Quasars have provided a series of mysteries for astronomers since they were first discovered. One of these is centered on their diverse appearance, a characteristic which astronomers have worked to understand for over 20 years. Differences between otherwise-similar quasars are visible in both ultraviolet and visible wavelengths of light.
Diversity in the appearance of quasars may be explained by two factors - the rate at which matter is falling into the body, and the angle at which it is seen from Earth, according to new research.
Quasars are black holes with masses millions or billions of times that of the Sun, that live in the central cores of distant, and therefore ancient, galaxies. As stars and interstellar matter falls toward the bodies, the region surrounding quasars light up, releasing vast amounts of energy.
The bodies have been found to follow certain general trends. For instance, the size of the celestial objects are dependent on their mass.
Data from 20,000 quasars, collected during the Sloan Digital Sky Survey, was examined, searching for clues to explain diversity among the massive black holes. Statistical analysis was applied to the massive quantity of information examined.
The Eddington ratio compares the luminosity of a quasar to its mass, in an effort to determine the rate at which material is falling into the body. This ratio was believed to play a part in determining the appearance of the supermassive black holes.
Clouds of gas falling into the black hole are responsible for the massive amount of energy radiating from quasars. This new research determined this material exists as a disk encircling the massive body. This shape would reveal different amounts of radiation when seen from various angles.
"Our findings have profound implications for quasar research. This simple unification scheme presents a pathway to better understand how supermassive black holes accrete matter and interplay with their environments," Yue Shen, from the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, said.
As matter falls into a quasar due to gravity, the material is pushed back by radiation pressure from the area surrounding the black hole. This push-and-pull balances into an equilibrium, driving steady glow.
Study of quasar diversity could assist astronomers in learning more about the evolution of black holes.
"[B]etter black hole mass measurements will benefit a variety of applications in understanding the cosmic growth of supermassive black holes and their place in galaxy formation," Luis Ho, researcher on the project, told the press.
Investigation of quasar diversity and how observations could be affected by accretion rate and the angle of observation was detailed in the journal Nature.
