For decades, scientists have been on the hunt for brilliant galaxies in the distant universe. These quasars were first noticed for being spectacularly bright – some of the most energetic objects ever discovered. But astronomers think many of them – in fact, the vast majority from the early universe – may be in hiding, camouflaged behind much closer galaxies.

Because of their brightness, astronomers want to use quasars to probe the era of reionization. This is a time less than a billion ye