I am using this discovery as my starting point (Source)

An international team of astronomers led by the California Institute of Technology and involving the University of Colorado Boulder has discovered the largest and farthest reservoir of water ever detected in the universe.

The distant quasar is one of the most powerful known objects in the universe and has an energy output of 1,000 trillion suns -- about 65,000 times that of the Milky Way galaxy.

The quasar's power comes from matter spiraling into the central supermassive black hole, estimated at some 20 billion times the mass of our sun....

Because the quasar -- essentially a voraciously feeding black hole -- is so far away, its light has taken 12 billion light years to arrive at Earth.

Since one light year equals about 6 trillion miles, the observations reveal a time when the universe was very young, perhaps only 1.6 billion years old.

Astronomers believe the universe was formed by the Big Bang roughly 13.6 billion years ago.

The water measured in the quasar is in the form of vapor and is the largest mass of water ever found, according to the researchers.

The amount of water estimated to be in the quasar is at least 100,000 times the mass of the sun, equivalent to 34 billion times the mass of Earth.

In an astronomical context, water is a trace gas, but it indicates gas that is unusually warm and dense, said Bradford.

"In this case, the water measurement shows that the gas is under the influence of the growing black hole, bathed in both infrared and X-ray radiation," he said.

"These findings are very exciting," said CU-Boulder Associate Professor Jason Glenn, a study co-author.

"We not only detected water in the farthest reaches of the universe, but enough to fill Earth's oceans more than 100 trillion times."

The water measurement, together with measurements of other molecules in the vapor source, suggests there is enough gas present for the black hole to grow to about six times its already massive size, said Bradford.

Whether it will grow to this size is not clear, however, as some of the gas may end up forming stars instead, or be ejected from the quasar host galaxy in an outflow.

enter image description here
Photo courtesy ESA/NASA, the AVO project and Paolo Padovani. Click on image to enlarge.

My Idea

I am designing a "quasar system" (analogous to a solar system). My quasar has a ring of predominantly water vapor with enough water that it could fill 14 trillion Earth oceans. Due to distance and heating from the quasar, the water is relatively warm (-63℉) compared to water found elsewhere in the universe. The ring has a radius of ten light years.

My problem is that I would like a planet with the following characteristics:

  • Ideally the size of Neptune.
  • Habitable and capable of supporting Earth-like flora and fauna.
  • It orbits through or adjacent to the water vapor ring.
  • It has deeper oceans than Earth. While Earth's oceans only make up about 0.02% of its mass (demonstrated by the image, below), I would like water on my planet to represent up to 0.09% of its mass, maximum.
  • The planet will be a traditional "water planet" with its ocean taking up 100% of the surface. Submerged landmasses can be allowed several hundred meters below sea level if they can exist.

enter image description here
Credit: Howard Perlman, USGS/illustraion by Jack Cook, WHOI

What am I handwaving?

  • I'm ignoring that such a planet can exist in a "solar" structure that's too young to host such a planet. (In other words, I realize that by the time my planet forms most of the water ring would have become stars or the whole quasar structure a proto-galaxy.)

  • I'm ignoring that such a planet would sweep its orbit clean of mass and that so much mass is available that it would eventually collect enough mass to become a star. This might require me to place the planet outside the orbit of the ring.

My Question!

Can my planet, orbiting within or near a ring as described by my source article, withstand the radiation of the quasar? I am using the quasar described in the article I source as my inspiration as the reference for this question.

Relevant questions that don't address my problem:

I found the following two questions that are relevant, but they do not address the problem I am trying to solve.

Edit: I didn’t know the measurements of the ring from the article so I stuck with the “10 lightyears” distance from the Sandbox. I’m more than happy to change the distance if it’ll help my planet’s chances, especially if it’ll make life possible on it.

  • $\begingroup$ Just stay outside of the accretion disc and you should be fine... 🤔 maybe. $\endgroup$
    – user6760
    Jan 2 at 7:05
  • $\begingroup$ "Since one light year equals about 6 trillion miles, the observations reveal a time when the universe was very young, perhaps only 1.6 billion years old." this is a weird sentence? $\endgroup$
    – ths
    Feb 28 at 8:49
  • $\begingroup$ Doesn't water block the majority of radiation pretty quickly? $\endgroup$
    – Zautech
    Mar 4 at 20:08

3 Answers 3


The simplest solution would be to move the planet further away, where water vapor will be more abundant and gas will naturally shield it from radiation. But first let's talk about the neighborhood the planet would find itself in 10 light-years from the quasar, based on the measured properties of that quasar, APM 08279+5255.

All the different types of active galactic nuclei, quasars included, are thought to have the same basic structure. Moving outwards from the center, most AGN have:

  • A supermassive black hole
  • A disk of hot gas being accreted by the black hole and emitting high-energy radiation, including x-rays and ultraviolet emission (with a radius on the order of light-days)
  • An area of fast-moving gas clouds, called the broad line region (~1 light-year)
  • A cold doughnut-shaped torus of molecular gas (~100 light-years)
  • An area of slower-moving gas clouds, called the narrow line region (~1000 light-years)

That said, the sizes and properties of the different regions do depend on the supermassive black hole and how it's behaving -- and so the environment 10 light-years from the center of APM 08279+5255 might be a bit different from the environment 10 light-years from the center of 3C 273.

