In July 2011, NASA’s Jet Propulsion Laboratory announced that two astronomy teams had detected an enormous reservoir of water vapour around the quasar APM 08279+5255. The agency translated the modelled mass into a number that is still repeated: roughly 140 trillion times all the water in Earth’s oceans.

The same account said the quasar released as much energy as a thousand trillion Suns. Both comparisons are grounded in published observations, but neither is as direct as it sounds. The “reservoir” is diffuse gas spread across hundreds of light-years, not a liquid ocean, while the quasar is magnified by a foreground gravitational lens.

This is also a 2011 result, not a new detection. Its interest now lies in what the measurements actually established about water in the young universe, and in how a handful of spectral lines became one of astronomy’s largest water comparisons.

The observations were fingerprints in radio light

APM 08279+5255 has a redshift of 3.91. Light from the system has travelled for roughly 12 billion years, so astronomers see it as it was when the universe was only about 1.6 billion years old.

Matt Bradford of NASA’s Jet Propulsion Laboratory led one of the teams. In a paper published in The Astrophysical Journal Letters, Bradford and colleagues reported six rotational transitions of water observed with Z-Spec at the Caltech Submillimeter Observatory in Hawaii. Their observing programme covered 13 nights between 2008 and 2009, totalling 25.3 hours, and one transition was checked with the CARMA radio array in California.

A separate group led by Dariusz Lis used the Plateau de Bure Interferometer in France. Its independent detection of an excited water transition arrived at the same redshift. That paper also gave a warning relevant to the giant mass claim: a single radiatively excited line does not provide a good water-abundance measurement on its own.

The telescopes did not photograph a pool or weigh the water directly. They measured radiation emitted at specific frequencies as water molecules changed rotational energy states.

The 140 trillion figure is a modelled inventory

Bradford’s team had several water lines plus carbon monoxide lines, allowing a broader model of the molecular gas. The authors compared the spectrum with that of the much nearer ultraluminous galaxy Mrk 231 and estimated an average water abundance of about 1.4 water molecules for every 10 million molecules of hydrogen.

That sounds sparse because it is. The total becomes enormous only because the region contains an extraordinary quantity of molecular gas. Combining the abundance with that gas reservoir led to the widely quoted equivalent of 140 trillion Earth oceans, or roughly 100,000 times the mass of the Sun in water vapour.

JPL’s original announcement described the gas as extending for hundreds of light-years around the central black hole. It had an estimated temperature near minus 53 degrees Celsius and a density far below Earth’s atmosphere, although it was warmer and denser than molecular gas typical of the Milky Way.

The ocean conversion is therefore an order-of-magnitude communication device, not a tank measurement. It depends on the adopted water abundance, the total molecular-gas mass, the excitation model and the correction for gravitational lensing.

The black hole is not what shines

A quasar is the luminous centre of a galaxy whose supermassive black hole is actively feeding. The black hole itself emits no light. Matter in the surrounding accretion flow becomes extremely hot as it loses energy and moves inward, producing radiation across much of the electromagnetic spectrum.

The 2011 JPL description assigned APM 08279+5255 a black-hole mass near 20 billion Suns and a luminosity comparable to a thousand trillion Suns. That is an energy-output comparison, not a statement that the object contains that many stars.

The water helped show what that radiation was doing to the surrounding galaxy. The Bradford paper modelled a region about 550 parsecs, or roughly 1,800 light-years, across. X-rays heated the molecular gas, while the intense far-infrared glow from dust pumped water molecules into higher energy states. Their subsequent transitions created the lines the telescopes detected.

In my reading, this is the more useful scientific result. Water was not merely present; it acted as a probe of the radiation field, density and temperature around an active black hole in the early universe.

Gravitational lensing complicates every giant number

APM 08279+5255 appears as multiple images because a foreground galaxy bends and magnifies its light. This is gravitational lensing, the same broad effect astronomers use in quasar time-delay measurements of cosmic expansion.

For this source, the magnification factor has been debated. Early work considered amplification around 40 or greater. The Bradford team adopted a later model with magnification around four. A lower magnification means the quasar must be intrinsically brighter and more massive to produce the observed signal.

The thousand-trillion-Suns estimate fits that lower-magnification picture. It should still be treated as model-dependent because changing the lens geometry changes the inferred intrinsic luminosity. The water mass and physical dimensions inherit related uncertainty.

Lensing does not create false spectral lines. It amplifies light that was already emitted. The secure conclusion is that water vapour was present at redshift 3.91; the lens model determines how the observed flux is translated into an intrinsic mass and luminosity.

“Twelve billion light-years away” is light-travel shorthand

For nearby objects, distance in light-years and the time light takes to arrive are nearly interchangeable. At redshift 3.91, cosmic expansion makes the language less tidy. The quasar’s light has been travelling for about 12 billion years, which is why NASA used “more than 12 billion light-years away.”

The galaxy is farther away now than 12 billion light-years in the present-day distance convention because space expanded while the light travelled. Astronomers use several distance definitions for cosmological objects, each suited to a different calculation.

The observational statement does not depend on choosing one popular-language distance. The measured redshift places the emission in a period when the universe was a small fraction of its current age.

The discovery was about conditions, not just quantity

Astronomers already expected water in the distant universe. Earlier generations of stars had manufactured oxygen, and ordinary chemistry could combine it with hydrogen. What the teams had not previously measured at such distance was a water spectrum revealing this much warm, dense and strongly irradiated molecular gas.

A related 2011 study led by Paul van der Werf detected four water lines in the same lensed quasar host. Its excitation model likewise found that intense infrared radiation dominated the higher-energy transitions and pointed to an obscured, star-forming nuclear region.

More lines and sharper lens models can refine the inventory. The firm result is narrower than the headline numbers but scientifically durable: water vapour was already abundant enough to trace the physical environment around a feeding supermassive black hole when the universe was about 1.6 billion years old.