back to article 'Alien megastructure' Tabby's Star: Light is definitely dimming

We might have thought that the long-term dimming of “alien megastructure” star, Tabby's Star, had been put to rest as a calibration error, but boffins now reckon its mysterious dimming can be seen in Kepler data. That, the boffins who checked back four years' worth of observations from the Kepler mission, puts the dimming of …

Page:

  1. Pascal Monett Silver badge

    What about a nebula drifting through ?

    I am absolutely certain scientists have thought about this, but I can't help thinking that a nebula of varying thickness might be able to explain this.

    Of course, I doubt we'd have any way of confirming that. Then again, we know that there is dust between us and the center of the galaxy, and we can still get images in certain wavelengths, so maybe they've already checked and there's no chance of a nebula lurking in that specific region.

    Still, I think a nebula would be possible.

    1. psychonaut

      Re: What about a nebula drifting through ?

      is it maybe an energy saving star? like a compact flourescant bulb. maybe it just takes a while to actually put out any light.

    2. Destroy All Monsters Silver badge
      Alien

      Re: What about a nebula drifting through ?

      For the nebula, you would look at nearby stars (next to the "dimming cat" in space & on the pixel array) to see whether they exhibit similar effects.

      A quick eyeballing of the paper reveals that npo such effects are being observed

      Somebody may be cleaning up the neighborhood ...

      1. Kane
        Alien

        Re: What about a nebula drifting through ?

        "Somebody may be cleaning up the neighborhood ..."

        The Inhibitors are coming...

        1. Graham Marsden
          Coat

          Re: What about a nebula drifting through ?

          If so, they obviously haven't built themselves a Feersum Endjinn!

        2. 0laf

          Re: What about a nebula drifting through ?

          Are the stars turning green over there?

          https://en.wikipedia.org/wiki/Galactic_North

    3. Neil B

      Re: What about a nebula drifting through ?

      Surely a nebula would emit other energies that we could detect.

  2. Scott Broukell

    Are they sure it isn't one of those new fangled energy-saving stars, you know, just never works quite as intended nor as brightly as one of yer normal incandescent ones? Or, maybe it's hooked up to the Smart Energy App of <insert omnipotent deity's> smart phone?

    1. Mark 85
      Alien

      Or maybe someone is playing with the dimmer on the light switch?

  3. Andrew Commons

    A plain old peculiar

    Peculiar variables exist and are documented.

    See for example: http://www.starman.co.uk/variables/types/peculiar/pecstars.htm

    Do we need to get more complicated than this?

    1. Anonymous Coward
      Anonymous Coward

      Re: A plain old peculiar

      Or we could just put it down to "magic" or "aliens".....where's the sense of curiosity?

      Phenomenon that can't be explained by the known facts and theories are the best things ever. An opportunity to do actual science.

    2. Destroy All Monsters Silver badge
      Alien

      Re: A plain old peculiar

      I think it was a "plain old peculiar" somebody might have noticed by now.

      Looks like this kind of approach is classed under "explaining away" or "under-carpetting". This was well explained in Kuhn's The Structure of Scientific Revolutions (which does not quite match how things happen, which is actually rather meta-meta).

      I particularly like this "First of all, the object in question may be a genuine "one off", or it may prove to be a member of a new or existing class of variable.". So it's peculiar because ... it's peculiar. Move along, nothing to see here.

  4. Yesnomaybe

    The star could be exhibiting some kind of long-lived sunspot (OK, OK pedants: "starspot") activity.

    Boring, I know...

    1. phuzz Silver badge

      Generally stars rotate, so unless the sunspot is covering the entire star, we'd expect to see a periodic brightening and dimming, not a prolonged dimming.

      Either way, it's doing something we've not seen before, which makes it interesting.

  5. David Roberts
    Alien

    Light sails?

    Is the fleet already on the way?

    Alternatively, are they having intermittent shortfall in their solar wind power?

  6. Harry the Bastard
    Happy

    cat nap

    obligatory text

  7. Anonymous Coward
    Anonymous Coward

    With us for neighbours

    Who'd blame them?

  8. Milton

    If this continues ...

    ... without good explanation, I do hope someone names it "Pandora's Star".

    1. Peter Gathercole Silver badge

      Re: If this continues ...

      Surely, it must be The Mote in God's Eye.

      The light sail of the Motie ship is just obscuring more of the star as it gets further out, and the rapid change was the planet-based propulsion lasers being turned off.

