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A Pulsar Habitable Zone?

Life and pulsars don’t seem to mix. But science fiction hasn’t shied away from making the connection, as witness Robert Forward’s Dragon’s Egg (Ballantine, 1980). In the novel, a species called the cheela live on the surface of a neutron star, coping with a surface gravity 67 billion times stronger than that of Earth. An interesting consequence: The cheela live at an accelerated rate, going from the development of agriculture to high-tech in little more than a month, as perceived by the human crew observing the course of their rapid development.

Now we have news that two astronomers are considering habitable planets in orbits around pulsars, a venue that to my knowledge Forward never considered, but perhaps more recent science fiction writers have (let me know if you have any references). Alessandro Patruno (Leiden University), working with Mihkel Kama (Leiden and Cambridge University) see reasons for thinking that life might emerge in such an environment, though the kind of atmosphere that would sustain it would be like nothing we’ve yet encountered.

The paper defines three categories of neutron star planets while explaining the conditions they would be subjected to:

Neutron star planets can be first-, second- or third-generation. First generation planets would be formed in the usual manner, as a by-product of the star formation process, and would likely be ablated or unbound during stellar death. Second generation objects would form in the supernova fallback disk around a freshly-formed neutron star. Third generation planets would form from a disk consisting of a disrupted binary companion (possibly previously overflowing its Roche lobe), thought to be essential for producing millisecond pulsars such as B1257+12. The supernova explosion, the accretion from a companion for millions up to billion years that MSPs [millisecond radio pulsars] undergo, and the emission of high energy X-ray/γ-ray radiation and MeV–TeV particles (the pulsar wind) are all disruptive processes that might destroy planets or disrupt their orbits.

In any case, neutron stars deal out bursts of X-rays and other particles, accreting matter around them and boasting huge magnetic fields. This is a very dicey environment, one would think, to be talking in terms of habitable zones. But in their paper in Astronomy & Astrophysics, Patruno and Kama find room for a habitable zone as large as 1 AU in breadth. To make this work, the planet must be a super-Earth with a mass between one and ten times that of Earth. Also required: An atmosphere a million times as thick as Earth’s.

Daunting conditions indeed. The work draws on studies of the pulsar PSR B1257+12, famous for its three known planets, which were the first exoplanets ever discovered, in 1992 (the third was found in 1994, still a year before the discovery of 51 Pegasi b). Aleksander Wolszczan and Dale Frail will forever be associated with the discovery. Patruno and Kama used the Chandra space telescope to study PSR B1257+12, which is 2300 light years out in Virgo.

Image: This artist’s concept depicts the pulsar planet system discovered by Aleksander Wolszczan in 1992. Wolszczan used the Arecibo radio telescope in Puerto Rico to find three planets – the first of any kind ever found outside our solar system – circling a pulsar called PSR B1257+12. Pulsars are rapidly rotating neutron stars, which are the collapsed cores of exploded massive stars. They spin and pulse with radiation, much like a lighthouse beacon. Here, the pulsar’s twisted magnetic fields are highlighted by the blue glow. All three pulsar planets are shown in this picture; the farthest two from the pulsar (closest in this view) are about the size of Earth. Radiation from charged pulsar particles would probably rain down on the planets, causing their night skies to light up with auroras similar to our Northern Lights. One such aurora is illustrated on the planet at the bottom of the picture. Credit: NASA/JPL-Caltech/R. Hurt (SSC).

What we have around this pulsar are two super-Earths with masses between 4 and 5 times that of Earth, orbiting the pulsar at 0.36 and 0.46 AU respectively; the third, innermost planet is about twice as massive as the Moon. The pulsar itself shows a mass of 1.4 times the Sun’s, with a radius estimated to be in the range of 10 kilometers. All three planets are close enough to be heated by the pulsar, a daunting thought given the X-ray radiation and relativistic ‘pulsar wind,’ which could have devastating effects on a planetary atmosphere.

