Did the Kepler space telescope discover alien megastructures?
[UPDATE5: In SETI: No Signal Detected from KIC 8462852, Paul Gilster quotes Seth Shostak: “The history of astronomy tells us that every time we thought we had found a phenomenon due to the activities of extraterrestrials, we were wrong. But although it’s quite likely that this star’s strange behavior is due to nature, not aliens, it’s only prudent to check such things out.” Well said, and I do hope SETI succeeds in my lifetime. –Jim]
By Jim Galasyn
23 October 2015
(Desdemona Despair) – The last couple of weeks have seen a flurry of speculation about an observation made by the Kepler space observatory: is it evidence of alien megastructures, like a “Dyson swarm”? The Kepler satellite looks for extrasolar planets (“exoplanets”) circling distant stars in a small square of sky near the northern constellations of Cygnus, Draco, and Lyra. Launched in 2009, the Kepler mission has been immensely successful, discovering more than 1,000 exoplanets in about 440 stellar systems by the year 2015. Kepler is an orbiting telescope that looks for the slight dimming of a star’s light as a planet passes in front of the stellar disk. When a planet transits its parent star, the light from the star dims, usually in a symmetrical pattern.
How then to explain these asymmetrical light curves from the star KIC 8462852?
Tabetha Boyajian and colleagues have examined the unusual photon flux data from KIC 8462852 (“Tabby’s star”) in various ways, and they conclude:
The scenario most consistent with the data in hand is the passage of a family of exocomet fragments, all of which are associated with a single previous breakup event. [“Planet Hunters X. KIC 8462852 – Where’s the Flux?”]
It’s an unsatisfying explanation for a number of reasons that they discuss in their paper. Naturally, people have started wondering if we’re looking at the long-sought evidence of extraterrestrial intelligence: the shadows of giant, irregular structures created by an ancient, spacefaring civilization. I’m as fascinated with SETI as the next geek, but claims of evidence for extraterrestrials must be viewed with great skepticism. The photon flux data captured by Kepler appear to be unlike anything seen before, but really, it would be incredibly lucky for one of the very first probes sent by humans on a planet-finding mission to discover evidence of an alien civilization. So a closer look for natural causes is necessary.
After obsessing over the graphs in the Boyajian paper for a while, I ran across a paper posted by commenter Michael at Centauri Dreams: “Measurement of spin-orbit misalignment and nodal precession for the planet around pre-main-sequence star PTFO 8-8695 from gravity darkening” (Barnes, et al., 2013) [pdf]. This paper goes a long way toward explaining the anomalous light curves of KIC 8462852. [But see UPDATE2 below.]
The idea is that some stars don’t have uniformly bright disks. Some stars spin at a high rate, giving them an oblate spheroidal shape and causing an effect called “gravity darkening”.
When a star is oblate, it has a larger radius at its equator than it does at its poles. As a result, the poles have a higher surface gravity, and thus higher temperature and brightness. Thus, the poles are “gravity brightened”, and the equator “gravity darkened”.[1] The star becomes oblate (and hence gravity darkening occurs) because the centrifugal force resulting from rotation creates additional outward pressure on the star. [Gravity darkening]
There are four discrete events in the Kepler data for KIC 8462852, and planetary transits across a gravity-darkened disk are plausible causes for all of them. The first event occurs at Kepler day 792 into the mission (D800). It’s similar to the usual light curve for a transiting planet, but it’s asymmetrical. Boyajian says of the first event:
A fairly generic prediction of transits of comet-like bodies may be that their light-curves show signs of their tails. The light-curve expected for a typical event then has a relatively fast ingress as the head of the comet passes in front of the star, but a slower egress as the tail passes (e.g. Lecavelier Des Etangs, et al., 1999; Rappaport, et al., 2012). However, the D800 event [what I’m calling day 792 –Jim] shows the opposite (see panel ‘c’ in Figure 1). Possible resolutions of this issue are that the D800 comet fragment received a large kick with an orientation that sheared it out in such a way to form a “forward tail”. Such forward comet tails produced by the fragments being kicked toward the star have been studied in the literature, but require the tail to be large enough to overcome the effects of radiation pressure (Sanchis-Ojeda, et al., 2015). Alternatively, this event could be comprised of two dips superimposed to have the appearance of a forward tail. While several issues remain to be explored, of the scenarios considered we conclude that a cometary origin seems most consistent with the data to hand.
