Ancient Quasar Enveloped by a Vast Water Vapor Halo

Astronomers modeling a diffuse reservoir of water vapor around the gravitationally lensed quasar APM 08279+5255 (redshift 3.91) report an inventory equivalent to about 140 trillion times Earth’s oceans, and a total water mass around 100,000 solar masses; the figure is model-dependent and hinges on lens magnification, gas excitation by infrared radiation, and the assumed molecular-gas mass. The detection relies on multiple water emission lines rather than a direct image or measurement of liquid water, and places water in the environment of a feeding supermassive black hole when the universe was about 1.6 billion years old, roughly 12 billion years in light-travel time. The result highlights water as a tracer of physical conditions in the early universe and underscores the uncertainties introduced by gravitational lensing.