In July 2011, NASA’s Jet Propulsion Laboratory announced that two teams of astronomers had detected an enormous mass of water vapour around a quasar called APM 08279+5255, more than 12 billion light-years away. The quantity was put at the equivalent of 140 trillion times all the water in Earth’s oceans. JPL described it at the time as the largest and most distant reservoir of water ever detected in the universe.
The figure is real and the finding is solid. It is also more than a decade old, and the word “reservoir” carries an image that the actual object does not.
What was actually detected
APM 08279+5255 is a quasar, a galaxy with a feeding supermassive black hole at its centre. This one is extreme even by quasar standards: the black hole carries about 20 billion times the mass of the Sun, and the system radiates roughly as much energy as a thousand trillion Suns. That radiation floods the surrounding gas with infrared light and X-rays, heating it and lighting it up.
The water is in that gas, as vapour, spread through a region spanning hundreds of light-years. According to the JPL announcement, the gas is warmer and denser than the typical material between stars in a galaxy, which is part of why the water shows up so clearly. Two groups found it independently. A team led by Dariusz Lis at Caltech detected a single water signature in 2010 using the Plateau de Bure Interferometer in the French Alps. A team led by Matt Bradford at JPL then picked up several more spectral lines, which is what allowed them to estimate the mass. Bradford’s paper, “The water vapor spectrum of APM 08279+5255,” appeared in the Astrophysical Journal Letters. You can read the original JPL release for the full author list and figures.
Why “reservoir” gives the wrong picture
The number invites you to imagine a vast body of water, an ocean scaled up beyond comprehension. That is not what is there.
The 140-trillion-oceans figure is a total mass added up across a volume hundreds of light-years wide. Spread over that much space, the vapour is unimaginably thin by everyday standards. JPL described the gas as 300 trillion times less dense than Earth’s atmosphere, even though it is still unusually warm and dense compared with typical gas in galaxies. There is a great deal of water by total count because the region is so large, not because it is concentrated anywhere. The same logic lets you say the atmosphere contains an enormous tonnage of any trace gas you like: the total is huge, the local density is not.
The mass works out to around a hundred thousand times the mass of the Sun in water. That is a statement about how much material is in the region, not about how wet any part of it is.
What the light is showing us
The other thing the distance does is set the clock. Light from this quasar has been travelling for more than 12 billion years, so the gas is being seen as it was when the universe was young, well under two billion years after its beginning. The reservoir, as observed, belongs to the early universe. Whatever became of that gas in the time since is not something the measurement can tell us.
This is also where the significance sits, and it is worth being clear about what the scientists themselves said. Finding water was not the surprise. Bradford noted that water vapour was expected to be present even in the early universe, so its detection confirmed an expectation rather than overturning one. What the water provides is a tool. Its many spectral lines act as a tracer, letting astronomers read the temperature and density of the gas around the quasar and study conditions in a galaxy at that early epoch. The water is useful less as a headline and more as an instrument.
How firm is “largest ever”
A superlative like “the largest reservoir ever discovered anywhere in the universe” is a claim about our observations, not about the cosmos. It means the largest one detected so far, by instruments pointed at a tiny fraction of the sky, with a method that works best on bright, extreme objects like this quasar. The phrase describes the limit of what has been measured, not a survey of everything that exists.
The finding is now more than a decade old, which matters because “largest ever detected” is an observational record, not a permanent ranking of the universe. The result was striking when announced, and remains a useful reference point, but “ever discovered” should be read as “found to date,” not as a final tally.
What holds up is the underlying point that water, in the form of vapour, was already present in large amounts in the early universe, and that around an object as energetic as this quasar it becomes bright enough to study in detail. The ocean comparison makes the mass vivid. It is the early, diffuse, faraway nature of the gas that makes the measurement worth keeping.