But a similar asymmetrical light curve can be produced by a transit across a gravity-darkened disk:
The third event at day 1540 is symmetrical but features lobes on either side of the minimum.
My first thought was that this is clearly a ring system, with a “Cassini division” on either side of the central planet. But a similar curve results from a transit across a symmetrically brightened disk:
The second and fourth events at day 1520 and day 1570 have a qualitatively similar shape but different magnitude. I’ve applied an arbitrary horizontal (time-axis) scaling to size the day 1570 event roughly with the day 1520 event.
Although they have interesting high-frequency details, in general both curves follow the characteristic shape of a transit across a brightened pole.
The two events appear to be transits of two planets. The first planet is large, occluding 20% of the star’s disk. The second planet is much smaller, occluding just 8% of the stellar disk. Because the second event has shorter duration, the smaller planet is moving faster and therefore is orbiting closer to the star. The high-frequency variations aren’t predicted in the Barnes paper. I speculate that the gravity darkening around the star’s equator may be banded, like Jupiter’s atmosphere. If this idea holds up, planetary transits could be a valuable tool for inferring stellar surface dynamics. [But see UPDATE below.] Together, the three transits might look something like this:
As noted in Wright, et al. (2015), there are other interesting events in the KIC 8462852 data:
The event on the left, at day 262, is an ordinary transit. On the right, at day 1206, is another transit across a symmetrically brightened disk. Both are very small planets, relative to the planet in the day 1520 event. Did Kepler discover evidence of an extraterrestrial civilization? Before we invoke aliens, we should consider the plausible natural explanation provided by Barnes: “An oblique transit path across a gravity-darkened, oblate star leads to the long transit duration and asymmetric lightcurve evident in the photometric data.” UPDATE: A quick literature search produced another interesting paper on stellar system PTFO 8-8695, “Revisiting a gravity-darkened and precessing planetary system PTFO 8-8695: spin-orbit non-synchronous case” (Kamiaka, et al., 2015)[pdf]. Here are three possible transits that could fit the observed data:
UPDATE3: Here are the interpolated curves from the Kamiaka paper, compared with the observed data from KIC 8462852.
I had thought that bands in the stellar disk would be necessary to account for the high-frequency details of the light curve, but it seems that they’re not.
UPDATE2: One of the anonymice points to a compelling new paper, “Tests of the planetary hypothesis for PTFO 8-8695b” (Yu, et al., 2015)[pdf] that disconfirms the Barnes paper: “All these observations cast doubt on the planetary hypothesis, and suggest instead that the fading events represent starspots, eclipses by circumstellar dust, or occultations of an accretion hotspot.”
The Yu paper finds that the hypothetical curve fits computed by Barnes, et al., don’t fit the long-term observations of the PTFO 8-8695 system. This is an entirely reasonable result. I don’t think this weakens the case for KIC 8462852, since these wacky curves are present in the observed data.
The other objection to the gravity-darkening hypothesis is that the two big KIC 8462852 events (20% dimming and 8% dimming) are far too large to be caused by planets; a comparable Jupiter transit would dim the sun by about 1%. This is a fair point, but it doesn’t significantly weaken the case for transits of some large object(s) across a gravity-darkened disk. Also, it’s worth noting that one of the solutions presented by Kamiaka (the blue trace in the above graphs) predicts a dimming of 30% for a planet in the 3-4 Jupiter mass range.
[UPDATE4] I emailed Professor Barnes for his thoughts on KIC 8462852, and here’s his reply:
Indeed, the individual transit events in the KIC 8462852 lightcurve definitely show the signature of a misaligned object transiting a gravity-darkened stellar disk. Even if PTFO 8-8695b looks like it probably isn’t a planet, we have seen this kind of gravity-darkening signature at Kepler-13b, for instance. But WHAT might be transiting at such odd cadences and with such differing durations is far less clear. The Kepler-13 gravity-darkened transit signature paper can be found here.
