Hubble Space Telescope images reveal a set of bizarre, greenish, looping, spiral, and braided shapes around eight active galaxies. NASA/ESA/W. Keel (University of Alabama, Tuscaloosa)

NASA's Hubble Space Telescope has imaged mysterious green wisps hovering around distant galaxies in what could be ghosts of quasars past.

The first of these mysterious structures was discovered by Dutch schoolteacher Hanny van Arkel in 2007. He found it while participating in Galaxy Zoo, an amateur research project where ordinary people classify galaxies online.

Intrigued, Bill Keel, an astronomer at the University of Alabama, Tuscaloosa, decided to investigate further. He enlisted 200 volunteers to look at 15,000 galaxies that were home to quasars. They found eight with the mysterious green objects.

How the Hubble Telescope Has Changed the Way We See Space 0:51

Each one was a different shape, with some looped and others braided or spiraled.

The green wisps are illuminated by blasts of ultraviolet radiation coming from quasars at the core each galaxy. Keel believes the strange objects are the remnants of colliding galaxies. Instead of being blasted out of the quasar, the gas ended up orbiting the remaining galaxy.

"We see these twisting dust lanes connecting to the gas, and there’s a mathematical model for how that material wraps around in the galaxy," Keel said in a statement. "Potentially, you can say we’re seeing it 1.5 billion years after a smaller gas-rich galaxy fell into a bigger galaxy."

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— Keith Wagstaff