I know you didn't choose a particular quasar, but let's use APM 08279+5255 as an example, since there's a lot we can say about its water content. We also know that the central black hole has a mass of $M\sim10^{10}M_{\odot}$ (Saturni et al. 2016), a luminosity of $L\sim5\times10^{15}L_{\odot}$ (Lewis et al. 1998), and surrounding gas totally $M_{\mathrm{gas}}\sim10^{11}M_{\odot}$ (Riechers et al. 2009) -- 10 times the mass of the black hole itself. Using a cool technique called reverberation mapping, we also know that the broad line region is about 1 light-year in radius (Saturni et al. 2016), a bit on the larger size for AGN but still what we would expect.

Your planet, located at 10 light-years, is likely near the edge of the broad line region but not far enough to be within or outside that gas torus that can shield from the high-energy radiation coming from the accretion disk. I did some playing around with a model called the Shakura-Sunyaev model and estimated that if the accretion disk extended all the way to the broad line region, the local radiation flux could be about four orders of magnitude higher than that received by Earth from the Sun -- and a significant amount would be in x-rays and UV. Even though the planet would be 10 times further away, it would still be affected by this emission; it would receive something like two orders of magnitude more light than Earth does. This would cause the planet to lose its water, much like how high-energy radiation from M dwarfs makes it hard for planets orbiting them to retain significant quantities of water (Ramirez & Kaltenegger 2014), or really anything resembling an atmosphere needed for habitability.

What you should probably do is simply move the planet further away, maybe to 100 light-years or so. The flux would naturally drop off because it would be further away from the accretion disk, and if there is a gas torus at that distance, it would block more of the radiation. The water vapor extends well over 1000 light-years from the quasar (Bradford et al. 2016), so at 100 light-years away it will definitely be present.

  • 1
    $\begingroup$ I couldn’t find a radius size for the ring in the article, so I stuck with whatever was suggested in the Sandbox. So, if moving it further will help the planet, then by all means let’s do it. $\endgroup$ Jan 2 at 16:14

The planet will be all in one piece , but life will be shizzled

Sure, quasars emit b*ttloads of gamma rays. Like if you were to stand near an average quasar, you could receive a radiation dose trillions or even quadrillions of times higher than you would by hugging the Elephant's Foot.

But aside from that, your planet will be intact, even without a ring. The gravitational binding energy of any planet the mass of Earth or even higher is way too much for the heat or radiation of a quasar to destroy. That includes water planets (as desired in the question), gas giants, Super-Earths etc etc.

Well, maybe not that much, you could still rip your water planet with heat, if you were close to the center of the quasar, like really close. However, at those distances, I would worry less about it getting vaporised by the heat, and more about being ripped apart by tidal forces near the quasar.

Long story short: A water planet is perfectly safe, in terms of the planet not being vaporised by a quasar.

However, if you are looking for a Habitable water planet, then your hopes are obsolete.

Quasars are not actually that deadly for life. In fact, recent evidence suggests that the Milky Way might have been a quasar about 6 million years ago, as proved by the existence of the Fermi Bubbles, two gigantic bubble-like structure emitting anomalously high amounts of X-rays and hard gamma-rays. However, the life on Earth is about as safe as Fort Knox. And the simplest explanation is usually the best explanation: Being far away.

The power of a quasar diminishes thanks to the saviour known as the inverse-square law, which means by the time the radiation has travelled a sufficient distance (perhaps on the order of hundreds of parsecs), it has already weakened out enough to not cause any appreciable damage to life. Sure, we would see a beautiful glow in the nightsky, and perhaps there would be a slight increase in background radiation, but that's about it. You would be as fit as a fiddle if you were just a few hundred parsecs away from the quasar. Earth, for comparison, is nearly 8000 parsecs away from Sagittarius A*, meaning that even during the time that the Milky Way was in a quasar phase, Earth was as fit as a fiddle, as it was way too far away to receive any significant radiation dosage plus, our atmosphere is opaque to hard-gamma rays, especially those which have been attenuated enough for a long time to have barely any effect.

However, your question suggests that the planet is really close to the quasar, like perhaps on the order of a few light-years or even AUs.

Your planet will be in one piece, but it will be as sterile as the Death Valley.

At really close distances, the intense gamma rays can overwhelm your planet's atmosphere, and a large fraction of them makes it to the ground. With intense radiation and heat, life as we know it would be impossible on that planet, as radiation would break down complex chemicals and therefore, the building blocks of life.

Your water ring won't be able to protect the lifeforms on that planet.

Atleast your water/ocean planet is all safe and sound :)

  • $\begingroup$ Hmm, what about life in the water? Water is an exceptional shield against radiation such as gamma rays. Could it mean that the surface/atmosphere of the planet is fried, but life could exist in the (deep) oceans? $\endgroup$
    – fgysin
    Feb 28 at 15:05

Have a shield planet, further in- some gas giant, throwing a massive magnetic cone, protecting you from solarwinds and using its mass to shield you from other radiation.

If its getting properly cooked, the gasgiant may even loose atmosphere, in a spiral, that drifts out towards your planet with its ice/water rign, having fency colors its glowing in.

PS: If your system drifts through the jet, its toast.


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