They're not a crime-fighting team or a melodious singing group—the quasar quartet is a troupe of four incredibly rare celestial beacons surrounding a black hole that is nestled in the Lyman-alpha nebula.
Quasars appear around black holes. Due to their incredible mass and gravitational attraction, black holes greedily swallow up anything and everything that wanders in their path. Quasars emerge from all this heat and acceleration of matter. Kindled by the swirling mass flowing into the black hole, quasars look a lot like stars, burning fuel to create light. However, they have an edge over regular stars: They emit a broad range of light, wider than any star, and they are extraordinarily bright. Because they are powered by the colossal strength of the black hole, they burn intensely and brightly.
Quasars typically only last 10 million years; you may scoff at how large this number is and exclaim that it's actually an incredibly long time, but it's a thousand times shorter than the age of the galaxy that is around 10 billion years and counting. Were the galaxy to live a normal human life span, a quasar appearing in its center would last about the equivalent of an afternoon. Considering this brief window in which they appear, it's unlikely that humans will spot them in the majority of most galaxies. So to see four in one go seems like we've hit the jackpot!
The list of quasars has about 500,000 entries and out of these, only about 100 of them are binary quasars (pairs). The first ever triple quasar was seen in 2007, but now the astronomers have blown this record out of the water.
Because of the very low probability of ever seeing four quasars at one time, the astronomers wonder whether the nebula that the quasar quartet inhabits has some quasar-friendly conditions. Nebula Lyman-Alpha is in a portion of the universe that is unusually cluttered with galaxies. “There are several hundred times more galaxies in this region than you would expect to see at these distances,” explains J. Xavier Prochaska, professor at the University of California Santa Cruz.
"The giant emission nebula is an important piece of the puzzle," says Fabrizio Arrigoni-Battaia, a PhD student at the Max Planck Institute for Astronomy who was involved in the discovery, “since it signifies a tremendous amount of dense cool gas.” This is perfect fuel for a black hole to happily churn through. Any conclusions drawn at the moment are purely speculation, but it could be that nebulae, such as Lyman-Alpha, provide the perfect conditions to support quasar hotspots.