Thank you, Professor Barnes!
Aliens are just a Jesus story for the more wimpy of the secular. We can't accept that we are the most intelligent beings that have ever lived, because we are still hopelessly stupid. I love how Scientists say that things must be proven, and yet speculate constantly about intelligent life on other planets. Even with human level intelligence, we are able to realize the futility of existence. A super intelligence could only exist as a non-biological life form.
None of what you said is true. You don't understand enough to realize aspects of existence, certainly not enough to judge futility simply from scale. The way you use the word secular implies that you don't understand what it means as well… You can be religious and still secular. How are aliens a Jesus Story? No one is using made up teachings by these aliens to justify behavior and belief… scientists are just cracking open the window to what can be found and understood in our universe. No one in the scientific community takes a hypothesis (much like the Jesus hypothesis) and supplies no supporting evidence AND demands it be universally accepted… That's the monotheist school of thought…
Wouldn't it be unusual for the orbit of the planet to be anything other than generally perpendicular to the spin axis of the star? And if the spin axis of the star is roughly fixed in space, I am not understanding how this can occur.
Thanks for this! As much as I'd love to think it was aliens, I much prefer a natural explanation – and I'm totally intrigued by the idea of a gravity dimmed star! Also, my wife says you get a cookie, for being so awesome with your academic rigor. ^_^
@Jeff, as a rule this is the case, but iirc something like 33% of "hot Jupiters" are in highly inclined orbits. Also, keep in mind that many stars have a high obliquity, which is why the diagrams I copied from the Barnes paper have the south pole of the star rotated toward us.
Another angle that I didn't mention in the blog post is precession: both the star and the planetary orbits may be precessing, which makes predicting transits more complex.
Anonymous – none of your comments make any sense, which I'll take as proof that some humans are still quite stupid.
a) Aliens are just a Jesus story for the more wimpy of the secular.
Totally nonsensical, convoluted and irrational.
b) We can't accept that we are the most intelligent beings that have ever lived, because we are still hopelessly stupid.
Broad brush claims are rarely accurate. I'll agree with the stupid part of you know who.
c) I love how Scientists say that things must be proven, and yet speculate constantly about intelligent life on other planets.
This hints at your religious indoctrination (brainwashing) also hinted at in sentence 1. Scientists are supposed to speculate, investigate, experiment and prove out hypothesis and theories. The computer you're writing on is an example of that effort.
Moreover, there is no valid reason not to speculate about intelligent life – unless you're one of the indoctrinated fools that think we're so special that we must be the only ones (nobody knows that and therefore, it needs to be investigated, starting with speculation and then investigation).
d) Even with human level intelligence, we are able to realize the futility of existence.
A statement which has zero relationship (off-topic) to the rest of your screed (and it contradicts sentence b. Might want to polish up on your communication skills (obviously).
d) A super intelligence could only exist as a non-biological life form.
Once again, you prove sentence b – you're among the most hopelessly stupid of the species. You know that a super intelligence has to be non-biological? Based on what facts or evidence?
Oh, that's right, more speculation and useless conjecture from a couch expert.
Your total failure to realize the significance of science, the scientific method, the search for other signs of life and the importance of this effort is appalling. You never did make a legitimate comment on the article either.
I can only surmise based upon your inane commentary that you'd rather humans gave up altogether and most probably wait for the magical appearance of the invisible Sky God to save humanity from itself. Or perhaps you would just prefer we continue on the path of self-destruction and denial of knowledge and research.
In any case, I'm very glad that people like you are in an increasingly smaller and smaller minority these days since a return to the Dark Ages would definitely not be in everyone's best interest.
"I can only surmise based upon your inane commentary that you'd rather humans gave up altogether and most probably wait for the magical appearance of the invisible Sky God to save humanity from itself."
