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No Catastrophic Collision at KIC 8462852

Last week I mentioned that I wanted to get into Massimo Marengo’s new paper on KIC 8462852, the interesting star that, when studied by the Kepler instrument, revealed an intriguing light curve. I’ve written this object up numerous times now, so if you’re coming into the discussion for the first time, plug KIC 8462852 into the archive search engine to get up to speed. Marengo (Iowa State) is himself well represented in the archives. In fact, I began writing about him back in 2005, when he was working on planetary companions to Epsilon Eridani.

2009-08-20-00004-2

In the new paper, Marengo moves the ball forward in our quest to understand why the star I’ll abbreviate as KIC 8462 poses such problems. The F3-class star doesn’t give us the infrared signature we’d expect from a debris disk, yet the light curves we see suggest objects of various sizes (and shapes) transiting across its surface. What we lacked from Tabetha Boyajian’s earlier paper (and it was Boyajian, working with the Planet Hunters group, that brought KIC 8462 to our attention) was data about infrared wavelengths after the WISE mission finished its work.

That was a significant omission, because the WISE data on the star were taken in 2010, while the first events Kepler flagged at KIC 8462 occurred in March of 2011, with a long series of events beginning in February of 2013 and lasting sixty days. That gave us a small window in which something could have happened — the idea of a planetary catastrophe comes to mind, perhaps even a collision between two planets, or a planet and large asteroid. What Marengo brings to the table are observations from the Spitzer Space Telescope dating from early 2015.

Image: Astrophysicist Massimo Marengo. Credit: Iowa State University.

We learn that the Spitzer photometry from its Infrared Array Camera (IRAC) finds no strong infrared excess — no significant amount of circumstellar dust can be detected two years after the 2013 dimming event at KIC 8462. Here is what Marengo concludes from this:

The absence of strong infrared excess at the time of the IRAC observations (after the dimming events) implied by our 4.5 µm 3σ limit suggests that the phenomenon observed by Kepler produced a very small amount of dust. Alternatively, if significant quantity of dust is present, it must be located at large distance from the star.

This seems to preclude catastrophic scenarios, while leaving a cometary solution intact. The paper continues:

As noted by B15 [this is the Boyajian paper], this makes the scenarios very unlikely in which the dimming events are caused by a catastrophic collision in KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system, or a population of dust-enshrouded planetesimals. All these scenarios would produce very large amount of dust dispersed along the orbits of the debris, resulting in more mid-IR emission than what can be inferred from the optical depth of the dust seen passing along our line of sight to the star. Our limit (two times lower than the limit based on WISE data) further reduces the odds for these scenarios.

Screenshot from 2015-11-30 09:01:06

Image: Montage of flux time series for KIC 8462852 showing different portions of the 4-year Kepler observations with different vertical scalings. Panel ‘(c)’ is a blowup of the dip near day 793, (D800). The remaining three panels, ‘(d)’, ‘(e)’, and ‘(f)’, explore the dips which occur during the 90-day interval from day 1490 to day 1580 (D1500). Credit: Boyajian et al., 2015.

Tabetha Boyajian’s paper analyzed the natural phenomena that could account for KIC 8462’s light curve and concluded that a family of exocomets was the most promising explanation. Here the idea is that we have a family of comets in a highly elliptical orbit that has moved between us and the star, an idea that would be consistent with the lack of a strong infrared signature. Marengo has reached the same conclusion now that we are able to discount the idea of a large collision within the system. Both Boyajian and Marengo favor the comet hypothesis because it does not require a circular orbit and allows associated dust to quickly move away from the star.

In Marengo’s analysis, this fits the data, as the two-year gap between the Kepler light curves and the observations from Spitzer provide enough time for cometary debris to move several AU from the zone of tidal destruction from the star. The paper adds:

At such a distance, the thermal emission from the dust would be peaked at longer wavelengths and undetectable by IRAC. A robust detection at longer wavelengths (where the fractional brightness of the debris with respect to the star would be more favorable) will allow the determination of the distance of the cometary fragments and constrain the geometry of this scenario.

