Mystery of Quasars at last solved after 20 years

Quasars are the brightest entities in the cosmos, and display a mysterious variety in their look that has mystified astrophysicists for more than two decades.

Now, researchers find this secret can be cracked by looking at two simple characters of quasars — how rapidly matter is getting fed into the quasars and the orientation from which the quasars are observed.

Quasars are majestic black holes up to billions of times the mass of the sun that situate at the center of distant, enormous galaxies. They discharge extremely large amounts of light as they tear apart stars and eat up matter.

Past observations of quasars have discovered that the physical properties of the Quasars follow certain, consistent trends — for example, a quasar's size is related with its mass. Though, in spite of such trends, for some confusing reason, quasars can vary significantly in appearance in observable and ultraviolet light. 

To aid solve this mystery, researchers studied the largest sample of quasar observations yet — data from more than 20,000 quasars collected by the Sloan Digital Sky Survey. The collaboration's statistical analyses exposed that the look of quasars could typically be described by two basic aspects.

A quasar, the brightest type of object in the cosmos, is seen discharging massive amounts of energy as stars are torn apart near the enormous black hole of a galaxy in this artistic photograph.

"Our work solves a two-decade-long mystery in quasar research," said aa lead study writer Yue Shen, an astrophysicist at the Carnegie Observatories in Pasadena, Calif.

The first feature is the so-called Eddington ratio — the brilliance of a quasar related to its mass. This ratio forecasts how rapidly matter is falling into a quasar, and was long supposed to play a major role in why quasars frequently varied in look.

The other aspect is the orientation from which astrophysicists observe a quasar, which effects how much they can see of the clouds of gas nearby the black hole. This fast-moving gas yields a broad range of wavelengths of light, significantly altering a quasar's appearance, and these discoveries propose that these clouds are organized in a flattened disk, clarifying why the direction from which they are observed can be of so much importance.

"Our discoveries have deep implications for quasar research," Shen said in a statement. "This simple unification scheme offers a pathway to better comprehend how enormous black holes accrete matter and interact with their surroundings."

In addition, these discoveries will help develop future measurements of black hole masses, which in turn will help researchers better comprehend "the intergalactic growth of supermassive black holes and their role in galaxy creation," study co-writer Luis Ho at the Kavli Institute for Astronomy and Astrophysics at Peking University said in a speech.

Shen also mentioned there are several ongoing quasar studies that will deliver even more data "to enlarge the unification scheme established here." For example, this future data will help produce understandings on smaller black holes, "which are dimmer, and were overlooked in earlier studies," he said.



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