Is it possible for a planet to have very little visible-light energy and receive enough energy to support life from ionising radiation?
Dim light, including starlight and ionized-air glow is acceptable.

A planet in orbit around a binary star-black hole system:

  • High x-ray radiation
  • A star system could credibly have planets.
  • The creation of the black hole probably involved a supernova which could lead to planet creation.


  • Star will emit light.
  • The creation of the black hole probably involved a supernova which can destroy planets.

A rogue planet in a galaxy containing a Quasar

  • Possibly high radiation.
  • Planet can be in high period stable orbit within galaxy.


  • Quasars emit a lot of light.
  • Galaxies usually contain quasars in the early stages of their existence, when heavy elements are in short supply.

The planet could be covered in a thick atmosphere that blocks visible light but not high-energy radiation.

My question is; what scenario will maximize high-energy radiation but minimize visible light?

A related question is; what kind of life can evolve on such a planet?

EDIT: Since it seems to be impossible for the sky to be dark but flooded with radiation; what situation maximises the radiation-to-light quotient?

The situation I have in mind now is:

  • The planet was created in the aftermath of a supernova which turned one of the stars into a neutron star.
  • The neutron star has magnetic beams near (and heavily overlapping) the equatorial plane.
  • The neutron star slowly accretes matter from the other star, causing its magnetic poles to glow brightly in the x-ray and gamma-ray spectra.
  • The neutron star revolves every few seconds, sweeping the planet with regular bursts of radiation.
  • The planet revolves in an orbit aligned with the equatorial plane and relatively far from the parent stars.
  • The star looks relatively dim from that distance (to dim for photosynthesis).
  • Every few seconds, the atmosphere pulsates a blue light from air ionisation glow and the surface (including oceans) emits a bright flash of blue light from Cherenkov radiation.
  • Life first appears in the ocean, shielded by the protective layer of water.
  • Before the primordial soup runs dry, radiation resistant cells start to radiosynthesize and form thick curds on the surface.
  • Some life forms live underwater and come up to the surface in the night-time to graze on those curds, over many millions of years, they become quite complex.
  • Some radiation resistant life forms come to land to avoid overcrowding and predation.
  • Some of the more complex life forms venture onto land during the night-time and hide underwater before the next round of radiation.
  • Some of those life forms hide underground (in caves or artificial borrows) during the daytime, they are now fully terrestrial.
  • Intelligent life may or may not evolve.

How credible is this scenario?
One of the problems with my scenario is; how long will that setup last?

  • $\begingroup$ I would wager that the majority of orbits in galaxies with quasars will be bathed in limited amounts of radiation. As far as I know, most is emitted along the poles of the supermassive black hole, out of the plane of the galaxy. $\endgroup$
    – HDE 226868
    Feb 21, 2016 at 16:50
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    $\begingroup$ Sure, why not? We have no idea of the limits of life. $\endgroup$
    – King-Ink
    Feb 21, 2016 at 19:07
  • $\begingroup$ What's your definition of visible light. I bet if life could find a way to live in a high gamma/xray world it would also evolve to see in that range of the spectrum $\endgroup$ Feb 21, 2016 at 20:10
  • $\begingroup$ @RichardTingle With "visible light" I actually mean light with low enough energy not to break molecular bonds. $\endgroup$
    – k-l
    Feb 22, 2016 at 2:10
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    $\begingroup$ See Greg Egan's Incandescence. The Splinter world orbits a black hole and gets energy not from sunlight but from the types of radiation present. The title aludes to how it looks to senses adapted for that environment. $\endgroup$
    – JDługosz
    Mar 10, 2016 at 16:06

4 Answers 4


Most of the physics regarding quasars and pulsars etc has been explained by the people above me. Here I would go with a few quick fact check over the core of the question.

Q1- Is it possible for a pulsar planet (a planet revolving around a fast rotating neutron star) to harbor life?

Pulsar planets would be unlikely to harbour life as we know it, because the high levels of ionizing radiation emitted by the pulsar and the corresponding paucity of visible light. (https://en.wikipedia.org/wiki/Pulsar_planet#History)

Carbon based life, as we know it, relies on proteins for all biological processes. The sudden high energy X-ray beam from the pulsar would totally rip those molecules apart before the first prokaryote ever formed.

enter image description here A ghostly, beautiful world with dancing auroras ... and no life ...

Q2-Can a blackhole planet harbor life?

Theoretically yes (as this article states). But it would be a primitive type of life (if it carbon based life with metabolism similar to life on Earth) and there would be no complex life on such a planet.

Oh, the horror! p.s. this would be one of the most horrifying places to live at, in the whole universe ...

Q3- Can there be life on a rogue planet in a galaxy containing a quasar?

According to this article, containing an immensely knowledgeable video, it would depend on how far the planet is from the center of the galaxy/quasar. For example, considering that our solar system is present on the edge of our galaxy, if our galactic center turned into a quasar, its heat and light reaching us would be just 1% of the heat and light which reaches us from the sun. Counting this in perspective, the closer the planet is to the galactic center, the higher amount of heat and light it would receive from the quasar.