I'm a radical Atheist. Unlike most Atheist's I have no romantic notions about the earth or human existence. There is absolutely no reason humans need to exist, or any other biological life for that matter. I highly recommend you read the book Better Never to Have Been, The Harm of Coming Into Existence, by David Benatar. And before you even start with the, "why don't you just kill yourself" nonsense, let me just say that I may well do that one day, but not before treating this worthless planet like the cheap rental car that it is. Speaking of religion, there seems to be an awful lot of similarities between environmentalism and most religion.
Things used to be great, before humans screwed everything up. Garden of Eden/Pre-Industrial society
Humans must repent for their sins, or face hellish consequences.
Sacrifice must be made.
"If children were brought into the world by an act of pure reason alone, would the human race continue to exist? Would not a man rather have so much sympathy with the coming generation as to spare it the burden of existence, or at any rate not take it upon himself to impose that burden upon it in cold blood?”
Arthur Schopenhauer
Clearly the only proper thing to do is keep looking and refine our theories about what we'd see in either case.
"… claims of evidence for extraterrestrials must be viewed with great skepticism. … really, it would be incredibly lucky for the very first probe sent by humans on a planet-finding mission to discover evidence of an alien civilization."
I have no problem at all with the first statement above. But the second echoes the general comments about the "megastructure" suggestion that are almost universal in the discussion by scientists and those are flat wrong. It is not "unlikely" that alien megastructures are the source of this. And it would not be "incredibly lucky" for us to find them. We have ABSOLUTELY NO IDEA how likely or unlikely it would be for us to detect large-scale artifacts of intelligent technology because we have no idea (aside from having not found them previously) whether such structures are possible (though there doesn't appear to be any impossibilities involved) or if they are, how prevalent they are.
It might be that any use of Kepler-like technology would turn up 5 or 6 "Dyson swarms" or whatever… WE DON'T KNOW. And that's the whole point behind SETI.
We can say with reasonable certainty that we do not live in the Star Trek universe (where you can't swing a dead cat without hitting 3 Klingons, a Ferengi, and two transcended energy beings) but beyond that and the fact that we know intelligent technology CAN evolve, we know nothing about the frequency or extent of technology occurring in the universe.
Jason Wright has noted on his twitter feed that there is no plausible speed of rotation for which the flux would drop 22%. Can you make a counterargument to that?
The Jesus speaking anonymous / secular dude does not realize that those who can appreciate life itself possess (the capacity for) gratitude for their existence (some of us, anyway). There need not be anything "miraculous" about it (speaking of religion), but to call this planet a worthless rental car reveals a deep lack of appreciation for what life permits us to experience. It's arrogant on an extreme degree.
Environmentalism is not a religion. It's the study of the interactions and support of physical mechanics (life). That knowledge (speculation and then research) reveals the interdependency which permits our existence, without which there would be no appreciation by our species. Along the way, because of our nature, we gain gratitude for this opportunity to exist and have life. I cannot see anything wrong with that, but anonymous appears to have forgotten something so elemental that killing himself may well be his exit strategy in the mistaken notion that he is "helping" somehow.
Humans have indeed screwed things up really badly and it is clearly getting much worse, but we're just as much a part of the environment as everything else. The fact that we are here proves that. Because we developed the cognitive capacity to understand our impact means we also developed the ability to appreciate our existence (and take notice). Our notions of good and bad are no longer purely instinctive either, they are cognitive. Therefore, we have opportunity to learn. It is no longer an exclusive evolutionary process for us – it is largely self-directed now through knowledge and science. But that doesn't make the Earth a pair of cheap socks to be tossed out, on the contrary, it makes the Earth the exact opposite. Something we should cherish and appreciate because we now have the ability – and through this same knowledge and ability it is very clear that we should do this – or we WILL perish.
All life seeks to survive. Nihilism is human specific, but it is obviously as evolution has shown, unique to our species and not a survival strategy (more likely, it is a mental illness).