So we have a way to proceed here. Marengo notes that the measurements his paper presents cannot reveal the temperature or the luminosity of the dust that would be associated with such a family of comets, but long-term infrared monitoring would allow us to constrain both. The other day I also mentioned the small red dwarf (about 850 AU out) that could be the cause of instabilities in any Oort Cloud-like collection of comets around KIC 8462. Boyajian’s paper makes the case for measuring the motion or possible orbit (if bound) of this star as a way to tighten predictions on the timescale and repeatability of any associated comet showers.

Marengo dismisses SETI study of KIC 8462, with specific reference to Jason Wright’s recent paper on the matter, as “wild speculations,” an unfortunate phrase because Wright’s shrewd and analytical discussion of these matters has been anything but ‘wild.’

The Marengo paper is Marengo, Hulsebus and Willis, “KIC 8462852 – The Infrared Flux,” Astrophysical Journal Letters, Vol. 814, No. 1 (abstract / preprint). The Boyajian paper is Boyajian et al., “Planet Hunters X. KIC 8462852 – Where’s the flux?” submitted to Monthly Notices of the Royal Astronomical Society (preprint). The Jason Wright paper that examines KIC 8462 in the context of SETI signatures is Wright et al., “The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures,” submitted to The Astrophysical Journal (preprint).

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  • Harry R Ray November 30, 2015, 14:48

    What this paper fails to discuss is the OVERALL activity associated with KIC84628522. This activity is clear right from the ONSET of the Kepler observations. I have broken them down as follows: Active(300 days) with 2 signifigant(although NOT major dimming events; quiescent(200 days); active(150 days) with the 3-5 day major event at the END; quiescent(300 days); active(400 days0 leading up to the final series of major events. Since BOTH major events were PRECEDED BY prolonged activity, it is quite logical to assume that a prolonged activity cycle and a major event are indeed associated with each other somehow. The prolonged period of quiescence IMMEDIATELY AFTER the first major event is very strange indeed. If this was a result of comet fragmentation, the lack of ANY RESIDUALS after EGRESS of the clump responsible for the first major event is a much better fit if the clump were moving TOWARD the star, rather than away, as is implied in the paper. I guess we’ll just have to wait for 2017 to see if there is another major event to pin down the orbital period of whatever it is that is causing the dimmings.

  • H. Floyd November 30, 2015, 15:55

    Layman’s question. I’ve been reviewing the Boyajian, Wright and Marengo professional discussions with great interest but am not tracking the big conclusion making headlines now. How does the Marengo study either prove or eliminate the favored cometary explanation or the disfavored ETI hypothesis?

    Please insert the usual disclaimers that exotic ETI theories must always be disfavored over natural explanations. No question about that. But both theories are based on observed data, are eventually testable, and are therefore disprovable if wrong. They’re valid theories, albeit not equally plausible. And lack of IR radiation seems to support Boyajian’s proposed explanation and reasons for eliminating other natural explanations — as well as it supports the ETI hypothesis.

    So doesn’t the latest analysis simply further narrow the inquiry to the two hypotheses that Dr. Boyajian and Dr. Wright placed on the board?

  • Horatio Trobinson November 30, 2015, 16:25

    Given a 20+ dimming, the size and composition of comets, if they are comets, seems to be something unlike anything we have seen in comets before.
    I wouldn’t discount the possibility of a dark planetary system sitting between KIC 8462852 and us.
    Have you seen anybody proposing anything like that?

  • Volucris November 30, 2015, 17:52

    Horatio: Interesting! If it was something between us and the star, then the events should not repeat themselves ever again, intervening object moving away from the line of sight. I guess we’ll find out.

    I’m just waiting to see the transmission spectrographs when/if the events repeat. Spectrographs certainly should come out with lots of detail, as the objects block such a huge proportion of the light.

  • ljk November 30, 2015, 17:54

    Horatio Trobinson said on November 30, 2015 at 16:25:

    “Given a 20+ dimming, the size and composition of comets, if they are comets, seems to be something unlike anything we have seen in comets before.

    “I wouldn’t discount the possibility of a dark planetary system sitting between KIC 8462852 and us.”