Nonetheless, the paper continues:

… the two Super-Earths may have retained their atmosphere for at least a hundred million years provided they contain a large atmospheric fraction of the total planet mass, with the atmosphere possibly still being present to these days. We also find that if a moderately strong planetary magnetosphere is present, the atmospheres can survive the strong pulsar winds and reach survival timescales of several billion years. The same argument applies to possible pulsar planets around more powerful objects than PSR B1257+12.

We are talking about a planet that would have an atmosphere accounting for about 30 percent of the planet’s mass. In this news release, the authors liken conditions on the surface of such a world to the deep sea floor here on Earth. Says Patruno: “According to our calculations, the temperature of the planets might be suitable for the presence of liquid water on their surface. Though, we don’t know yet if the two super-Earths have the right, extremely dense atmosphere.”

That pulsar wind remains tricky on several levels. It is not an indefinite process, but one that turns off once the pulsar reaches a slow enough rate of spin. The paper points out that young pulsars turn off the pulsar wind within about a million years, while millisecond radio pulsars do the same in about a billion years. Losing the pulsar wind turns off the planet’s energy source and would cause a dramatic drop in temperature, unless tidal heating, radiogenic effects or X-ray radiation can step in in a process called Bondi-Hoyle accretion, analyzed in the paper:

Isolated neutron stars are directly exposed to the interstellar medium and it is expected that all of them would accrete some of this material. Such accretion process generates extra power due to the conversion of the accreted gas rest mass into energy, with a typical efficiency of the order of 10–20%. This so-called Bondi-Hoyle accretion process should be continuous and might be the main source of power for these type of systems.

I’m thinking science fiction writers among our audience (of which there are more than a few) might want to look at this paper to see what kind of scenarios they can tease out of it. Bear in mind that to this date, we’ve found but five pulsar planets, out of some 3000 pulsars studied. But exotica are what science fiction thrives on, and the kind of habitable zone depicted here is made to order for the hard science fiction writer willing to dig into this paper’s equations.

Addendum: Didn’t Alastair Reynolds deal with a neutron star planet in the first book of the Revelation Space sequence? I need to revisit the series. Wonderful stuff.

The paper is Patruno & Kama, “Neutron Star Planets: Atmospheric Processes and Irradiation,” Astronomy & Astrophysics Vol. 608, A147, published online 19 December 2017 (full text).


Comments on this entry are closed.

  • Al Jackson December 20, 2017, 11:32

    You know I wonder if Forward got the cheela from Ted Sturgeons’s Microcosmic God (1941)? The Neoterics, a microscopic created artificial life form live at an accelerated rate and create an advanced technology giving the story a very mysterious ending. Boy 1941, there are more modern SF stories that ‘shade’ this idea, but lord!, 1941!, Sturgeon was a remarkable thinker and writer, he was not alone in the 1940s. Alas if only TV and movie science fiction could give those guys some credit!

  • Douglas Loss December 20, 2017, 11:43

    I think calling such hypothetical planets “habitable” is something of a stretch. “Habitable” usually connotes the ability of humans to exist on the planet for at least the medium term as a self-supporting society (I don’t think this is just a connotation I alone make). In this case I think “potentially life-supporting” would be more accurate than “habitable.”

  • Chris S December 20, 2017, 12:29

    Hades from Revelation Space. From the RS wiki:


    > Hades was one-half of a binary system with its partner, Delta Pavonis, which was ten light-hours away. The sole object to orbit it was a moon, Cerberus.

    > Apparently a simple neutron star, later investigation by the crew of the Nostalgia for Infinity discovered that it was, in fact, a massive alien computer. Linked to Cerberus through a portal — theorized by Dan Sylveste as possibly being the phenomenon that’s study had given the Shrouders their mastery of space-time warping — it was able to sample individuals who passed through and create sentient simulations of them. It was also able to communicate with its past and future incarnations.