  9. Anonymous Coward Silver badge
    Alien

    Aliens

    Really low bitrate morse code

  10. Anonymous Coward
    Anonymous Coward

    What is important is what was not said ...

    I think it is important to note the phrase that "no known effect" could explain the observations. The obvious conclussion is that it might be something unknown and new to science. This is excatly the sort of thing that science is built on - find something that cannot be explained by "known science", then come up with a coherent way of explaining it.

    On another note I cannot buy the idea of a Dyson Sphere; they (along with ring worlds) are intrinsically unstable (Larry Niven gave a good explanation in "Ringworld Engineers"). A Dyson Swarm is much more likely; in fact a partially completed swarm that occupies only a fraction of the available orbital slots could explain the observations.

    1. PNGuinn
      Coat

      Re: What is important is what was not said ...

      Or a Henry or Hetty?

      If it's a Dyson Swarm shirley you'd be able to HEAR the buggers from Earth?

      Enquiring minds etc ...

      Mine's the one with ear ear muffs in the pocket

      1. breakfast Silver badge

        Re: What is important is what was not said ...

        They say there is no sound in a vacuum, which may explain why there is so much outside a Dyson...

        1. Anonymous Coward
          Anonymous Coward

          Re: What is important is what was not said ...

          Yeah, a Dyson Sphere in your offices would probably mean the end of your eardrums!

    2. Jez Burns

      Re: What is important is what was not said ...

      I like that thought. It's possible in this scenario that the swarm might not be built by an alien civilisation to harness power for their technology, but built by itself to harness power for itself.

      What do self replicating machines do when they've replicated to the point that exhausted their fuel source? Better pull down the blinds..

  11. sawatts

    Spectrum?

    Any information on whether the star's spectrum has changed along with overall brightness?

  12. Lee D Silver badge

    The Dyson sphere thing just baffles me.

    Why building a huge super-structure around a star, at a distance safe enough to live for the foreseeable future, which is covered on the inside by energy-gathering whatevers, and has living space throughout is some "end game" goal for a civilisation, I can't fathom.

    Hey, look, we spent all our resources and billions upon billions upon billions of tons of raw material - 2.83×10^17 square kilometers of surface area alone, equivalent to millions of planets or thousands of suns worth of material, more than everything available in the solar system around such a star - tied it all into one humungous spherical structure, with a radius something like Earth's distance from the Sun, put all our people inside it, covered it in energy-sucking materials and now we all live in a vast, empty spherical box until the star inside starts acting funny from not being able to radiate as it might normally, for a few hundred thousand years (probably longer than it takes to build the thing) until the star starts acting differently or bulges or something and wipes us out. Not including that we have to somehow keep that centered on the star with propulsion as it's effective average gravity towards teh star inside it would be zero.

    Rather than bugger off, live on other planets around other stars, and use a comparative pittance (still huge amounts, but comparatively nothing) of energy to fuel the mission there in the first place.

    Literally the scale is so vastly infeasible I don't get why it even gets mention in things like this. If you have anywhere near that amount of material, energy and capability, the last thing you're going to want to do is hedge your bets and sit round the campfire for the rest of your existence, even if one side of your house gets nice sunshine without clouds and the other has a perfectly dark view of the night sky.

    Even as purely an energy collector, it's ridiculous. Looking for it as an explanation is even more ridiculous.

    Not to mention, Drake's equation - the chance of observing THAT EXACT MOMENT of someone building this ridiculous structure (rather than it not being built yet, it being already built, or it already having blown to pieces long ago) is basically zero.

    1. You Are Not Free

      If you could actually build a dyson sphere, why at all would you need to?

      1. cray74

        If you could actually build a dyson sphere, why at all would you need to?

        We're at a point where our command of energy allows us to level mountains, shape rivers, light cities, and produce a material abundance unknown earlier in human history. Do we need that power?

        Well, currently, humanity uses machines with engines as powerful as all the mechanical horsepower in one of the 18th Century US colonies to expediently, affordably cross oceans for a frolic in the sun and sand. Sometimes apparently with direct beach delivery.

        So, what about a more advanced civilization? How many terawatts of solar power does it take to boost a starship to a nearby star system? How many petawatts are needed to strip mine Ceres-sized asteroids into millions of giant space habitats for trillions of space dwellers? How much power is needed to manufacture anti-matter for their system-spanning transportation network? That star isn't doing anything useful with most of its core fuel except lighting up the universe, which is sort of futile. Might as well throw some solar panels around it.