    Yes if those are a swarm of comets circling that star, it is one heck of a flock. And the star is not young so we cannot blame this on the age of the system. We are aware of other star systems having lots of comets – Tau Ceti comes to mind off the top of my head – and yet they are not blotting out entire regions of their sun. Again this could be a new type of comet swarming we have not seen before due to our relative cluelessness about such things, but it does seem odd that there are not more of them.

    In regards to your comment about a “dark planetary system”, can you explain what you mean by that?

    It is only safe and smart to have scientists look for natural, nonintelligent design reasons for such things as is happening around KIC 8675309, but when they start backpedaling and dismissing the possibility for ETI as noted in the article about the paper, then it does not help in terms of expanding our knowledge and awareness. I think they know this is one “weird” discovery and that conventional answers just are not quite cutting it yet, but it is sad to see that the word “alien” can still make professionals scamper for various reasons. We are still quite provincial as a species.

  • Massimo Marengo November 30, 2015, 19:42

    We didn’t address the activity before the Kepler’s event because our only window on the phenomenon was at the time of the Spitzer observations, years later. The only question we could address with our available data was the relatively rapid clearance of infrared-bright material after the second set of events. The overall sequence of main events in the Kepler’s data was already well described in the Boyajian paper. Concerning the activity preceding the events, it has been noted by the Kepler’s group, as well as by us, but it will require more detailed analysis to ensure that is real, and not the result of artifacts in the light curve normalization processing.

    We did not address the ETI hypothesis because there is nothing in the Spitzer data that would support or disprove it. It should be noticed, however, that any structure around the star (whatever its origin) should still obey the laws of thermodynamics. As such it will have the same requirements to irradiate at infrared wavelengths, in order to dissipate the heat absorbed by occulting the light from the star. For this reason, our observations cannot really say anything about the ETI hypothesis. The usual disclaimer about exotic theories, however, is key, and we are very far from exhausting natural explanations for the phenomenon observed around this star at this point, implying that natural and ETI scenario are not, at this point, on equal footing.

    Yes, the comets scenario proposed by Boyajian et al., and supported by our non-detection of infrared radiation, involves objects that are not the usual comets we see in the Solar System. We are talking about a very large object (think of some icy Kuiper belt object) that had the misfortune to be sent too close to the star. A “dark planetary system” (i.e. a lone cold planet without a central star, because anything else would not be dark, at least in the infrared) would only transit once in front of the star, due to the relative motion of stars in the Galaxy. Any single cause producing multiple events needs to be close to the star.

    A scenario involving non-natural causes is still “wild”, at this point, since it is unsupported by the available observational evidences (at least until, as I mentioned before, all natural causes have not yet been discounted). This is something Wright et al. make very clear in their discussion. That said, I fully agree that the analysis in the Wright et al. paper is sound, and that entertaining this kind of scenarios is worth doing. With the term “wild” we didn’t mean to discredit Jason’s paper; the term was only meant to refer to the speculative nature of that hypothesis.

  • Eniac November 30, 2015, 21:55

    Horatio and ljk: It is quite obvious that the dimming is not caused by a solid object, as such a solid object would have to be nearly the size of the star. So, no “dark planet”, or gigantic comet swarm. Any old comet, on the other hand, has a tail that is like a cloud of dust, it can be very large and it is entirely plausible (to me) that it would produce the dimming that is observed. The swarm part is not needed for the amount of dimming, only to explain why there are multiple irregularly spaced events.

    See this for the size of a comet’s tail:

    While the solid nucleus of comets is generally less than 50 km across, the coma may be larger than the Sun, and ion tails have been observed to extend 3.8 astronomical units

    https://en.wikipedia.org/wiki/Comet_tail#Size

    Massimo: You, like Paul, also state that the phenomenon likely “involves objects that are not the usual comets we see in the Solar System”. Could you perhaps elaborate on why you think so? Are there quantitative models that predict the dimming that a comet tail would cause when passing in front of a star? Do such models show that a regular comet is not sufficient?