    > Originally, after the star’s supernova, a black hole was created. However, at some unknown point in the future, someone — or something — began a process that injected particles at particular rotations along its event horizon, which caused them to travel back through time — as time and space had become merged concepts so close to the gravity well. Having no effect on past moments of the black hole itself, it did effect its pre-black hole incarnation. During the supernova, instead of collapsing into a black hole, it formed a paradoxical structure unlike anything else in the universe.

    > A neutron star, at least the crust of one, formed by strange quarks and degenerate neurons. The new creation was capable of lighting-swift computation and possessed the theoretical maximum density of storage of matter.

    > During their war with the Inhibitors, a faction of the Banished fled into Hades.

    > Nearly a million years later, Dan Sylveste and his wife Pascale also entered the construct.

  • Michael December 20, 2017, 12:52

    Paul I think you mean 1.4 the mass of the Sun.

  • Stave December 20, 2017, 13:16

    Larry Niven: The Integral Trees (1984) and The Smoke Ring (1987). I do not have them to hand and am afraid I cannot remember the tap dancing Niven did to set up the environment or whether the star was described as a pulsar. Was there a large planet orbiting a neutron star which created and controlled a gas torus in which the action takes place?

    • Joe December 20, 2017, 15:56

      Here you go:


      The gist is a binary system (T3/Voy) with a gas giant (Gold) close to the neutron star’s Roche limit, enough to disrupt its atmosphere but not its rocky core. The secondary provides heat & light. I think Niven stressed the neutron star was old and quiescent (!pulsar) while the gas giant’s disruption was relatively recent. I doubt the air pressure and other habitable conditions in the Smoke Ring’s core are plausible, but as a kid I found this setup more fascinating than Ringworld.

      • Paul Gilster December 20, 2017, 17:09

        Good stuff, Joe. Thanks. I should have remembered The Smoke Ring.

    • Paul Gilster December 20, 2017, 17:10

      Stave, I have The Integral Trees around here and The Smoke Ring as well, but couldn’t dredge the memory up re pulsars. Thanks for the reminder!

  • Ron S. December 20, 2017, 13:43

    “millisecond radio pulsars do the same in about a billion years”

    I recall that all millisecond pulsars are formed by accreting matter from a close companion star, by addition of angular momentum, since the usual process that forms a neutron star cannot achieve spins that rapid. That would seem to make habitability a problem before, during and after accretion is exhausted, regardless of a planet’s attributes.

    • Joe December 20, 2017, 16:05

      That’s where the generational formation schemes come into play. I think from an early date everyone agreed PSR B1257+12’s planets couldn’t be first-generation as they were in too close to survive the supernova. Second-generation formation would leave the problem of how to spin up the pulsar without disrupting the planetary system. Third-generation would account for the spin-up and conceivably leave enough material in orbit for planetary formation without further disruption.

  • andy December 20, 2017, 16:06

    I seem to remember that in Alastair Reynolds’s Galactic North (also part of the Revelation Space series) some groups of humanity evacuate to pulsar planets to escape the Greenfly machines.

    I’m very sceptical about the possibility for habitable planets around pulsars. Besides, we’re coming up on the 26th anniversary of the publication of the discovery paper of the PSR B1257+12 planets and since that time there’s been a notable lack of discovery of similar systems, despite the sensitivity of pulsar timing as a method of finding exoplanets.

    • J. Jason Wentworth December 21, 2017, 7:59

      Yes–I think the odds of finding silicon-based life (which is a thoroughly low-probability, but entertaining, science fiction concept [the Tholians of “Star Trek” are just one, better-known example]) is greater than that of finding life residing on pulsar planets, but:

      Nature, being far more ingenious than we give her credit for, is responsible for all sorts of things that were “impossible”–or so improbable as to seem so–until human beings discovered them. Bacteria that have partly replaced carbon with sulfur (and can live happily in boiling sulfuric acid) and the lifeforms around deep ocean “black smokers” are just two examples. (I would not be shocked if aerial lifeforms, perhaps microscopic, are someday found in the atmosphere of Jupiter, or even of Venus.) Also:

