Hubble Peeks at the Green Ghosts of Space

The Hubble Space Telescope recently captured images of some eerie and beautiful objects floating around space. A series of green and ghostly wisps were recently spotted by the unmanned orbital telescope, betraying the past presence of quasars, the brightest objects in the Universe.

As far as astronomers understand them, a quasar is the exceptionally luminous region of compacting matter that surrounds the supermassive black hole at the center of your average galaxy. As clouds of galactic material (stardust, gas, etc.) fall towards the black hole, they become more and more compact, heating up to a point where they begin to glow. This can form the brilliant quasars Hubble sees, which beam powerful jets of radiation away from the rotating disks of matter.

So what does this have to do with the green ghosts? According to the European Space Agency (ESA), which manages the Hubble Space Telescope in collaboration with NASA, the ghosts are actually wispy once-invisible filaments of oxygen, helium, nitrogen, sulfur, and neon located on the furthest outreaches of a galaxy. Because of their location, it takes a long time for a quasar's radiation to reach them, but when it finally does, the filaments absorb that light, and start to glow eerily (ionized oxygen in particular glows green). (Scroll to read on...)

And what's most eerie about these wispy structures is that they are like ghosts - fading reminders of quasar light long after the luminous center of the galaxy has grown cold and quiet.

"These ghostly structures are so far from the galaxy's heart that it would have taken light from the quasar tens of thousands of years to reach them and light them up," the ESA explained in a recent release. "So, although the quasars themselves have turned off, the green clouds will continue to glow for much longer before they too fade."

The glowing wisps are thought to be trails of gas left over from clashes between galaxies long ago - a phenomenon that experts are becoming more familiar with. These most recent wisps were identified as part of a crowd-sourced effort, using 200 volunteers to examine over 16,000 galaxy images from the Sloan Digital Sky Survey. Researchers then analyzed highlighted structures to find 20 galaxies in all that contained glowing ionized whips.

The results can be found in the Astronomical Journal.

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