        Do they need that power? Could they - or we - have stayed in eco-friendly mud huts and used sustainable biofuels like our ancestors? Sure. But I like my nuclear-powered air conditioner, overpowered car (yes, midlife issues), and the option to fly into St. Maarten to get drunk and go "woooo!" at airplanes passing low enough to decapitate me. That takes lots more power than my ancestors had. Maybe the aliens like their anti-matter fueled personal spaceships and personal O'Neill colonies. That takes more energy than us.

        Or maybe the dimming is something more mundane, like run amok von Neumann constructors who have eaten their makers and are now eating the solar system but really don't need all that power. It'll be a while before we can be sure.

        1. BoldMan

          Or its designed to keep something inside... MorningLightMountain...

          1. NomNomNom

            You only need a Dyson sphere if you can't control your population size. Which is surely an absurd flaw for a highly developed civilisation to have. Unless there's some kind of moral imperative to bring as many sentient beings as possible into existence, there's just no need for an entire Suns worth of output.

            Population capped at 1 million, fusion reactors and everyone plugged into a sim world. You'd only need an area the size of London for your civilisation and could probably set it up in the midst of the void away from dangerous things like stars and planets.

            1. Dave 126 Silver badge

              >You only need a Dyson sphere if you can't control your population size.

              You only need to control your population size if your living habitat is limited.

              As it is today, in developed countries with good healthcare, female education and access to contraception, birth rates are fairly close to death rates. But hey, maybe aliens with extended life spans might rear several hatchlings to maturity over their lifetimes, just for the joy of having the young ones around.

              >Which is surely an absurd flaw for a highly developed civilisation to have. Unless there's some kind of moral imperative to bring as many sentient beings as possible into existence,

              You're second-guessing the ethics of a highly advanced civilisation? It's not unreasonable that a civilisation will see nothing wrong with converting sterile space rock into living space.

            2. allthecoolshortnamesweretaken

              Well, I'd say that we are a highly developed civilisation, and look at all the absurd flaws we have... Being highliy developed and still act irrational isn't mutually exclusive; every single one of us is living proof to that.

              So even a civilisation that has the means to build a Dyson sphere might be doing just that because they are religious nuts. Or lost a bet. Or want to impress their neighbours. Hey, imagine - keeping up with the Joneses on that level, there might be a good story in this.

        2. Anonymous Coward
          Anonymous Coward

          Building a Dyson sphere (or swarm)

          Sure it takes a lot of resources, but if you get to that point, everything is automated. You have a machine that builds machines, and those machines do all the work while you sit back and do whatever a Type II civilization does with all that free time. Maybe the civilization is all machines at that point, and the meatbags died off or left long ago, who knows. You don't care how long it takes, because you are likely immortal, for all practical purposes, when you reach that level of advancement whether you are machine or biological organism.

          I'm not sure why you'd need to put it at Earth distance - it isn't like you will be living on the surface. You might put it at Mercury distance to save material. And you can get that material from your own solar system. Hell, bust up Mercury, Venus and Mars if you need more material. But it could be very thin, basically orbiting solar panels with a way of getting the power to go where it needs to go. Sure it won't last forever, but our sun isn't going to go red giant for 5 billion years, that would allow for a pretty good ROI on the investment to build such a megastructure! And if it is a swarm rather than a sphere, it would be quite feasible to move it to another star if the first one went past its sell by date - though it is probably easier to send your machines ahead to build another one and only move yourself when it is complete.

          As for why you'd need the power of an entire star, well that's not something we can comment on any more than a fly could comment on why humanity needs the amount of power it is using now. Whether they want to run a simulation of the universe or it is to power some unknown piece of tech we don't even think is possible like time travel or teleportion to another galaxy, obviously you'd have some sort of goal in mind for what you'd do with a star's power. It wouldn't matter if their population was 900 trillion or 900,000, if the desire for that much power was something that served their whole race.

      2. Sam Haine

        If you could actually build a Dyson sphere...

        ...you'd build an Eye of Harmony instead.

    2. Kris

      >> Not to mention, Drake's equation - the chance of observing THAT EXACT MOMENT of someone building this ridiculous structure (rather than it not being built yet, it being already built, or it already having blown to pieces long ago) is basically zero

      Depends how many stars you have to observe... And you only need to get lucky once.

