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Proxima Centauri b: Artificial Illumination as a Technosignature

Our recent look at the possibility of technosignatures at Alpha Centauri is now supplemented with a new study on the detectability of artificial lights on Proxima Centauri b. The planet is in the habitable zone, roughly similar in mass to the Earth, and of course, it orbits the nearest star, making it a world we can hope to learn a great deal more about as new instruments come online. The James Webb Space Telescope is certainly one of these, but the new work also points to LUVOIR (Large UV/Optical/IR Surveyor), a multi-wavelength space-based observatory with possible launch in 2035.

Authors Elisa Tabor (Stanford University) and Avi Loeb (Harvard) point out that a (presumably) tidally locked planet with a permanent nightside would need artificial lighting to support a technological culture. As we saw in Brian Lacki’s presentation at Breakthrough Discuss (see Alpha Centauri and the Search for Technosignatures), coincident epochs for civilizations developing around neighboring stars are highly unlikely, making this the longest of longshots. On the other hand, a civilization arising elsewhere could be detectable through its artifacts on worlds it has chosen to study.

We learn by asking questions and looking at data. In this case, asking how we would detect artificial light on Proxima b involves factoring in the planet’s radius, which is on the order of 1.3 Earth radii (1.3 R) as well as that of Proxima Centauri itself, which is 0.14 that of the Sun (0.14 R). We also know the planet is in an 11 day orbit at 0.05 AU. Other factors influencing its lightcurve would be its albedo and orbital inclination. Tabor and Loeb use recent work on Proxima Centauri c’s inclination (citation below) to ballpark an orbital inclination for the inner world.

Image: Northern Italy at night. City lights are an obvious technosignature, but can we detect them at interstellar distances? Credit: NASA/ESA.

The question then becomes whether soon to be flown technology like the James Webb Space Telescope could detect artificial lights if they were present at Proxima b. The authors detail in this paper their calculation of the lightcurves that would be involved, using two scenarios: Artificial lighting with the same spectrum found in LEDs on Earth, and a narrower spectrum leading to the “same proportion of light as the total artificial illumination on Earth.” The calculations draw on open source software source code called Exoplanet Analytic Reflected Lightcurve (EARL), and likewise deploy the JWST Exposure Time Calculator (ETC) to estimate the feasibility of detection.

What Loeb and Tabor find is that JWST could detect LED lighting “making up 5% of stellar power” with 85 percent confidence — in other words, 5% of the power the planet would receive at its orbital distance from Proxima Centauri. That would mean our space telescope could find a level of illumination from LEDs that is 500 times more powerful than found on Earth.

To detect the current level of artificial illumination (including but not limited to LEDs) on Earth, the spectral band would have to be 103 times narrower. “ In either case,” the authors add, “JWST will thus allow us to narrow down the type of artificial illumination being used.”

All of this demands maximum performance from JWST’s Near InfraRed Spectrograph (NIRSpec). Much depends upon what methods a civilization at Proxima b might use. From the paper:

Proxima b is tidally locked if its orbit has an eccentricity below 0.06, where for reference, the eccentricity of the Earth’s orbit is 0.017 (Ribas et al. 2016). If Proxima b has a permanent day and nightside, the civilization might illuminate the nightside using mirrors launched into orbit or placed at strategic points (Korpela et al. 2015). In that case, the lights shining onto the permanent nightside should be extremely powerful, and thus more likely to be detected with JWST.

That last comment calls to mind Karl Schroeder’s orbital mirrors lighting up brown dwarf planets in his novel Permanence (2002). A snip from the book, referring to a brown dwarf planet named Treya as seen by the protagonist, Rue:

A pinprick of light appeared on the limb of Treya and quickly grew into a brilliant white star. This seemed to move out and away from Treya, which was an illusion caused by Rue’s own motion. Treya’s artificial sun did not move, but stayed at the Lagrange point, bathing an area of the planet eighty kilometers in diameter with daylight. The sun was a sphere of tungsten a kilometer across. It glowed with incandescence from concentrated infrared light, harvested from Erythrion [the brown dwarf] by hundreds of orbiting mirrors. If it were turned into laser power, this energy could reshape Treya’s continents— or launch interstellar cargoes.