  • Michael December 1, 2015, 3:47

    @Massimo Marengo

    Could it be a stellar grazing planet in a very eccentric orbit with an evaporating moon forming a ring system that has an aphelion towards us? An aphelion towards us would give a slower transit time as seen in the light curve. As this star is also a fast spinner so could it be that near the Star its stellar wind/magnetic field smears out the materials emitted from the moon and this is the distortion in some parts of the light curve. I am trying to find out what materials can be emitted from the moon that would not produce a IR excess, I find sulphur dioxide to be highly reflective in the UV.

    http://exoplanetarchive.ipac.caltech.edu/cgi-bin/ICETimeSeriesViewer/nph-ICEtimeseriesviewer?inventory_mode=id_single&idtype=source&id=8462852&dataset=Kepler

  • Simon Farmer December 1, 2015, 5:13

    I decided to use a popular game creation program (Unity) to create a simple simulator for objects moving in front of a star. It was simple, in that the star was white, and the transiting object was black. Light curves were created by getting the total percentage of black to white pixels. After this was done, I was able to replicate quite the basic light curve quite easily. Then I was free to try whatever objects I wanted, boxes, cylinders, multiple spheres, etc. Any basic shape that I tried basically had a similar result to a transiting sphere. Probably the most interesting result I got was being able to replicate the basic shape of the light curve at day 1540 – I did it by having a large ring shape rotate around its vertical axis during a single transit. The software is pretty rough, and not really meant for public consumption, but if there is interest in seeing the objects create the light curve I can work on it some more.

  • Michael December 1, 2015, 10:27

    @Simon Farmer December 1, 2015 at 5:13

    ‘I decided to use a popular game creation program (Unity) to create a simple simulator for objects moving in front of a star. It was simple, in that the star was white, and the transiting object was black…’

    I have downloaded the software and will try it out later but I have to go see a Rock Band, Judas Priest, tonight. You could try changing the outer circle to an ellipse around the circle in the centre to get the tilt of the rings. It is my belief it is a planet/moon responsible for this light curve.

  • Harry R Ray December 1, 2015, 10:56

    Massimo: A new paper on the exoplanet.eu website today strongly supports your theory and Boyajian et al’ hypothesis, but ONLY for the hyper-chaotic final 80 day events. The authors stste that ALL of these events could be caused by a loosely bound family of approximately 750 UNFRAGMENTED(adding fragmentation to the mix made Boyajian et al’s hypothesis seem a little bit TOO contrived for my taste) comets with just the proper alignments of their dust tails COULD produce the required 20% dip. However, the day750 event was TOO SYMETRICAL for a family of unfragmented comets to produce. Must we invoke a contrived fragmentation mechanism for this event, or could a planet with a very large ring system be a better fit? Finally: Might we resolve this VERY QUICKLY by using the Beta Pectoris analogy? Spectral analysis reveals comets crashing into BetaPic on a very regular basis. Assuming that the event that caused the family of 750(more or less comets to enter the region near the star INTACT would probably cause millions of other comets to enter that region as well, some on extremely eccentric orbits, prompting many comet/star collisions! Is there a telescope available right now that could pick up their spectral signature RIGHT NOW?

  • Harry R Ray December 1, 2015, 11:11

    Massimo: If you haven’t read it already, the papre mentioned in my above comment to you is: KIC8462852: Transit of a Large Comet Family: By Eva H. L. Bodman, Alice Quillan.

  • Massimo Marengo December 1, 2015, 18:02

    @Harry R Ray: thanks for the head’s up (I had missed the preprint). I read the article and yes, it pretty much agrees with the comet swarm scenario advanced by Boyajian et al. and by us (assuming that their model is consistent with the lack of IR excess in January 2015, which they are not yet considering).

    Note that when we talk about “family of comets” all we mean is that a larger body is somehow fragmented, producing a number of smaller entities with similar orbital parameters. Each fragment would behave as an individual comet by naturally developing a coma and tail. This scenario is much more likely than separate comets entering the proximity of the star within a short time span. Fragmentation of comets is something quite natural (not contrived at all). In fact it regularly happens to the Solar System “Sun grazing” comets, due to the thermal and tidal stress they experience at aphelion. Another example is the SL-9 comet that first fragmented, and then crashed onto Jupiter in 1994 (in this case the fragmentation was due to Jupiter’s tidal stress). So, the family of comets we propose, successfully exploited in the Bodman & Quillen model, can be easily explained by a large ice-covered body (something like the Solar System Kuiper belt objects) that broke up by passing too close to the star.