      Also, do you not think that a civilisation capable of building such a structure might have a pretty good understanding of the inner workings and life-cycle of the star they are targeting? And do you not think that they might have needs or motived which escape you?

      Just because it's probably not, doesn't mean you/we know anything at this stage.

    3. Pascal Monett Silver badge

      Re: Why building a huge super-structure around a star,

      The idea came from science-fiction. It's not supposed to be feasible, it's supposed to be awesome. It is supposed to mean that the civilization that built it had so much more resources that they decided to do it for kicks. It's supposed to demonstrate just how powerful the civilization that built it is.

      They wouldn't use up all the resources of the system that the star is in, they would use up five or six start systems - because they could. It's the hipster solution to energy gathering.

    4. cray74

      Even as purely an energy collector, it's ridiculous. Looking for it as an explanation is even more ridiculous.

      Taking your assumptions for granted, yes, but you rather overestimated the mass required.

      Hey, look, we spent all our resources and billions upon billions upon billions of tons of raw material - 2.83×10^17 square kilometers of surface area alone, equivalent to millions of planets or thousands of suns worth of material, more than everything available in the solar system around such a star

      The original Dyson sphere posited using many independently orbiting solar collectors, not a true continuous shell. At your suggested area, simple solar cells (mostly aluminum or an oxide with thin film silicon cells) forming panels 1mm thick would require a mass of 8.5x10^20 kilograms - a bit over 1% of Luna's mass. If you pardon the sci-fi reference, this page gives an overview of the classic Dyson "sphere" and some hypothetical variants.

      Obviously, shifting to lighter sub-millimeter foils like solar sails both reduces mass requirements further and gives the individual swarm elements maneuverability. The latter would allow stabilization of the collectors against gravitational influences found elsewhere in the system, like all the planets you didn't need to disassemble.

      (At least not disassembled for the system's power plant. There are a lot of interesting things to do with spare planets once you have the full power of a star handy and a demonstrated ability to mine and process lunar-scale masses into engineered structures.)

      the star inside starts acting funny from not being able to radiate as it might normally,

      The star's going to radiate almost normally, it just added an extra step in the process: first its light warms the solar collection swarm (to about 300K for a low-albedo collector at 1AU from a G2V star), and then the collectors' temperature stabilizes by radiating from its back side. Minus the energy diverted by the solar collection process, the star's power still get into deep space but using a 2AU diameter radiator while the low albedo means you won't reflect too much back at the star.

      The stellar surface might warm up a bit from reflection and the 300K radiator engulfing it, but it's sitting at an advantageous end of the black body curve: radiated power follows the fourth power of temperature. A little bump in surface power will be rapidly reach equilibrium.

    5. Dave 126 Silver badge

      >Literally the scale is so vastly infeasible I don't get why it even gets mention in things like this.

      Because scientists have a sense of humour. The Dyson Sphere concept can be safely used a placeholder, since no one will mistake it as a serious explanation (without extraordinary evidence). 'Tabby's Star' is also refereed to as the 'WTF? Star' (Where's the Flux?), which again signposts the researchers interest. Similarly, the signal that originally lead to the discovery of pulsars was jokingly known as LGM-1 - 'Little Green Men'.

    6. Dave 126 Silver badge

      >Why building a huge super-structure around a star, at a distance safe enough to live for the foreseeable future, which is covered on the inside by energy-gathering whatevers, and has living space throughout is some "end game" goal for a civilisation, I can't fathom.

      The end game is to waste as little available energy as possible, so as to allow the maximum amount of consciousness. As a sci-fi trope, the idea is speculation about factors that limit a population's continual growth.

      Similarly, Iain M Bank's 'Orbitals' concept - a descendant of Niven's 'Ringworlds' but more modest in scale - is based around the idea of providing as much human-habitable area for as little matter as possible. Banks would be the first to admit that he was a fiction writer, so let's ignore the need for impossibly strong materials and radiation-shielding force-fields etc.

    7. Paul Smith

      Drakes equation and statistics

      >>>Not to mention, Drake's equation - the chance of observing THAT EXACT MOMENT of someone building this ridiculous structure (rather than it not being built yet, it being already built, or it already having blown to pieces long ago) is basically zero.

      Yes it's a long shot, but is it exactly a million to one yet?

