Astronomers: Quasar mystery solved after 20 years

 

Jonathan Marker | Science Recorder | September 15, 2014

 

aAccording to NASA, quasars exhibit a broad range of outward appearances when viewed by astronomers, reflecting the variety in the conditions of the regions close to their centers.

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According to a report from Carnegie Institution, quasars – the supermassive black holes that live at the center of distant massive galaxies – shine as the most brilliant beacons in the sky across the entire electromagnetic spectrum as a result of rapidly accreting matter into their gravitationally inescapable centers. Now, new research from Carnegie’s Hubble Fellow Yue Shen and Luis Ho of the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University have solved a quasar mystery that astronomers have been puzzling over for 20 years.

The complete research findings appear in the September 11 issue of Nature, and shows that most observed quasar phenomena could be unified with two simple quantities: one that describes how efficiently the hole is being fed, and the other that reflects the viewing orientation of the astronomer.

According to NASA, quasars exhibit a broad range of outward appearances when viewed by astronomers, reflecting the variety in the conditions of the regions close to their centers. However, despite this diversity, quasars have a surprising amount of regularity in their quantifiable physical properties, which follow well-defined trends discovered over 20 years ago. Shen and Ho solved this puzzle in quasar research: What unifies these properties into this main sequence?

Via the largest and most harmonized sample thus far of over 20,000 quasars from the Sloan Digital Sky Survey, combined with several novel statistical tests, Shen and Ho demonstrated that one particular property related to the accretion of the hole, called the Eddington ratio, is the driving force behind the so-called main sequence.

This ratio describes the efficiency of material fueling the black hole, the competition between the gravitational force pulling material inward and the luminosity driving radiation outward. This push and pull between gravity and luminosity has long been suspected to be the primary driver behind the so-called main sequence, and their work finally confirms this hypothesis.

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