Quasars are among the universe's brightest fireworks. Scattered all across the sky, they blaze with the opulence of over 100 billion stars. And, like a brilliant July 4th aerial flare, they are dazzling for a relatively brief time — on cosmic timescales. That's because they're powered by voracious supermassive black holes gobbling up a lot of gas and dust that gets heated to high temperatures. But the quasar food buffet lasts only so long.

This fleeting characteristic of quasars helped astronomers find two quasars on a collision course with each other. They are embedded inside a pair of galaxies that smashed into each other 10 billion years ago. It's rare to find such a dynamic duo in the far universe. The detection yields clues as to how unsettled the cosmos was long ago, when galaxies more frequently collided and black holes were engorged with flotsam and jetsam from the close encounters.

Because the two quasars flicker at different rates as their inflow of fuel waxes and wanes, they were identified as an unusual activity happening out in space. Hubble zoomed in and clearly resolved the pair, as well as their host galaxies.

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