A flat line of light appeared on Treya’s horizon. It quickly grew into a disk almost too bright to look at. When Rue squinted at it she could make out white clouds, blue lakes, and the mottled ochre and green of grassland and forests. The light was bright enough to wash away the aurora and even make the stars vanish. Down there, she knew, the skies would be blue.

Back to Proxima b: The LUVOIR instrument should be able to confirm the presence or lack of artificial illumination with greater precision, serving as a follow-up to JWST observations with significantly higher performance. Loeb has previously worked with Manasvi Lingam to show the likelihood of detecting a spectral edge in the reflectance of photovoltaic cells on the planet’s dayside, so in terms of technosignatures, we’re learning what we will be able to identify based on a growing set of scenarios for any civilization there.

The paper is Tabor & Loeb, “Detectability of Artificial Lights from Proxima b,” (preprint). The paper on photovoltaic cells is Loeb & Lingam, “Natural and Artificial Spectral Edges in Exoplanets,” Monthly Notices of the Royal Astronomical Society Vol. 470, Issue 1 (September 2017), L82-L86 (abstract). The work on Proxima c’s orbital inclination is Kervella, Arenou & Schneider, “Orbital inclination and mass of the exoplanet candidate Proxima c,” Astronomy & Astrophysics Vol. 635, L14 (March 2020). Abstract / Full Text.


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  • Michael Fidler May 21, 2021, 9:34

    Unless panspermia only creates species similar to earth like conditions, I would expect we should be looking for mid to far infrared LEDs around red dwarfs. Especially on the dark side of planets where very large infrared eyes would be the norm. Our eyes peak at around 500nm at night, when the rods come out and starlight illuminates the scene. It would be interesting to see if all the brighter starlight in the night sky peaks at this frequency. Maybe even around red dwarfs a species would develop eyes on the deskside of tidally locked planets that see at 500nm.

    • Michael Fidler May 21, 2021, 21:13

      Here is a very interesting possibility, Alpha Centauri A and B would shine very brightly in the night sky of any tidally locked planet around Proxima. This could be for more then 5 days in Proxima b 11 day orbit, but this all depends on the inclination of Proxima b orbit to Alpha Centauri A and B.
      One half of the northern or southern hemisphere on the dark side could also be illuminated by the two stars continuously if the inclination was right. This could be very significant if these nearby stars are as bright or brighter then the full moon on earth. Just as many species of animals are nocturnal on earth this could make any evolution of night vision on Proxima b sensitive to the yellow-orange or amber part of the spectrum. Should we be looking for low pressure sodium lamps since they are less light polluting of the night sky and they match the light coming from Alpha Centauri A and B better then high pressure sodium lamps?



      • Martin May 22, 2021, 16:52

        Proxima is a long way from the A-B pair (about 12,500 AU) as I recall. The combined light from A and B is about twice that of the sun. The full moon is 398,110 times dimmer than the sun. Putting it all together: 398,110 X 2 X 1/12500^2. About 0.005 of a full moon.
        It’s a neat idea for red dwarf planets in somewhat more closely separated multiple star systems though.

        • Michael Fidler May 22, 2021, 21:53

          Thank you for the reply, Matin, but how much brighter would it be then our starlit moonless night sky?

        • Michael Fidler May 23, 2021, 0:04

          Or at what magnitude would Alpha Centauri A and B be in Proxima b’s night sky?

          • Martin May 25, 2021, 18:17

            “how much brighter would it be then our starlit moonless night sky?”
            That’s a harder question, because I don’t know offhand how bright the (moonless) night sky is, and what contributes to it (starlight, multiple light scattering events from the dayside, light reflected from interplanetary dust all come to mind offhand)
            ” what magnitude would Alpha Centauri A and B be in Proxima b’s night sky?”
            That’s easier. 0.005 corresponds to a magnitude difference of 5.73. Since the full moon is magnitude -12.7 that gives a magnitude of -6.97 for the AB pair. That’s pretty bright! Sirius, the brightest star in Earth’s sky is -1.46. That means the AB pair is about 160 times brighter than the brightest star in our night sky. (I hate magnitude. I have no intuitive feel for what it means, so I wrote a little excel spreadsheet to let me convert from brightness difference to magnitude difference, and vice versa.)
            I have work to do, but I’ll see what I can find about the brightness of the night sky.

