Since the discovery of quasars in the 1960s, astronomers have considered them among the most mysterious and luminous objects in the universe. Initially, they appeared to be extremely bright stars, but it was later revealed that they are the centers of distant galaxies fueled by supermassive black holes that devour enormous quantities of gas and dust.
Today, after more than six decades of research, artificial intelligence is contributing to opening a new chapter in the study of these objects, after a team of researchers succeeded in discovering seven rare quasars that may help explain how giant black holes grow and galaxies evolve throughout the history of the universe.
This artist's concept depicts the brilliant light of two quasars residing in the cores of two galaxies that are in the chaotic process of merging. (Image credit: NASA, ESA, and J. Olmsted (STScI))
The study's findings were published on July 22 in The Astrophysical Journal and were based on data from the Dark Energy Spectroscopic Instrument (DESI) project, with the participation of researchers from Ohio State University in the United States.
Cosmic lenses reveal what galaxies hide.
The study focuses on a rare type of quasar that simultaneously acts as a natural gravitational lens. The quasar's gravity bends light coming from a more distant galaxy behind it, magnifying it and revealing details that are difficult to observe under normal conditions.
This phenomenon is a valuable scientific opportunity, as it allows researchers to observe the quasar and the distant galaxy simultaneously, something that is usually difficult to achieve, since the enormous light emitted from the quasar overwhelms the light of the galaxy that hosts it, obscuring many of its details.
Five lensed quasars that were found in this work. All of which are represented in the literature.
Five quasars subjected to gravitational lensing in the shape of an "Einstein cross" were discovered by researchers and confirmed by observations from the Hubble Telescope.
"Quasars are like childhood images of supermassive black holes, so understanding how they evolved into the giant black holes we see today is critical," says Everett MacArthur, lead author of the study and graduate student in astronomy at Ohio State University.
This analogy suggests that quasars represent an early and active stage in the life of black holes, when they are at the peak of their growth and consumption of the surrounding matter.
Artificial intelligence searches among 800,000 quasars
Finding these rare systems has been a huge challenge, because instances of quasars aligning with a galaxy so far away that they act as gravitational lenses are very rare in the universe.
To overcome this difficulty, the researchers used a machine learning algorithm to analyze data from about 800,000 quasars observed by the DESY project, one of the largest modern astronomical projects to map the universe.
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