      While missions to these planets (or to a pulsar planetary system–if one were close enough to reach, and we had the necessary space hardware to do so) whose *primary* purpose was to find life would not be scientifically or financially sensible, because of the low odds of finding life there, keeping an open mind–and eyes–would be prudent. The history of science is replete with “incidental,” serendipitous discoveries which were made while looking for–or looking at–something else. Not uncommonly, the “incidental” discoveries turned out to be more significant than the original work, and in this connection:

      Including spin-scan “push broom” imagers on atmospheric probes for Jovian-type planets would be useful for meteorological, nephelometric, and atmospheric optics research concerning these worlds (to name just three “orthodox” investigations). But for all we know, such imagers might also show aerial creatures similar to the hypothesized “floaters” and “hunters” that Carl Sagan covered in “Cosmos,” and such a discovery would rock the world, both in and of itself, and because of its implications for life elsewhere, and likewise:

      An additional regular series of radio emissions from a pulsar planetary system, particularly if they were narrow-band (or especially, if such laser–even X-ray laser–emissions were detected), their possible non-natural ramifications should not be reflexively brushed aside because “it just can’t be.” (In his paper about possible alien interstellar messenger probes, Dr. Ronald N. Bracewell pointed out that Jupiter’s extremely powerful radio emissions were heard–and ignored as terrestrial radio interference–for *decades* before their extraterrestrial origin was discovered, in the mid-1950s; it was inconceivable that such a large cold body could generate radio waves.) What other world-changing discoveries might already be on the cusp of being discovered, or even now be lying in plain sight, waiting for their sensational nature to be recognized?

  • John walker December 20, 2017, 16:27

    Off topic.
    A Christmas gift from the American Geophysical Union:
    Whilst searching for a certain presentation on magsail deceleration, I looked up the AGU on YouTube. For those interested, the AGU is in the process of releasing from the looks of it every presentation from AGU Fall Meeting 2017 onto YouTube. In full. They’ve released over 250h worth of material thus far. That’s over 1000 presentations. With more to come? The presentation I wanted to check out from Anthony Freeman isn’t there yet.

    A great move on their part. I hope this becomes standard. I like watching these things. It’s a nice change from reading papers.
    The videos aren’t labeled well so
    go to the AGU website if you are looking for something specific. The codes for the videos you want will be listed. Search by subject or name.
    Glein for Europa and Enceladus.

    • Paul Gilster December 20, 2017, 17:07

      This is wonderful news. Let’s hope it’s a spur to other organizations to keep the videos coming.

  • Adam Crowl December 20, 2017, 17:08

    Inductive heating is one energy input they’ve not mentioned. Apparently it can be significant around Red Dwarfs, so it should be even more so around a pulsar!

  • Geoffrey Hillend December 20, 2017, 17:18

    It’s hard to imagine what kind of life could live under a pressure of a million atmospheres which is what the pressure is 10,000 miles into Jupiter’s atmosphere, the pressure where pressure ionization begins to create metallic hydrogen, a density that makes hydrogen conduct electricity and create Jupiter’s magnetic field.

    Also the surface of a neutron star is composed of electrons which are separated from the neutrons to make protons due to the extreme centrifugal force. These electrons are flung out through the magnetic poles and form synchrotron radiation in the form of x rays. Quarks can’t become separated at a surface temperature of the neutron star of only a few million degrees kelvin. There are no free quarks on the surface of a neutron star. Quantum field theory forbids the separation of quarks at low temperatures. Try proton collisions in the LCH which is something like 3 trillion degrees which can for a very small fraction of second form a quark-gluon plasma.

  • Geoffrey Hillend December 20, 2017, 17:20

    The centrifugal force is caused by the fast rotation of the neutron star.

