Inhabitants of our Milky Way galaxy living several billion years from now will have a markedly different-looking sky overhead. Two brilliant objects, each as bright as the full Moon or brighter, will drown out the stars with their radiance. These giant blazing light bulbs are a pair of quasars, brought to life by the collision of our Milky Way with the neighboring Andromeda galaxy.

Quasars are ignited by monster black holes voraciously feeding on infalling matter, unleashing a torrent of radiation. The Milky Way and Andromeda have such black holes at their hearts, which are now sleeping giants. That is, until the big bang-up. The duo will be as deadly then as it is dazzling. Blistering radiation from the quasar pair might sterilize the surfaces of planets, wiping out innumerable extraterrestrial civilizations.

This tale of "death star" dueling quasars looming in the sky might seem like a scene out of a science fiction movie. But the real universe is stranger than fiction. This is actually a story that played out between two pairs of galaxies that existed long ago and far away. The galaxies, each containing a central, bright quasar, are in the process of merging. As the two galaxies in each quasar pair, move closer together, so do their quasars. Hubble caught the action, photographing two quasar pairs that existed 10 billion years ago, during the peak epoch of galaxy close encounters. The discovery offers a unique way to probe collisions among galaxies in the early universe that might otherwise have gone undetected. Ancient quasars are scattered all across the heavens, so finding these dynamic duos is fortuitous. Astronomers estimate only one in a thousand quasars are really double quasars. 

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