            • Martin May 27, 2021, 19:03

              “how much brighter would it be then our starlit moonless night sky?”
              Okay, here’s what I have:
              1. I found a Phill Plait article in which he says that if you combine the magnitudes of the 6000 visible stars it gives you a magnitude of -5. On the surface of course you wouldn’t see all of them (the planet’s in the way!) so I’ll make that dimmer by a factor of 2, giving a magnitude of -4.25. Since the AB pair is magnitude -6.97, that means the AB pair is 12 times brighter than all the stars.
              2. If you just Google “how bright is the night sky” it informs you that contributions to the night sky brightness are 65% airglow, 27% Zodiacal light and 7% scattered starlight. There’s Wikipedia articles on airglow (its from photo chemical reactions in the upper atmosphere) and Zodiacal light (it’s from scattered light by interplanetary dust). If you assume that Proxima night is like Earth night, only with AB added and assign 100 arbitrary units to Earth night then Proxima B night would be 65 airglow, 27 Zodiacal light, 7 scattered starlight and 7 X 12 = 84 from AB.

    • Jean Schneider May 22, 2021, 1:23

      The idea of very large eyes was already discussed by Huygens in his Cosmotheoros, for species living in Jupiter where the faintness of the solar light must be compensated by large pupills.

  • Ivar Brouwer May 21, 2021, 10:56

    All that assuming the intelligence there (if they exist) has evolved to use light, while they might have originated on the dark side and use minimal light, touch, smell, plugged in telepathy or other senses. The hypothesis is very much made with a human like intelligence in mind.
    As per usual Loeb asks interesting questions that are more SciFi then science.

  • Gary Wilson May 21, 2021, 15:26

    A little bit of an aside to the main theme of this post but I’m encouraged that we have a project such as Starshot Breakthrough underway. We may see incremental progress towards the goals of the project in that we may be able to produce some type of probe that is heavier and able to achieve a lesser speed but with more capability to send back information. It seems to me that a goal along the path towards Starshot’s ultimate parameters may be much more likely to be reached. If we could get probes to Proxima Centauri within 100 years of the launch date with enough capability intact to send information back, that may be a more realistic and achievable goal for humanity. The point is we may be far more likely to achieve these goals in a path towards much more sophisticated set of machines. Of course we can’t predict the path of future progress in various fields so we may end up seeing the older probes being caught and passed during the voyage by more capable, newer probes. That would be wonderful indeed as it would offer a form of redundancy in getting information back. I have seen posts on other blogs which indicate a firm belief that such a project cannot succeed for a variety of reasons but I remain convinced it can and eventually will succeed.

  • Alex Tolley May 21, 2021, 15:31

    While interesting to know the illumination level needed to be detectable, one has to ask why a civilization would create such an intense illumination that is largely lost to the sky.

    5% of stellar output reaching Proxima b is a lot of energy. Why squander it on illumination? Nightside is likely to be cold, so thermal control seems like the priority. So structures might be more like those within the Arctic circle on Earth – highly insulated with low levels of external illumination.

    Apart from city centers, we are increasingly becoming aware of the damage night illumination is to the lives of animals. We are slowly coming to understand that night illumination needs to be as unobtrusive as possible. An advanced civilization that has determined to populate the dark side of its planet may decide to use technologies that don’t interfere with wildlife – autonomous vehicles that don’t need light, and underground/enclosed transport systems, etc. If growing crops is determined to be a gamechanger, perhaps growing them in enclosed farms with opaque walls is the best solution, rather than illuminating the landscape with light from whatever source.