  • Michael Fidler December 20, 2017, 23:11

    Something interesting I came across when looking at Dyson Spheres around white dwarfs is the discrepancy in what mass the original stars that formed them and at what mass they would become a neutron star. The Tolman–Oppenheimer–Volkoff limit says the original stars are between a stellar mass of 15 to 20 solar masses but the Chandrasekhar limit for white dwarfs says some where between 4 to 8 solar masses to make a core that is 1.4 solar mass, anything above that forms a neutron star. See below:
    Star types, masses and lifetimes:

    The Milky Way has numerous regions and open star cluster where these large stars form and live their short life, in their death blowing out the many elements that make us tick. The distant but bright blue to blue-white stars we see at night are this type, they are rare and short lived. Because of their short lifespan and possible when the Milky Way became a starburst galaxy for short periods of time after merging with dwarf galaxies there should be many neutron stars, pulsars and magnetar then we presently see.

    These left over remnants could become the home to Dyson sphere civilizations around both neutron and white dwarfs. The big problem is the radiation and structural strength of the sphere. What about an inflatable sphere with an inside atmosphere pressure large enough to hold the immense structure in place and have enough gas between the pulsar and the inner surface of the Dyson Sphere to change the radiation into heat?

    Then all you need is a Dyson Vacuum to fill it up. ;-)

    • Michael Fidler December 21, 2017, 11:09
    • Michael Fidler December 22, 2017, 10:17

      One of the unusual aspects of white dwarfs is that as the mass increases the white dwarf becomes smaller, so small that any star that has a mass at around 4 to 8 suns will end up as a white dwarf of around 1.4 mass of the sun, but with a diameter of only 200 MILES! The question is how small of a Dyson sphere could be built around such an object? A rough calculation from Ibrahim Semiz∗ and Salim O˘gur “Dyson Spheres around White Dwarfs” using the Table 1 on page 12, the Dyson Sphere could be as small as 60,000 miles.

      The blast from the original star will cause a planetary nebula to form and the core left will be made up mostly of carbon and oxygen. The debris left around the white dwarf will also be made up of mostly carbon and oxygen. This could easily be made into a multiple Layer Graphene Dyson Sphere that will become Diamond-Hard from any external impacts.

      This is also both flexible and inflatable so the oxygen and hydrogen around the white dwarf could be used to make an atmosphere inside the Dyson sphere. You can find many science fiction novels that deal with something like this on a smaller scales. The main point is that using a material that can be inflated like a balloon but will not be punctured would solve the problem that plagues Dyson Spheres and that is structural strength.

      The Bigelow Expandable Activity Module (BEAM) on the space station could be leading the way to the development of Dyson Spheres.


      • Michael Fidler December 22, 2017, 22:07

        Christmas Ornament Planetary Nebula.

        Beautiful large image of the Milky Ways planetary nebula’s with names and IDs, for your children or the child in you!


      • Michael Fidler December 28, 2017, 10:51

        The White Dwarf that’s not there, PSR J2222-0137.

        This may be the first real Dyson Sphere!!!

        This object is one of nearest pulsars at 850 light years from earth and the white dwarf should be easily visible in the infrared .

        “Earth-Sized Diamond” –A White Dwarf Fossil Same Age as the Milky Way Found Orbiting a Neutron Star.


        Remarkable white dwarf star possibly coldest, dimmest ever detected.
        By applying Einstein’s theory of relativity, the researchers studied how the gravity of the companion warped space, causing delays in the radio signal as the pulsar passed behind it. These delayed travel times helped the researchers determine the orientation of their orbit and the individual masses of the two stars. The pulsar has a mass 1.2 times that of the Sun and the companion a mass of 1.05 times that of the Sun.
        These data strongly indicated that the pulsar companion could not have been a second neutron star because the orbits were too orderly for a second supernova to have taken place.
        Knowing its location with such high precision and how bright a white dwarf should appear at that distance, the astronomers believed they should have been able to observe it in optical and infrared light.
        Remarkably, neither the Southern Astrophysical Research (SOAR) telescope in Chile nor the 10-meter Keck Telescope in Hawaii was able to detect it!!!



        • Michael Fidler December 28, 2017, 11:23

          A Massive-born Neutron Star with a Massive White Dwarf Companion.

          This is the latest on PSR J2222-0137, from July 2017.

