Astronomers have picked up what they say is the most distant signature of water vapor ever detected—from a region of space so far away that it took 11.1 billion years for light to travel from there to Earth. (The universe itself is only believed to be about 14 billion years old.)

Violette Impellizzeri, then a graduate student at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and her colleagues spotted the water vapor in a distant quasar by taking advantage of a process called gravitational lensing. The way a massive object—in this case a galaxy between the quasar and Earth—bends light, as described by Albert Einstein's theory of relativity, can allow it to function as a sort of "cosmic magnifying glass," as Impellizzeri put it.

Impellizzeri, now at the National Radio Astronomy Observatory in Charlottesville, Va., and her co-authors report their findings in the current issue of Nature.

Photograph of the 100-meter radio telescope used to detect water vapor in the early universe courtesy of the Max Planck Institute for Radio Astronomy