    One has to imagine that a permanently cold, dark hemisphere will not have photosynthetic autotrophs powering a food chain. This means that there won’t be soils, just glacial moraines. Any animals will be migratory, or sea dwellers that reproduce and hide from sea predators at the edge of continents. Illuminating such a landscape to “terraform” it to conditions where life exists on the world would be a massive endeavor. It would be far more efficient to create highly intensive food production systems in controlled environments, as well as any recreational “natural” spaces. All indoors seems most likely.

    One advantage from our perspective is that lack of vegetation means that we will not confuse wildfires for artificial illumination, although active volcanoes might be confusing.

    If the ETI population normally lives on the star facing hemisphere, then I could see mirrors being used to extend the edges of their inhabited areas towards to twighlight zone and beyond. The orbiting mirrors might be relatively few, to increase illumination allowing vegetation and habitation to extend into more dimly lit regions where transporting soils and vegetation is a smaller scale operation. In principle, this could eventually extend all the way into the dark hemisphere, but, as on Earth, the economic costs of outdoor illumination will result in expansion via thermally insulated structures with internal illumination.

    For a spacefaring civilization, I could see beaming energy to power spaceships and outposts in the outer system making sense. Perhaps looking for these energy beams might be easier? Certainly another long shot that might be easier to detect with a small space telescope.

  • torque_xtr May 21, 2021, 17:19

    I doubt that red dwarf planet dwellers would use the same LEDs that we use. While it is reasonable for them to have some sensitivity to UV-Vis, they will hardly use it for lighting. To them, any significant increase of illumination shortwards of 600-700 nm would be associated with an instinctive urge to burrow underground as fast as they can because a flare is coming. To their eyes adapted to twice less energetic range, our white light LEDs would be worse than arclight for us, and even sodium lamps would look like a mercury-lamp sterilizer. This raises another problem – it would be more difficult to distinguish between artificial lights and chains of volcanoes on a tidally-heated world, because lava emits much more in NIR than in visible light. Again, to the eyes of native inhabitants, a lava flow would look as incadescent as a tungsten halide lamp to us.

    That is, of course, if they have eyes and rely on optical imaging not significantly less than we do.

  • Dale May 21, 2021, 19:15

    Whilst I agree that their habitats would have low levels of external illumination,they would have to get from A to B, presumably using well lit roads!

    • Alex Tolley May 21, 2021, 22:36

      Consider that roads were no lit at all outside of cities until the industrial revolution. Coaches would bring along lamps to aid navigation, although I have never seen that used in US Western movies (did the coaches always travel only by day in the US?). With manual navigation of autos, the autos brought along their illumination for drivers, and only high thoroughfare roads had their own lighting. City streets with pedestrian sidewalks also used public lighting. As we transition to autonomous vehicles that can rely on other senses – IR, radar, only low-intensity navigation lights need to be used to indicate the presence of the vehicle, like ships and aircraft.

      • Robert May 24, 2021, 9:33

        From “The Stagecoach in 1860s The Passenger Experience” – by Jay W. Sharp

        “They travelled relentlessly, day and night, with no more than brief moments at way stations for often poor food and no rest. ”

        Read more: https://www.desertusa.com/desert-activity/stagecoach-service.html#ixzz6vmyeRlT6

        • Alex Tolley May 24, 2021, 14:20

          Robert, thanks for the link. So night travel, but no indication of coach lights to illuminate the way – probably inadvisable in Indian country! Director Ford’s Westerns are gorgeous but inaccurate (I’m shocked, shocked!) [Night scenes in classic westerns were filmed during the day and the light level manipulated in some way – camera exposure or developing, IDK which.]

          • Robert May 25, 2021, 16:31

            Old photos and images show lanterns on the sides near the front on many coaches. I would not equate them to headlights per se but they probably helped avoid disasters at night. Also, drivers likely knew the routes well enough and many nights there would have been adequate moonlight. This link is about coach travel at night and includes some images of Remington paintings and a Wells Fargo coach.


            • Alex Tolley May 26, 2021, 12:01

              Thank you for that link. So it appears that the US ran its coaches at night with lamps, just as they were run in Britain and Europe. I presume these lamps were not permanently fixed as the [Wells Fargo?] coach in Old Town Sacramento doesn’t have the lamps and I do not recall any fixtures to hold them.