          We report on the results of a 4-year timing campaign of PSR J2222−0137, a 2.44-day binary pulsar with a massive white dwarf (WD) companion, with the Nançay, Effelsberg and Lovell radio telescopes. Using the Shapiro delay for this system, we find a pulsar mass mp = 1.76 ± 0.06M and a WD mass mc = 1.293 ± 0.025M.


          Not only has the mass of the white dwarf increased to 1.3 solar mass but this may be in the range that is most useful for a Dyson Sphere civilizations. The range of the stable super-Chandrasekhar White Dwarf may have a limit of up to 2.6 mass of the sun! Could this be a way to counter the problems of black holes by turning a White Dwarf into a giant Phase Locked Electron and surfing on the super conducting ring current to any place in the universe?

          Highly magnetized super-Chandrasekhar white dwarfs and their consequences.


          On the fundamental properties of matter.
          By R.C. JENNISON


          What is an electron?
          A new model: the phase-locked cavity.
          by R. C.Jennis0n


          • Michael Fidler December 28, 2017, 22:47

            After thinking about this, how would you get back?
            Maybe this way: Could this be a way to counter the problems of black holes by turning a White Dwarf into a giant Phase Locked Electron and surfing on the super conducting ring current to any place else there is a Highly magnetized super-Chandrasekhar white dwarf with a Dyson Sphere? I’m sure that would be very good for Buisness.* All those Five star Hotels! ;-0

            * Carl Sagans “Contact” Chapter 20 “Grand Central Station”

            And for all you Lunatics: From Sagans Pi in Pi, to a giant Phase Locked Electron White Dwarfs 2160 miles in diameter with a Dyson Spheres 865,000 mile in diameter.

            Think about it, it may be a while before we find that one.

            • Michael Fidler January 3, 2018, 7:15

              Dyson Sphere Musing.

              As you probably know I’v been harping on the White Dwarf + Dyson Sphere issue for a while now, but have started looking at the potential for one nearby. The spacecraft anomalies was were I first started looking, then Planet 9 but in the process came across this image.


              I’m not one to think much of the Nemesis theories, with all the crazy press on the subject, but some of the articles mention white dwarfs as one of the potential candidates. This finally lead me to your article about it and in the remarks:

              James M. Essig July 15, 2010, 18:28
              Hi Folks;

              There are several potential candidates for Nemesis including all of the following: 1) A cooled white dwarf or a black dwarf; 2) A non-magnetically active neutron star or a neutron star whose rF beam does not weep by Earth; 3)A stellar mass range black hole; 4) A large cold brown dwarf; 5) and a Cold Dark Matter body.

              So as you probably guessed, could a civilization have built a Dyson Sphere around a white dwarf that has an orbit around the Sun, assuming that their stealth tech could cover up the IR signature. The more I look a the Nemesis the more it makes sense. The problem with a large 2 sun mass white dwarf is that it would be easy to spot, but if a Dyson Sphere was around it then it might be very difficult to find it. If it has a long period and its orbital eccentricity is not to large, it could exchange comets when close to the sun without disrupting the orbits of the planets in our solar system. Could the gravitational lensing even be seen with a 2000 mile diameter white dwarf covered by a one million mile diameter dyson sphere? Seems the only way to spot it is when it cover up the stars along its orbital path.





              The one million mile diameter Dyson Sphere would have a surface area that is 12,000 times the surface area of the whole earth! A lot of room for all those aliens to hide behind…

    • Michael Fidler January 4, 2018, 20:22

      Astronomers Find Huge Stars More Common Than Previously Thought.

      A star-forming region called the Tarantula Nebula contains more really massive stars than scientists had predicted.

      Within this group, they found more extremely, extremely massive stars than the standard theories say should be there. They found about 30 percent more stars in the upper range of masses, from about 30 to 200 times the mass of our Sun.

      “We found so many of them, it was just astonishing,” says Schneider, who adds that his team initially didn’t even believe their results.


