Discovery of the First Quasar Quartet Ranked Among the Top 5 Space Stories of 2015

February 12, 2016

Published in May 2015, the discovery of the first Quasar Quartet by a team of astronomers led by Joe Hennawi from MPIA was ranked number four in Astronomy Magazine’s top 10 Space Stories of 2015.

This comes just a year after a previous discovery involving Hennawi and MPIA graduate student Fabrizio Arrigoni-Battaia was named by “Physics World” to be one of the top ten breakthroughs of 2014.

Image of the region of the space occupied by the rare quasar quartet. The four quasars are indicated by arrows. The quasars are embedded in a giant nebula of cool dense gas visible in the image as a blue haze. The nebula has an extent of one million light-years across, and these objects are so distant that their light has taken nearly 10 billion years to reach telescopes on Earth. This false color image is based on observations with the Keck 10m telescope on the summit of Maunakea in Hawaii.

Quasars constitute a brief phase of galaxy evolution, powered by the infall of matter onto a supermassive black hole at the center of a galaxy. During this phase, they shine as the most luminous objects in the Universe. However, quasars are exceedingly rare on the sky, and are typically separated by hundreds of millions of light years from one another. Which is why the discovery of four quasars in close physical proximity to each other came as such a tremendous surprise.

Clues about the origin of this unusual object come from the peculiar properties of its environment. The four quasars are surrounded by a rare giant nebula of cool dense hydrogen gas - which the astronomers dubbed the "Jackpot nebula", given their surprise at discovering it around the already unprecedented quadruple quasar. In addition, both the quartet and the surrounding nebula reside in a proto-cluster of galaxies – a rare corner of the universe, 10 billion light years away, with a surprisingly large amount of matter.

Piecing all of these anomalies together, Hennawi and collaborators speculated that both the abundance of dense cool gas signified by the nebula as well as the more frequent collisions with nearby galaxies in the proto-cluster make quasar activity much more likely to occur.  "Extremely rare events have the power to overturn long-standing theories," says Hennawi. As such, the discovery of the first quadruple quasar may force cosmologists to rethink their models of quasar evolution and the formation of the most massive structures in the universe.

The quadruple quasar discovery was ranked at number four in the top-ten, below the New Horizons spacecraft’s close encounter with Pluto, the first-ever comet landing by the Rosetta mission’s Philae spacecraft, and the discovery of a X-ray emitting cloud near the center of our Milky Way galaxy.

For more information on this study, please see the MPIA news release of May 14, 2015 at

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