              Another reason to remember that Hollywood is fiction! I will make a mental note to look out for any coach lamps in my movie collection depicting coach journeys in the US.

    • Ivar Brouwer May 22, 2021, 7:14

      These Guys Will have GPS too, no need for looking at roads, or other ways of transportation: everything will be automated.

      • Dale May 22, 2021, 19:27

        Thanks for the reply Alex and Ivar.We may presume that they have autonomous vehicles which don’t require additional roadside lighting but maybe they just like to use it as a form of nostalgia from a bygone era.Much like out reversion from CDs to cassette and vinyl.I had thought of the GPS question myself,Ivar.Would we be able to detect satellites around Proxima Centauri b?

  • Henry Cordova May 21, 2021, 23:21

    I would hope that an advanced extraterrestrial intelligence would be able to design its streetlights so they illuminated the ground, not the celestial sphere. Maybe we don’t do that, but then we are neither advanced, extraterrestrial or intelligent.

    Then again, maybe Proxima’s inhabitants live underground, or under water, or have eyes that can see by starlight, or maybe they don’t have eyes at all. Or maybe they have an astronomers’ lobby agitating successfully against light pollution.

  • Jean Schneider May 22, 2021, 1:33

    The idea to search for city lights was also developped in https://arxiv.org/abs/1712.07479
    In addition, on the dark side of the planet one can search for the heat produced by any industrial activity.

  • Robin Datta May 22, 2021, 2:13

    If I were a betting man, seing that Proxima b is the only available option, I too might place a few mental bets there, but not with much enthusiasm. Heavily colored by my bias towards the kind of life that I have come to view as “natural” on this planet, I would be laboring under the presumption that any other kind of life is unlikely.

    However my “lizard brain” might still be hoping for a pleasant surprise.

  • AlexTru May 22, 2021, 3:27

    Homocentric sci-fi speculations.
    (Ignoring ridiculous hypothesis about 5% spent for lighting, and LED lighting)…
    Probability that Proxima’s ETI are using LED technology exactly same moment as we gazing at them , is multiple orders lower than probability of intelligent life existence in proximity of the Red dwarf…

  • Donald May 22, 2021, 8:17

    I would just like to correct something you said about the launch date of LUVOIR. There is no possibility it will launch in 2035. Two architectures were studied with reports generated for each: an 8 meter off axis design with a targeted launch date in early 2039 and a larger 15 meter architecture with a launch date in late 2039. Now, we know these large projects usually get delayed and these reports were released before Covid hit and JWST and other space missions got delayed so you can reasonably push these optimistic launch dates into the 2040’s now, but even if you want to continue to take the reports at face value, which seems silly given what’s happened because of Covid and the history of large astrophysical science observatories, there is still no possibility of LUVOIR launching in 2035.

    • Paul Gilster May 22, 2021, 12:03

      I’ll have to agree with you after digging a bit more into this. Even 2039 seems too optimistic.

  • Alex Tolley May 22, 2021, 10:51

    One would think that the probable separation of civilizations in both space and time would extinguish what I call the Star Trek galaxy POV: that there are many civilizations that with amazing synchronicity just happen to be physically similar to us in form and culture, but fairly close in technological capability. (This is not purely a ST problem and applies to much written SF and commercial video production, which is valid if SciFi is about the human condition, not science.) ST has a resemblance to the “Age of Exploration”, and even to the following period of colonization. The idea of a “Galactic Club” of communicating civilizations is behind most of earlier SETI investigations, although if they are very long-lived and ancient, one questions why radio is the preferred communications medium. IMO, the only probably way to get synchrony between civilizations is if the stellar civilizations are due to colonization efforts and therefore the worlds are likely fairly close and the cultures of comparable age and similarity to want to communicate just as colonies did (and do) in our history. We may detect some leakage if the source is not too distant.

    I am very much in the camp of those who think we should look for artifacts that can survive for millions of years after the demise of civilization – such as satellites, and hardware/structures on a dead worldlet. These may be harder to locate, but just like the artifacts of early- and pre-civilization humans that last for thousands of years and communicate to moderns through deep time, such ETI artifacts might last for millions of years.