  • Harry R Ray December 21, 2017, 10:36

    Andrew LePage: Habitable planet reality check, PLEASE! My understanding was that a planet with a 30% gas envelope by mass would be a Sub-Neptune, and NOT a Super-Earth! If any H2O(essential for life AS WE KNOW IT)were present, it would MOST LIKELY be in the form of Ice-7. ALSO: According to my calculations, the ONLY atmosphere of this kind where surface pressure WAS equivalent to that at the bottom of Challenger Deep would haveto be composed of PURE HYDROGEN and the mass of the solid core could be NO MORE THAN 0.5 Mearth. Otherwise, the pressure would be MUCH GREATER, and we do NOT know whether ANY KIND OF LIFE AS WE KNOW IT could survive those kind of conditions. If there is any kind of life as we know it on pulsar planets, they would reside DEEP UNDERGROUND on planets who ORIGINALLY had an Earth-like atmosphere and then had that atmosphere STRIPPED AWAY. The kind of planets described above could ONLY host life as we DON’T know it.

  • andy December 21, 2017, 14:36

    My favourite scenario for an exotic habitable zone is planets in close orbits around near-extremal massive black holes heated by blue-shifted cosmic background radiation (presumably in the depths of intergalactic space where everything wouldn’t get heated up by material falling into the black hole). Apparently Miller’s planet in Interstellar would be heated to around 890°C by the background radiation alone, let alone the extra radiation from the accretion disc.

    • ljk December 21, 2017, 17:38

      Of all the places in Interstellar in the Milky Way galaxy alone that they could have gone to search for a new world to colonize, and these supposedly enlightened humans from the future pick horrible worlds around a massive black hole – in another galaxy!

      All that effort and they end up living in O’Neil colonies around Saturn, with no mention if any other such colonies or other worlds in our Sol system were created as well. Even fiction has to make some sense, but Nolan opted for 2001-style abstract mysticism.

      • Brett Bellmore December 24, 2017, 20:46

        It was clearly because that was what was accessible, a wormhole leading straight there having conveniently just shown up. Sending small ships through it was all they could do.

        The O’Neil colonies came about due to data gotten from the black hole allowing them to develop antigravity.

        • ljk December 29, 2017, 12:24

          When it comes to the real colonization of the Sol system and eventually beyond, we are going to have to do it on our own with real science and engineering. We cannot wait for or expect some generous ETI or future humans with time machines et al.

          I am also certain we will find at least a few nice and useful spots among the 400 billion star systems of our Milky Way galaxy.

  • Mark Rayne December 22, 2017, 12:04

    You write that in the novel the cheela live at an accelerated rate as perceived by the human crew and that this is a consequence of coping with a surface gravity 67 billion times stronger than that of Earth. Can you explain this consequence ? (Clocks in a high gravitational field run slow.)

    • Paul Gilster December 22, 2017, 12:56

      Mark, right, I should have gone back to read Forward’s Technical Appendix to the novel, which is somewhere in the office but not immediately accessible. But here is a bit from the prelude of Starquake in which Forward explains what he’s doing:

      “The life processes of the cheela used interactions between the nuclear particles in the bare nuclei that make up the cheela, while life on Earth uses electronic interactions between the electron clouds of the atoms that make up humans. Because nuclear reactions take place a million times faster than electronic reactions, the cheela thought, talked, lived, and died a million times faster than the humans in orbit above them. When Dragon Slayer first took up its position over the East Pole, the cheela were little more than savages and were awed by the laser mapping beams sent down from the middle of the strange star formation floating motionless in their sky. They raised a huge mound temple to worship the new Gods. The humans saw the temple and started sending simple picture messages, one pulse per second. Within less than a day the cheela had developed their technology to the point that they were able to send their first crude, handmade signals to the Gods above them, at 250,000 pulses per second. The humans, finally realizing the immense time difference, worked as rapidly as they could, but nearly a generation went by on the surface of the neutron star before the human laser pulses answered the crude flare signals sent by the cheela below…”

