Hubble Discovers Wispy, Phantom Green Objects Near Dead Quasars

Scientists have discovered a set of wispy, green objects that are the ghosts of quasars that flickered to life and then faded away. The unusual structures may shed some light on the puzzling behaviors of galaxies with energetic cores.

The glowing structures have looping, helical and braided shapes. Spotted with NASA's Hubble Space Telescope, these structures are believed to have been illuminated by powerful ultraviolet radiation from a supermassive black hole at the core of the host galaxy. The most active of these galaxy cores are called quasars, where infalling material is heated to a point where a brilliant light shines into deep space. This beam of light is produced by a disk of glowing, superheated gas circling the black hole.

"However, these quasars are not bright enough now to account for what we're seeing; this is a record of something that happened in the past," said Bill Keel, one of the researchers, in a news release. "The glowing filaments are telling us that the quasars were once emitting more energy, or they are changing very rapidly, which they were not supposed to do."

It's possible that co-orbiting black holes are powering the quasars, and this could change their brightness, like using the dimmer switch on a chandelier. The quasar beam caused the once visible filaments in deep space to glow through a process called photoionization. Oxygen atoms in the filaments absorb light from the quasar and slowly re-emit it over many thousands of years.

The researchers believe the green filaments are long tails of gas pulled apart like taffy with the help of gravitational forces due to the merger of two galaxies. They also believe that the quasar variability may be explained if there are two massive black holes circling each other in the host galaxy's center. This could happen after two galaxies merged.

The findings are published in the Astronomical Journal.

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