    8. Captain DaFt

      Taking a different tack with the alien hypothesis.

      Interstellar travel is hard, really hard to do in any organic lifeform's time frame.

      So you've got a stable civilization, no where else can readily get to/communicate with in a usable time frame, aside from an occasional colony ship.

      How do you preserve yourself long term? Stellar engineering.

      Red dwarves last magnitudes longer than larger stars, so you siphon off enough mass to reduce your star to a red dwarf and greatly increasing it's life span.

      Use all that hydrogen you draw off to power things like moving your world inward to the new habitable zone, terraforming, or even creating, new habitable worlds in the new zone, or even build a colony world fleet big enough to carry everybody and their future offspring to another star when this one fails.

      All this is going to take centuries, if not thousands of years, and the machinery involved isn't going to be small, and the orbiting clouds of by-products, raw materials, new construction, whatever, isn't going to be small either.

      (Probably on the scale of when the Mark I sunsucker becomes obsolete, you just start terraforming it, or converting it into a colony ship.)

      But it's probably only just a poorly fusioning star, and not aliens, too bad. :(

    9. Wilseus

      "...we have to somehow keep that centered on the star with propulsion as it's effective average gravity towards teh star inside it would be zero."

      I think I read somewhere that a Dyson sphere would be orbitally stable, unlike a "more, but still not very feasible Larry Niven-style Ringworld."

    10. rdhood

      "Not to mention, Drake's equation - the chance of observing THAT EXACT MOMENT of someone building this ridiculous structure (rather than it not being built yet, it being already built, or it already having blown to pieces long ago) is basically zero."

      Maybe, but observing THIS phenomenon over 4 years, 1480 ly removed, seemed impossible just 20 years ago. IMHO, this aspect of Drake's equation (the odds of seeing something in the sky as it happens being "basically zero") is dead.

    11. Katie Saucey
      Alien

      Spoil sport.

  13. smartypants

    Loose wiring

    I had this problem with one of our lights too. A screwdriver fixed it.

    The heavens take a lot of maintenance. All those bulbs. Some blow from time to time or slowly fade and need replacing. Getting to them is hard without a big ladder.

    God used to be on top of it before Adam and Eve disappointed him by falling into his sneaky talking snake trap. This week he was doing an interview at Revelation TV. It's all go!

  14. IsJustabloke
    Coat

    Stars are mostly big burny things right?

    Don't all burny things get a bit dimmer as they run out of fuel? Not things like gas cookers of course I'm thinking more of your old log fire / bbq type burny thing.

    Perhaps the scientists are trying to hard to avoid a simple explanation. Given the amount of time the light takes to reach us I'd have thought a gradual effect would be exactly what you'd see?

    But I am not an astronomer /astrophysicist but just maybe I'm the "normal guy" who points out the obvious to all the smart guys :D

    1. You Are Not Free

      Re: Stars are mostly big burny things right?

      Depends on the star, some stars get smaller, hotter and therefore brighter as they age.

      Source - http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit2/mainseq.html

    2. cray74

      Re: Stars are mostly big burny things right?

      Don't all burny things get a bit dimmer as they run out of fuel? Not things like gas cookers of course I'm thinking more of your old log fire / bbq type burny thing.

      Stars tend to follow a more complicated route. While they're on the "main sequence" - the longest part of their life when they fuse hydrogen into helium in their core - they gradually get a bit brighter. This is because the core builds up helium, and helium is denser than hydrogen, so the core can be more compact, denser, and hotter, which are conditions to fuse hydrogen faster. It's like a bonfire getting hotter because more of its fuel is burning at once as the fire proceeds.

      At the end of the main sequence, a star runs out of hydrogen fuel in the core. Without new heat to keep the giant gas ball inflated, it begins to collapse. The pressure in the core reaches the point where helium can fuse, and helium fuses more energetically. The star will puff up into a red giant, which is a tumultuous time (millions of years long) but eventually it starts shining in a stable fashion as a red giant - much bigger and brighter than the old main sequence form, though ironically cooler and less massive. The transition to red giant can involve dimming, but it takes a long time to happen.

      This star appears to be in the main sequence, a bright yellow-white F3V star. A sudden change like this is not going to be due to a fuel shortage.

      1. LosD

        Re: Stars are mostly big burny things right?

        Not to mention that 0.3% dimming every year doesn't at all match phases that have time scales of millions of years.

Page:

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon