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What Are Quasars?
The nucleus of the Milky Way galaxy emits far to much energy to simply be a collection of stars. Astronomers think that a supermassive black hole powers the nucleus of our galaxy. There are many active galaxies that contain nuclei that are much more energetic than the core of our own Milky Way.
Astronomers call the nuclei of these very energetic galaxies active galactic nuclei (agn). Supermassive black holes also power agns. Quasars are the most extreme class of agns. They are among the most distant and luminous objects in the universe. There are no nearby quasars.
Because quasars are typically billions of light years away, we see them as they were billions of years ago. It is likely that the supermassive black holes that power quasars, other types of agns, and ordinary galaxies are initially very energetic but become less energetic as they age. Hence quasars are probably a very early stage in the evolution of their host galaxies. As the supermassive black hole ages and becomes less energetic, a quasar settles down into an ordinary galaxy.
Significance of the Triple Quasar Discovery
Astronomers think that galactic cannibalism (the merger of smaller galaxies into larger galaxies) plays an important role in the formation and early evolution of galaxies. A system of quasars is also a system of galaxies in an early stage of evolution; this triple quasar system is likely to be the very early stage of a galaxy merger.
By studying such systems, astronomers can gain insight into galaxy mergers or perhaps the formation of clusters of galaxies. Along these lines, Michele Fumagalli, one of this study’s authors told Decoded Science: “This rare event will help us understand the process of galaxy mergers.” Fumagalli added that the team is in the process of trying to acquire high resolution images of this triple quasar system to further study the system, saying: “Perhaps more interesting, the fact that we found three quasars in close proximity is likely unveiling the early stages of formation of a proto-cluster of galaxies ~10 billion years ago.”
This discovery will help astronomers understand galaxy mergers and the formation of clusters of galaxies.
Farina, E.P., et al. Caught in the Act: Discovery of a Physical Quasar Triplet. (2013). Monthly Notices of the Royal Astronomical Society.
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