    Right now the cometary fragments would be quite far from the star, and sub-mm observations are required.

    To everybody that is proposing a large solid object to block the light of the star: that won’t work. Any object sufficiently large would be crushed into a sphere on its own gravity. That is why only small asteroids have a lumpy shape: anything as big as Vesta has a round spherical shape (e.g. Ceres). So any structure capable to block as much as 20% of the light of a star cannot be a single body; it need to be a collection of smaller particles, such as the dust debris in the tail of a comet, blown over a very large area by the radiation and wind of the star.

  • Horatio Trobinson December 2, 2015, 4:20

    @ljk, @Massimo, @Eniac, @Harry

    By ‘dark planetary system’ I mean a group of starless, rogue planets sitting between KIC 8462852 and us.
    Given enough distance, due to angular coverage, such objects wouldn’t need to be extremely large, nor should they have the extension of a comet’s tail.

    This could even be compatible with something Harry R Ray posited above, that the objects might moving towards the star.
    If we are able to monitor and determine an orbit cycle, and this is a group of planet-like, non-cometary objects moving towards KIC 8462852, we should observe a progressively reduced dimming for all shadow events.

  • Horatio Trobinson December 2, 2015, 4:34

    Addendum:

    Even if there’s a cometary system, or a dark planetary system between the star and us, neither of these scenarios preclude the possibility that there might also be some dimming events caused by legitimate KIC 8462852 planets.

    It’s not impossible to conceive we might have a superposition of simultaneously dimming events from two, or even three of these possible scenarios.

  • ljk December 2, 2015, 10:45

    How about Dyson Swarms in the shape of donuts (just don’t tell Homer Simpson):

    http://burtleburtle.net/bob/scifi/dyson.html

  • ljk December 2, 2015, 11:36

    Why hasn’t a bigger deal and correlation been made with this other KIC object, which is being blamed on a the disintegration of an exo Super Mercury type world:

    http://arxiv.org/abs/1201.2662

    Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548

    http://arxiv.org/abs/1403.1879

    Multiwavelength Observations of the Candidate Disintegrating sub-Mercury KIC 12557548b

    I posted these links in one of the first Centauri Dreams article on KIC 8462852 but there were no comments on them.

    Again, if this alien “comet” is just really big compared to the comets we are used to, why not go for broke and call it an exoplanet as has been done with KIC 12557548?

    And may I say again those few paltry radio SETI efforts and the subsequent declaration in the media and elsewhere that no signals = no aliens is hardly proper scientific research. I do not want to see Tabby’s Star ultimately dismissed in a similar manner, as we need to ask ourselves: In light of the fact that it was found in a very narrow sky search by Kepler, does this mean we either got very, very lucky spotting a rare event or are there a lot of them out there?

    Jason Wright has an excellent blog on this celestial phenomenon. Here is his latest posted article on the topic:

    http://sites.psu.edu/astrowright/2015/10/15/kic-8462852wheres-the-flux/

  • Massimo Marengo December 2, 2015, 13:44

    One last comment about “dark” planets: when you say “dark” you need to specify at which wavelengths. Planets, if not illuminated by a nearby star, are dark in the visible light, but they are all very bright in the infrared. Given that there is a maximum radius planets can have (not much bigger than Jupiter), to cover 20% of the light of a distance star they would need to be quite close to the Solar System, and as such they would be easily detectable from Earth in the infrared, especially at 4.5 micron, where gas giant emission is maximum. And without a star keeping them together, you won’t have more than a single isolated planet, preventing the possibility of multiple transiting events, as I explained above. And exotic massive “dark” objects are also excluded, because they would cause gravitational microlensing during the transit, which have the opposite signature on the light curve (microlensing causes brightening).