      • stave December 29, 2017, 16:58

        One last example (which we should have thought of at once): The Avatar, 1978. Poul Anderson has his political refugees escaping through the galaxy more or less at random using Tipler machines which had been placed near stars of interest by some ancient civilization, the Others. On one jump (ch 37) they emerge by a pulsar on which lives a species equivalent to Forward’s Cheela who serve as an information source to travelers who stop there and use a communication center created by the Others. Anderson’s and Forward’s descriptions are amazingly similar, though each in their own distinctive voice; Anderson uses his creatures as a very brief, though crucial, episode; and appears to have published first. One wonders if there was any communication between the two, or if it is another example of the Charles Sheffield-Arthur Clark novels about space elevators.

        • Paul Gilster December 29, 2017, 21:47

          Good catch! I had totally forgotten about The Avatar, though I read it when it came out. Thanks!

  • Mark Zambelli December 28, 2017, 12:14

    Paul, et al, I was going to mention my all time favourite author, the late Iain M Banks again but I thought I’d link to our previous thread here… https://www.centauri-dreams.org/?p=30045 back in 2014… well worth another look for not just pulsar environments in fiction.

    Thanks for another years’-worth of outstanding topics Paul and happy hols to all those who contributted to both the articles and discussions.

    • Paul Gilster December 28, 2017, 13:21

      Thank you, Mark, and happy holidays to you and all readers!

  • ljk December 29, 2017, 12:28

    Squishy or Solid? A Neutron Star’s Insides Open to Debate

    Joshua Sokol

    Contributing Writer

    October 30, 2017

    The core of a neutron star is such an extreme environment that physicists can’t agree on what happens inside. But a new space-based experiment — and a few more colliding neutron stars — should reveal whether neutrons themselves break down.


  • ljk January 3, 2018, 17:52

    The Astronomer Jocelyn Bell Burnell Looks Back on Her Cosmic Legacy


    To quote:

    Bell Burnell’s observations during those chilly winter days and nights, signals captured by wires looped across hoary fields, eventually found their way back to the universe that had sent them.

    In the seventies, NASA launched four space probes to explore the outer solar system. Each was outfitted with a map, which used fourteen pulsars to identify our sun’s relative position in the galaxy—the hope being that an alien might one day encounter the probes and find its way to Earth.

    “It was the first time we were actually thinking that something that could be made by humans could leave the solar system,” Keith Gendreau, of NASA’s Neutron Star Interior Composition Explorer mission, said.

    “This kind of crystallized the excitement of the time, of real exploration, of going out there.” Of the possibility of L.G.M. Though neutron stars rotate more slowly as they senesce, the maps ought to be decipherable to intelligent life well into the future. “It would be a little bit of a math problem, but totally solvable,” Gendreau said.

  • stephen January 3, 2018, 22:43

    I had the pleasure of exchanging a few letters with Dr. Forward. I suggested the possibility of white dwarfs and neutron stars having unusual kinds of matter, and he agreed that would be the best reason for sending probes. I cited Procyon B and Sirius B as possible destinations.

  • ljk January 12, 2018, 15:01

    Nature article turns theory of stellar evolution upside-down


    To quote:

    This week, Nature published an article that could challenge the theory of stellar evolution.

    “I think that, over the coming months, stellar astrophysicists will have to redo their calculations,” said Gilles Fontaine, a physics professor at Université de Montréal and one of the authors of the article, titled “A large oxygen-dominated core from the seismic cartography of a pulsating white dwarf.”

    Its lead author is Noemi Giammichele, who completed her doctorate in 2016 under the joint supervision of Fontaine and his colleague Pierre Bergeron, both of whom co-authored the article along with six other researchers. The piece reports on a study of data collected by the Kepler Space Telescope.

    “We were able to map the interior of a pulsating white dwarf star with precision, as if we’d sliced it into cross-sections to study its composition,” said Giammichele, now a post-doctoral fellow at Université de Toulouse, in France. The map showed the star’s vibrations sometimes reach all the way to its centre.