The human birthplace should not be derided or discarded or abused now that we understand. Discarding our cognitive capabilities and gained knowledge is actually anti-evolutionary, a reversal of what evolution has clearly created. We are the result of this development.
There are obvious moral reasons (human constructs) why we should cherish and appreciate the Earth, but also physical, life-force reasons which we continue to better understand. The nihilist claims that we have no obligation to respect what sustains us all isn't an evolutionary outcome. There is nothing "religious" about any of this. ~Jonathan Richards~
"what life permits us to experience." Yes, it's called subjective nonsense.
You don't like this philosophy because it is anti-life, so you label it nihilism. Biological life must feed on other life to survive, often in very violent and painful ways. You don't care, because look at the pretty flowers. The earth is a giant mass of mutating, mindless lifeforms. It's a Lovecraftian monstrosity, the sooner it's gone the better. The earth is going away, whether you like it or not. Good riddance.
"no obligation to respect what sustains us all "
Should I respect earthquakes? Should I respect tornadoes? How about hurricanes? Viruses? When I watch a baby seal being eaten alive by a shark, should I smile? Your nature is an abomination. You have replaced "god" with nature and science because you need to maintain a romantic connection to existence. There is no god, and nature is dangerous and irrational. Since we are a product of nature, science is dangerous and irrational. This is where I differ from Ayn Rand types, I reject both nature and science.
It seems unlikely that the three dips at 1500 are unrelated to one another. What about combining your concept with the transit of a planet with a very large, distant ring? The middle dip with symmetrical "wings" at 1540 is the planet transiting the bright zone of the star, while the outer prominent dips at 1520 and 1570 are the two transits of the planet's ring over that bright zone. The outer dips are not equally separated in time from the middle dip because the plane of the ring is at an angle to that of the planet's orbit and the planet's transit is somewhat off the star's bright zone.
Illogical conjecture. Human experience is subjective, but calling it "nonsense" is why your views are indeed nihilistic. For whatever reason, you hate life (all of it). Signs of mental illness.
More signs – you think "not caring" is somehow better then caring (taking an interest). Rocks take no interest as far we can tell – but our development permits us the opportunity (and luxury) to "care". Clearly you don't – another sign of nihilism.
The rest of your screed (Part II) is straw arguments (and also entirely pointless). There is nothing "romantic" about nature or the brutality of its existence, but that does not negate our species from gratitude or appreciation for our existence, or the recognition that without this "brutal nature" (and all that it conveys) we would not be here. The fact that we CAN be appreciative is entirely lost on you. It is not a religion – it is knowledge, but you're too stupid to even realize that. How utterly sad.
You need to get your head examined. As a product of nature, you're severely flawed, hating life and quite probably, yourself. Rejecting science is rejecting knowledge. You may not appreciate the computer your writing on, but you're certainly using it, which according to your bastardized philosophy, shouldn't even be. But it is and therefore you are a hypocrite to boot. ~JR~
"without this "brutal nature" (and all that it conveys) we would not be here." Is being here, better than not being here? When you're asleep, is that an inferior state compared to when you're awake? Are the non-existent in an inferior state? Can you prove that existence is superior to non-existence?
"You need to get your head examined. As a product of nature, you're severely flawed, hating life and quite probably, yourself." Yes, telling the truth about the nature of existence has always led to persecution. Just ask the Cathars, you aren't Catholic are you? Wait, the new Pope has been talking a lot about climate change.
"The will, ignited by the knowledge that non-being is better than being, is the supreme principle of morality.”
Phillip Mainlander
An oblate star sounds like the most probable of all the possibilities I've read about, but I'm a layman. In any case I have a few questions:
1. KIC 8462852 is an F-type main-sequence star, but can F-type star be also oblate?
2. Shouldn't objects passing in front of oblate star still radiate in the infrared?
3. You state the 1st planet is large, occluding 20% of the star's disk, and the second occludes 8%, yet Phil Plait, in his article, says, "Straight away, we know we’re not dealing with a planet here. Even a Jupiter-sized planet only blocks roughly 1 percent of this kind of star’s light, and that’s about as big as a planet gets. It can’t be due to a star, either; we’d see it if it were." If Phil Plait is correct, then that would mean you're not only mistaken about what is occluding the star but also that it's oblate. So, who is right?