  • H. Floyd December 2, 2015, 14:44

    Thermodynamics. My mistake, an embarrassing one. I assumed the ETI hypothesis involved super-low-waste technology. I suppose I was analogizing to fiber optics: functioning at low IR frequencies with low leakage.

    Yesterday I read earlier papers by Dr. Wright and colleagues, and they couldn’t have been clearer about avoiding that assumption: “Naively, it would seem then that ETIs with large energy supplies would construct highly efficient Dyson spheres, potentially rendering waste heat so cool that it would not radiate in the MIR [mid-infrared]. However, the marginal free energy yield from employing ever lower waste heat temperature decreases . . . even as the difficulty of the engineering rapidly increases. … This strong inverse dependence implies that there will be an optimal waste heat temperature beyond which it would be impractical to extract more free energy from starlight. … Thus, while an alien civilization using starlight might emit waste heat over a range of temperatures, we should not expect it to be so cold or to have such a strongly non-thermal spectrum that as to be easily missed in the MIR.” Wright, et al., 2014b, Part 2.6.4.

    The Spitzer/IRAC data for IR frequencies above thresholds of 3.6 and 4.5 micrometers are where the ETI hypothesis predicts we would see Dyson waste energy, and it wasn’t there. That, combined with the recent SETI observations by Harp, et al. (which I also first underappreciated), shows lots of informative quiet out there at Boyajian’s Star.

    Dr. Wright offers much more than waste energy predictions, including ten anomalies by which to distinguish an ETI candidate. 2015 preprint, Table 1. The observations at Boyajian’s Star are uniquely consistent with a few of those, which excites the “wild” public (raising hand). But those observations are also consistent with confounds that Dr. Wright identifies in the same Table. So the Spitzer/IRAC data are particularly valuable.

    Dr. Marengo has patiently responded here that his team’s findings don’t address the ETI hypothesis, but I would have been better asking the opposite question: Don’t they?

  • H. Floyd December 2, 2015, 15:40

    (Correction: wavelengths, not frequencies.)

  • ljk December 2, 2015, 17:34

    Speaking of strange cosmic objects that make people wonder if they are signs of advanced ETI, the jury is still out on Fast Radio Bursts:

    http://www.scientificamerican.com/article/fast-radio-bursts-mystify-experts-for-now/

    To quote:

    “Still, the sources for FRBs remain unknown. What could cause such intense, frequent events? Researchers have proposed so many answers over the years that there are now more theories for FRB origins than there are observed FRBs.”

  • Harry R Ray December 4, 2015, 11:17

    ljk: A DISCARDED Shkadov Thruster with a substantial ammount of its mirrors NO LONGER ATTACHED would look JUST LIKE a Dyson swarm in the shape of a donut. Please seek out my Shkadov Thruster ideas in PRIOR COMMENTS in posts where the subject matter is KIC8462852.

  • ljk December 4, 2015, 14:25

    Harry R Ray, is there any indication of an unusual acceleration of KIC8462852?

    Unusual for a “regular” star moving through the galaxy, that is.

  • Harry R Ray December 6, 2015, 14:24

    ljk: If there IS(again, HIGHLY improbable) a Shkadov Thruster between Earth and KIC8462852, it would have most certainly NOT have been(or being right now) used to accelerate KIC8462852. The only two scenarios for one to be there BOTH involve the M2V companion. SCENARIO ONE: Rescources around the M dwarf started to become scarce, and it was moved into ORBIT around KIC8462852 to exploit a NEW source of minerals. SCENARIO TWO: KIC8462852 has JUST evolved OFF the main sequence, and the M dwarf was moved from a PREVIOUS orbit that was CLOSER to KIC8462852, to its present location. In BOYH SCENARIOS, the Shkadov Thruster was JETTISONED, but still remains in orbit around KIC8462852.

  • Harry R Ray December 6, 2015, 15:12

    Oh, by the way. KIC8462852’s M2V companion was discovered by the WISE spacecraft(and CONFIRMED by the Keck telescope). Has the WISE team givin it its OFFICIAL WISE designation number yet? Anybody know? RSVP.