    In the case of Loeb’s paper, I find it extremely hard to believe that there is a civilization of some sort of technological age as ours, with a recognizable culture (city builders, lighting their cities as we do, perhaps driving vehicles on well-lit highways, etc.) conveniently located in the nearest star system which just happens to have the properties that just might, under some circumstances, be detectable by the latest space telescope when it launches.

    I do wonder whether papers such as Loeb’s are trial balloons that will be accompanied by a funding request, e.g. time on a telescope to test the idea. Is this the astronomical equivalent of an “elevator pitch”?

    • David May 22, 2021, 19:08

      Alex ,
      You might be right, I have seen a colleague do this

    • Andrei May 25, 2021, 21:04

      Thank you for your post Alex, it spare me the trouble to writing a similar long reply. My view remain the same that our first proof of intelligence elsewhere indeed is more likely to be an artifact – with a broadcast message on second place, made with a technology we do not expect or even able to use yet.
      Lets hope other intelligent species is not as shortsighted and expect everyone to be like them. Else there might have been a race of intelligent (but blind) moles in another star system, who write their own proposals on interstellar exploration – in braille writing. On how to use their version of project starshot to send seismometers to nearby planets in an attempt to find which planets that got a civ with a subterranean subway network.

  • Triffin May 22, 2021, 14:53

    “We should look for artifacts”

    A simple search for “anomalous objects” on the Moon or Mars
    returns all sorts of hits with links to the photo libraries of the
    various orbting mapping/survey missions .. I would certainly
    hoping we are using AI search algos on the photographic data
    already in hand ..

    I’ve yet to see a refutation of the so called triple towers on Mars ..


    • Dale May 22, 2021, 19:36

      I think Paracelsus c is also worth looking at.Could be a natural rock formation but I’d like to see Elon Musk send a rover down there to have a closer look.

      • tesh May 25, 2021, 2:57

        Sorry if this has been discussed or done but has anyone modelled parameters (below) to get at how long these “structures” have been there and how they might look if further exposed?
        – dust/rhinolith accumulation (expected vs actual)
        – “weathering” (if applicable), to get at the potential material it is
        made of
        – local impacts size/frequency of meteorites relative to general

  • Gary Wilson May 22, 2021, 15:20

    As far as artifacts go it will be almost impossible to even estimate how long it may be for us to find them. Our “radius of investigation” as of now is very tiny indeed. We can get very brief glimpses of various places in our own solar system. The farther away each body is, the less frequent are our observation points. We can fairly systematically observe the Moon, Mars, and a few of the larger asteroids so far. Other stellar systems remain far beyond our reach. Unless the UAP’s that are now becoming more acceptable to discuss in the scientific mainstream are actual physical artifacts (some aspects of their observed properties seem to argue against that) then it seems to me we will wait a very long time indeed to find physical evidence of ETs. That’s not to say we shouldn’t look, but the search time will probably be in centuries or millennia. I think we are definitely going to have to think far outside the box to even develop realistic theories about what the UAPs are. They almost certainly don’t contain organic beings. Accelerations of up to thousands of gravities have been recorded. It seems likely that if they are artificial they are robotic. Our capabilities are laughable in comparison. I am completely confused as to what their source is but it’s an incredible opportunity to widen our perspectives.

  • Michael Lorrey May 22, 2021, 18:25

    If Proxima b has significant liquid water on its surface it is very unlikely to be tidally locked unless its axis of rotation is oriented toward its primary rather than perpendicular as most planets are. Particularly if it has a moon of any significance. Furthermore, it is close enough to its primary to experience tidally influenced seismic heating which would induce it to maintain an active volcanic system and liquid mantle/outer core which would cause the core to spin independently of the mantle and crust, thus inducing a geomagnetic field system providing some measure of protection against flares.
    Estimates of b’s size and mass seem to still be rather fraught with assumptions and wide ranges of error. Your point about eccentricity, which would be a result of influence from Prox c also mitigates against tidal locking.