However, once again, heat and light alone are not the only determinants of life on a planet. Considering the extremely high energy gamma ray emissions and high energy particle jets emitted from the quasar, a planet which is at a distance to suitably be in the habitable zone of a quasar would probably get a frighteningly high amount of destructive radiation from it, which would destroy any and all life on that planet, reducing it to an apparently very habitable (in the goldillock zone) but in fact completely dead planet. Also, forget any shred of hope that an ozone layer could shield you from such high intensity energy beams. In fact those energy beams are powerful enough to easily destroy any ozone-like absorptive layer around the said planet.

!! I don't want to live on that planet. Period!

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    $\begingroup$ If the planet orbits at the proper "goldilocks zone" liquid water may exist (the probability of that, of course, is very small, but who wants to think about typical planets a.k.a. planets with no l). Most gamma rays are absorbed in the first 10cm, making the water glow brightly by Cherenkov radiation. Beyond that, there may be a layer of water kept liquid by conduction and possibly a primordial soup. Of course, I am being very optimistic. +1 The pulsar does look like the proper scenario. $\endgroup$
    – k-l
    Feb 22, 2016 at 12:32
  • $\begingroup$ Or there could be a different type of life on such planets. A life which is not carbon based like earthly life but some other sort of bizzare, primitive, alien life. "Life" is described as the genetic ability of an organism to harness energy from its surroundings and utilize it. It doesn't have to be carbon based life, the likes of which we see everywhere on earth. $\endgroup$ Feb 22, 2016 at 13:13
  • $\begingroup$ "planets with no l" I meant "planets with no life". Also, doesn't a pulsar require a nearby star to emit radiation? Even if it does not, the beams will likely miss the planet or only hit it for part of the year. Is there any source that emits high radiation in all direction? $\endgroup$
    – k-l
    Feb 22, 2016 at 16:56
  • $\begingroup$ Gamma ray bursts from supernovas go in all directions in 3 dimensions. And super-massive stars (which consume their stellar fuel much faster than our sun) are far more brighter and emit more frequencies of e.m. waves than our sun. Other than these, I think most celestial objects have particle jet emissions only in two dimensions. $\endgroup$ Feb 22, 2016 at 18:05
  • $\begingroup$ While many objects do emit tightly focused jets of radiation and particles around their axes, these won't have much effect on your planet unless it is in a polar orbit. In that case, radiation might be the least of your worries, these jets are moving at a high fraction of the speed of light and the relativistic beam would tear your planet apart. Only if there is no accretion disc will you get a dark sky, and without the accretion disc to feed matter into the body, you will probably not get the high energy jets from the axes of rotation either. $\endgroup$
    – Thucydides
    Feb 23, 2016 at 1:39

Can planets exist around black holes / quasars?

Yes. Black holes can be large enough to anchor entire galaxies - evidence strongly suggests a supermassive black hole at the centre of our own galaxy. Due to the increased mass of the black hole vs, say, a garden variety star, any planets would have to exist beyond the event horizon - which means if your planet is in orbit, it may already be a suitable distance from the black hole to avoid significant radiation.

Further, your planet could have been a rogue planet caught by the gravitational pull of the black hole after its supernova transformation, or a collection of debris from passing comments, meteors or asteroids.

Emissions - are they a problem to life on these planets?

This image shows a beam of xray and visible light being projected over a million lightyears from the pole of a quasar.

A quasar emitting a projection of x-rays

The jet is called an 'astrophysical jet' and contains x-rays as well as particulate matter and plasma, and for it to reach the escape velocity it must be travelling near to the speed of light. This would certainly cause problems for your planet. However, these jets tend to be emitted from the poles of the quasar/black hole, whereas orbiting bodies tend to move around its center of rotation.

X-rays and radiation may still be an issue, but not so much as an all-encompassing blast of planet-shredding plasma.

"It's life Jim, but not as we know it."

The main concern with a lack of visible light will come from nutrient systems. The vast majority of life on earth relies on sunlight as the keystone of the foodchain. However, there are places on earth (deep, underwater trenches) which rely on geothermal vents for energy. Plants and plankton there convert the planet's heat which comes boiling up through the water into nutrition, which larger, more complexed life (such as shrimp, crabs and tube worms) turn into energy for themselves.

Assuming the background radiation of your planet is enough to cause genetic mutations, death and cancers, it might be that any form of life on your planet has one, some or all of the below traits:

  • relatively simple (anything larger or more complicated is killed off by radiation or mutation)
  • self-correcting (DNA can repair mutations or cancers)
  • small (less surface area to reduce interaction with radiation)
  • radiation resistant (see below)
  • ground-dwelling or sea-dwelling (relies on physical protection from the environment)

There are some extremophiles that exist in real life, such as einococcus radiodurans bacterium, which can survive a 15,000 gray dose of radiation, where 10 grays would kill a human and 1,000 grays will kill a cockroach.