OK this is interesting, but can a planet be big enough to occlude 20% of a star? The disk can be a bit smaller due to brightening/darkening, but surely we are still talking about at least a brown dwarf scale object? Which should be detectable?
@kashkrupa: Good questions.
1. We have at least one example of an oblate F-type star with gravity darkening: Beta Cassiopeiae.
2. I'm sure that transiting objects do radiate in the infrared, but I assume that the signal is overwhelmed by the star's IR radiation.
3. The 20% flux decrease is large, and you should always trust Phil Plait's opinion on astrophysical matters before mine. I don't think the category of the object changes the analysis: something big transiting a non-uniform disk.
I am still conscious (aware) when I am asleep. Straw argument. And no, I am not a christian.
Your nihilism is fact, but you are dishonest in all of your arguments. You do not hate life or all physical existence as you claim, you’re still clinging to both.
Moreover, this is incorrect – “The will, ignited by the knowledge that non-being is better than being, is the supreme principle of morality”
The will is ignited (made possible) by life and existence itself, both which bring knowledge. Non-being is no will, no knowledge, no awareness, nothing. Claiming that a principle, let alone “supreme” principle can exist without will or knowledge or existence or laying any claim to any concepts of morality or the existence of morality as a non-being is absurd. Your arguments make absolutely no sense at all.
You’re obviously in a tail-spin, hating everything – the whole of physical reality for whatever reason. You’re missing out on what appears to be an incredible opportunity of existence and life. Why you chose this and hate it so is secret to you. You’re confusing the physical nature of reality and existence with your bastardized philosophy of why existence is wrong.
There need be “no reason for our existence” (Noam Chomsky) but that does not mean that we have no reason to not appreciate it (or to recognize any of its good). Taking opportunity is what physical existence does. Life goes even further, and consciousness further yet.
You’ve attempted to bastardize this ability (existence, life, consciousness, knowledge) to try and refute all physical existence itself. Obviously, it does not work that way.
Enough. You’re dangerously deluded, contradicting at every step. You’re just another fool making nonsensical claims and circular reasoning, driven by a gross misunderstanding of your existence.
~JR~
P.S. Sorry Jim – I’m done here.
There is an oversight here that should be corrected in the blog.
It should be pointed out that the original theory paper by Barnes, et al, about the dimmings at PTFO 8-8695 being caused by giant planets crossing a gravity darkened, oblate star, were strongly refuted by a later study.
'Tests of the planetary hypothesis for PTFO 8-8695b'
http://arxiv.org/abs/1509.02176
This model doesn't work for planets at PTFO 8-8695 and definitely doesn't work to explain the 8462852 light curve. Sorry folks.
And here is me being excited at another possible theory for KIC 8462852
Hello,
Thanks for the article, it was very interesting.
Just a very dumb question. If there is such a huge planet orbiting this star (3-4 times the mass of Jupiter) wouldn't it affect to the star orbit and modify it to have a baricenter? Could analyze the orbit of this star and conclude whether a huge mass object is affecting their orbit?
Regards,
Oscar
This is really good stuff – you might not be right – but the simple idea that it's the star! is the point – also if the star is none hydrostatically stable is it possible that orbits of surrounding planets are not simple elipses?
It's not "solved" at all which is egocentric and presumptuous to say the least. Not to mention gravity darkened oblique stars were already ruled out by the team. They graphs don't even fit as they have huge features that are not in common.
What about Trojans and Hildas? Now I get a little higher percentage of just under 23% dimming but that's not too critical. A Jupiter mass planet can have 60 degree,leading and lagging Trojans, which will act rather like a filter. The Hildas, have really interesting orbits, in that they will have a group of asteroids 180 degrees from the Jupiter mass planet. If they are responsible for the 8% dip, then we could work out the proportion of Trojans to Hildas.
Winter is Coming 😉