  • andy May 23, 2021, 6:52

    At this point, I’m filing anything with Loeb’s involvement in the same place I would file anything by Wickramasinghe and the Journal of Cosmology folks: he seems to have come down with a severe case of ʻOumuamua Derangement Syndrome, and I’m not trusting anything he says which hasn’t been backed up by other independent studies. He’s repeatedly putting out extremely sloppy papers which outright ignore existing literature (see for example the response by Desch et al. to his recent claim that the Chicxulub impactor was a comet) in areas of large public interest and going to the media at the first opportunity.

  • Patient Observer May 23, 2021, 21:11

    1 – Grasping at straws
    2 – A need for academic attention
    3 – Sniffing out funding opportunities
    No science, no plausibility, just “look at me!”

    The only thing astronomical about the premise of nighttime illumination being detected across light-years is the astronomical number of assumptions each with an infinitesimal probability. It would not even make a half-baked SciFi premise.

  • Mike Serfas May 24, 2021, 9:15

    It’s hard to deny the absurdity of the premise from our perspective. Still, we should bear in mind that aliens might develop under very different circumstances. For example, the dark side of a tidally locked planet might be habitable, with reliance on “anti-solar cells” – emission of thermal energy to the night sky – for power and (anti-)photosynthesis. A pipe system that can circulate fluid from the uninhabitable day side could produce a lot of power – essentially, a concentrated solar power plant, with fewer if any mirrors needed – and then release it on the night side. This would be hard to tell from thermal energy, but if anti-solar technology is moderately well developed (more than a mere cooling tower, but not such an efficient combination of semiconductor options as to become indistinguishable from noise), the photons might be emitted in narrow frequency bands that would stand out.

    Alternatively, consider how evolution might progress without a Moon. With no moonlight at night, evolution would have to choose between gigantic eyes to see by starlight, or simply adapting to daylight. That means eyes with no equivalent of rods – permanent night blindness. Such organisms could plausibly resort to making the nightside of a rotating planet look like day, to extend their activities.

    Do I expect any of this on Alpha Centauri planets? Not at all! But those planets are our nearest neighbor, a beacon to our curiosity, a place we can look up to and wonder about like the Moon was a few centuries ago. And so clearly we should want to know what the night side looks like in as much detail as we can, even if all we find is aurorae or fountains of burning sulfur. If JWST makes it into space, it should point at that system a good long time, and considering the money that went into that science project, people had better be analyzing every scrap of the data coming back in every possible way they can – leaving no possibility, however absurd, unexamined.

  • ljk May 24, 2021, 13:58

    Astrobiologist Jason Wright makes some important distinctions between SETI and Ufology:


    • Alex Tolley May 24, 2021, 16:18

      Good to read that Wright is making such a statement. He confirms some important points and I like his observation that such UAP/UFOs are always on the edge of detection despite the increasing capabilities of our detectors.

    • Gary Wilson May 25, 2021, 17:44

      It seems logical that Dr. Wright would take that point of view. UFO or UAP investigations are not SETI really and require different skill sets as he points out. His comment about being suspicious that so many of the sightings are US based (at least I think that’s what he’s trying to point out) isn’t really valid. Much of the international news is US dominated, but I have seen many, many UFO sightings reported from all over the world. The release of some captured sightings by US military pilots is just a drop in the overall bucket of sightings over many decades. Systematic analysis of all sightings is required in a non-biased way. Surely the time for automatically assuming all sightings are mistakes or outright fraud is over? Many are likely natural phenomena, some are fraudulent but there seem to be many examples of something real we don’t understand. People didn’t know what sprites were a few decades ago and would probably have scoffed at the idea. I admire Dr. Wright’s refusal to get embroiled in something outside of his own field.

  • Picaworth October 30, 2021, 11:52

    This raises an interesting hypothetical question. If the nightside of Proxima b is illuminated by artificial light, could we detect it with HST s successor, the James Webb Space Telescope (JWST), scheduled for launch this year? Since JWST is bigger and more sensitive than HST, it would allow us to peer farther into space and extend the search for artificial lights from the Kuiper belt to habitable exoplanets like Proxima b. I explored this question in a new paper with an undergraduate student from Stanford University, Elisa Tabor.