More complicated life exists in the form of fungi which can convert radiation into nutrients. From sciencedaily.com:

"Since ionizing radiation is prevalent in outer space, astronauts might be able to rely on fungi as an inexhaustible food source on long missions or for colonizing other planets," says Dr. Ekaterina Dadachova, associate professor of nuclear medicine and microbiology & immunology at Einstein and lead author of the study.

This source of nutrients would be a good option to support larger, more biologically complicated creatures which might live in networks of tunnels shielded from radiation by the density of the rock - making brief trips to the surface for food before returning underground. Again, deep water would have a similar potential for protection.

For further reading, I'd recommend looking into the species and lifecycles that continue to thrive around Chernobyl's reactor core.

TL;DR Yes, it's possible for ecosystems to exist without light and high levels of radiation. Life, uh... finds a way.

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    $\begingroup$ Hi Polyducsks. Welcome to Worldbuilding. Very interesting first post. Way to go :) $\endgroup$ Feb 21, 2016 at 20:33
  • $\begingroup$ +1 "X-rays and radiation may still be an issue" I want them to be present. Also, if the radiation all comes from one source and the planet is rotating, creatures could safely venture out in the "night-time" and hide before "daytime" starts. $\endgroup$
    – k-l
    Feb 22, 2016 at 2:20
  • $\begingroup$ "Emissions - are they a problem to life on these planets?" I want there to be emissions. What I don't want is to be stranded on that planet. $\endgroup$
    – k-l
    Feb 22, 2016 at 4:16
  • $\begingroup$ @KiranLinsuain I'm talking about those emissions/xrays being a barrier to life starting or continuing. Certainly a projected astrophysical jet would wipe out any form of atmosphere at minimum and at most would destroy the physical planet. Earth requires an atmosphere to prevent things such as meteors and other lethal background radiation - regardless of time of day. $\endgroup$
    – Polyducks
    Feb 22, 2016 at 8:45
  • $\begingroup$ @bilbo_pingouin Thank you so much :) It's a pleasure to be here! $\endgroup$
    – Polyducks
    Feb 22, 2016 at 8:50

The mechanism for radiation release around black holes and similar collapsed stellar remnants like neutron stars more or less preclude the possibility of having a dark sky full of ionizing radiation.

As matter is being pulled into the accretion disc, it is gradually being accelerated around the central object, and interacting with other particles also caught in the accretion disc. As the velocity and density increases, frictional forces heat the matter to higher and higher energies, which is where the problem comes in.

Matter at the outer edge of the accretion disk is fairly loosely gathered and moving relatively slowly, so the outer edge of the disc is going to be relatively cool. As we mover farther in, the amount of energy and density is going to become higher and higher, being re radiated at higher and higher frequencies. This means the disk is actually going to radiate in all frequencies from infrared to hard x-rays and beyond, so regardless of what you do, there will be a very large and bright visible component of energy being released from the disc.

Accretion disc

The movie Interstellar includes gravitational effects in their depiction of a black hole:

Interstellar movie black hole

Even from a very great distance the visible component is going to be quite brilliant; quasars are thought to be the central black holes of galaxies in the early stages of formation billions of years ago and are visible across the universe!

If we are considering a supermassive black hole near the centre of a galaxy, it will be dragging entire stars and star clusters around outside the accretion disc. Even if the area around the hole has become "cleared" for some reason, you will have the light of thousands or millions of stars streaming around the central black hole.

Small black holes near the end of their life are thought to emit energy in the form of "Hawking radiation", however since these are virtual particles being emitted from the event horizon (with their virtual partners in falling into the black hole), they will also be emerging at all energies in a random distribution, so the sky will become amazingly bright in the final few hours of the black hole's existence.

So living near a black hole will not be very dark at all....

  • $\begingroup$ An excellent point I hadn't considered! $\endgroup$
    – Polyducks
    Feb 22, 2016 at 8:47
  • $\begingroup$ All black holes are thought to emit Hawking Radiation all their life it's just more noticeable, also measurable, when they're dying because there's no accretion disk emitting radiation anymore. $\endgroup$
    – Ash
    Jul 27, 2017 at 15:46

Possibly an artificial Quantum Singularity, same class of object as a black hole but differently "arranged" could be build such that it captures it's own primary Hawking Radiation and re-emits it at non-visible wave-lengths. The biggest problem you really get into is that if you expose anything to enough hard radiation it will emit light, either through fluorescence, phosphorescence, or incandescence so your dark world is going to have to be right on the knife edge of having enough radiation to be usable but light enough that things don't glow like the sun anyway, and with most compounds there is at least one wave-length that causes one of these effects at relatively low intensity.

For some details on the fictional science of manipulating singularities "Cavitronics" have a look at David Brin's Earth.


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