NASA's Hubble Snaps the Enigmatic 'Quasar Ghosts'
NASA's Hubble Space Telescope has captured dramatic images of a set of wispy, goblin-green objects, the ephemeral "ghosts" of quasars that once flickered into life and then faded.
The glowing structures have looping, helical and braided shapes. Scientists said they don't fit a single pattern.
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The ethereal wisps outside the host galaxy 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 searchlight shines into deep space. The beam is produced by a disk of glowing, superheated gas encircling the black hole.
"However, the quasars are not bright enough now to account for what we're seeing; this is a record of something that happened in the past," sid Bill Keel of the University of Alabama at Tuscaloosa, who initiated the Hubble investigation of the distant objects.
Keel believes the features offer insights into the puzzling behavior of galaxies with energetic cores.
He added the glowing filaments indicate those quasars were once emitting more energy, which they shouldn't do.
He suggests one possible explanation is the quasars may be co-orbiting black holes, which could change the quasar's brightness as they circle each other, acting something like a cosmic dimmer switch.
The first "green goblin" type of object was found in 2007 by Dutch schoolteacher Hanny van Arkel. She discovered the ghostly structure in the online Galaxy Zoo project.
The project enlisted the public to help classify more than a million galaxies catalogued in the Sloan Digital Sky Survey (SDSS), and moved on to add galaxies seen in Hubble images probing the distant universe. The bizarre feature was dubbed Hanny's Voorwerp, Dutch for Hanny's Object.
Keel's team took the galaxies that looked the most promising and further studied them by dividing their light into its component colors through a process called spectroscopy.
In follow-up observations from Kitt Peak National Observatory and the Lick Observatory, his team found 20 galaxies had gas that was ionized by radiation from a quasar rather than from the energy of star formation. And the clouds extended more than 30,000 light years outside the host galaxies.