Astronomers Find Ghostly Remains of a Turbulent Past around Quasars

Quasars are known to be super-energetic and compact regions surrounding a supermassive black hole at the center of a galaxy. Quasars usually get their luminosity and electromagnetic energy from the nearby black holes that spew back tons of energy in various forms while they feed on the mass from their surroundings.

But quasars have continuously puzzled astronomers due to their extreme brightness that reach us despite being located so far from our planet. On April 2, scientists had the chance to take a deeper insight into these baffling space objects as the NASA/ESA Hubble Space Telescope provided them with a set of images of so-called quasar ghosts.

“… eight unusual looped structures orbit their host galaxies and glow in a bright and eerie goblin-green hue.”

NASA reported that the eight green wisps flickered for a brief period of time before fading away. But over their short life, they offered important hints on the restless past of the galaxies that host the quasars.

NASA scientists explained that the eight elusive wisps caught by Hubble are the result of brief blasts of energy coming from the quasars. Quasars are very bright sources of light, but the light is not emitted evenly. As the central black hole of a galaxy gulps down the surrounding material, the materials start to heat up and form a quasar. But the energetic activity is not equal in all surrounding regions of a black hole. Instead quasars sometimes launch powerful jets of radiation and particles both upwards and downwards. These jets sweep through space just like a lighthouse beam does in the night.

Such jets of light briefly made dense filaments of gas to glow and create the ephemeral wisps Hubble has recently immortalized. Astronomers explained that the process is called photoionisation.

During photoionisation, the small gas particles within the gas filaments, which can contain helium, sulphur, oxygen, nitrogen and neon, absorbed quasar light and slowly released it back over many thousands of years.

NASA researchers argued that the green hue of the looped structures marks the presence of oxygen which glows green when it is ionized. Yet, the ethereal wisps are so far from the quasars that it took ten of thousands of years for the light to reach them and light them up. As a result, the green clouds continue to emit their light although their quasars had turned off.

Additionally, astronomers found that the green filaments are huge and some of them can even span tens of thousands of light-years. They are believed to be remains of two galaxies that had violently collided in a distant past. The event was so abrupt and forceful that it triggered enough gravitational forces to rip apart the galaxies and create long tails of gas.

In 2007, the Dutch astronomer Hanny van Arkel discovered the first gas filament of this kind. Prof van Arkel later reported it to the Galaxy Zoo project which listed it in the Sloan Digital Sky Survey catalog.

The bizarre ghostly structure was initially nicknamed Hanny’s Voorwerp which translates from Dutch as Hanny’s object.

Image Source: Boston News Time