  • Massimo Marengo December 6, 2015, 16:52

    The possibility that KIC 8462852 was a visual binary was first speculated by Boyajian et al. based on the asymmetry of the UKIRT (a ground based infrared telescope in Hawaii) near-R image. This was later confirmed using the Keck telescope (with adaptive optics). WISE did not have the resolution of the photometric accuracy to detect the companion.

    Note also that at this stage this is only a candidate companion. There is still ~ 1% possibility that the source is a background cool star (e.g. a red giant) in a chance alignment with KIC 8462852. The best way to confirm that this is a true companion (an M2V star) is to obtain a high resolution spectrum of the star and measure its surface gravity (which would be very different from the surface gravity of a M2III background red giant). Not easy to do, however, since it is 3.5 magnitude fainter and less than 2″ from the primary star.

  • Simon Farmer December 7, 2015, 2:47

    Could anyone comment on how this might be similar to GJ 436b? It’s the only recent article I remember reading that talked about dimming a star so much, a sci-news article:

    http://www.sci-news.com/astronomy/science-gliese-436b-comet-like-tail-02951.html

    I can imagine some sort of close in planet having a “variable atmosphere” and interaction with the parent star that might explain the lack of IR.

  • Harry R Ray December 7, 2015, 10:25

    Simon Farmer: Gliese 436b’ s “behemouth” is ONLY visible in the ULTRAVIOLET SPECTROM! It does NOT block any VISIBLE LIGHT from Gliese436 at all!

  • LeRoy Westerling December 7, 2015, 12:36

    Why are ETI hypotheses referred to here as unnatural causes? Humans arose on this planet through natural evolutionary processes.

    Why shouldn’t ETI hypotheses be entertained at this point? The probability of ETI in any single star system is unknown but low. However, as the number of observed star systems grows, surely so too does the probability that ETI is present in one or more of those systems?

  • ljk December 9, 2015, 15:16

    Well, they took a peek for laser signals from Tabby’s Star and nada, so no aliens making Dyson Swarms even moreso now, of course:

    http://setiinternational.org/no-extraterrestrial-laser-pulses-detected-kic-8462852-new-seti-organization-reports

    But that’s okay because we’re probably going about SETI and METI all wrong (certainly in terms of financial support, resources, and trying other methods, to be sure):

    http://www.leonarddavid.com/making-contact-with-etdoomed-to-failure/

    Meanwhile here is a new brief history of mainstream SETI hitting all the usual highlights:

    http://www.vice.com/read/a-brief-history-of-scientists-searching-for-extraterrestrial-life-124

    And here is a far more detailed, open, and honest assessment of SETI history and why we have yet to find aliens of any sort:

    http://www.daviddarling.info/encyclopedia/S/SETI_critical_history_cover.html

  • ljk December 10, 2015, 9:41

    SETI International changed the URL regarding the Optical SETI story:

    http://setiinternational.org/blog/no-extraterrestrial-laser-pulses-detected-kic-8462852-new-seti-organization-reports

    They also have a blog piece on Optical SETI in Panama:

    http://setiinternational.org/blog/optical-seti-panama

    And SETI historian Steven J. Dick weighs in on METI with this insightful piece:

    http://setiinternational.org/blog/should-we-message-et

  • Mark Zambelli December 10, 2015, 11:05

    @LeRoy,
    I agree that any musings about ETI should be considered in the mix but it should rightly play a minor role in our quest to explain anomolous findings until we have a bigger sample size than just ourselves. This way we can proceed to exhaust any natural explanations first. For example, we know we exist but we do not know if anybody else does. Conversely, we know the Universe works through many varied natural phenomena and we absolutely know that we are aware of only a proportion of these phenomena so we strive to understand more examples and explain them as we do science. This way I would choose to rephrase the term ‘un-natural’ to ‘artificial’. That way, intelligent life is ‘natural’ but signs of that intelligence would be ‘artificial’.

    I’d like to thank Massimo Marengo for his input here; it’s a privilege to have the authors of papers here from time to time to help clarify things and it’s greatly appreciated, thanks again for taking the time.

  • ljk December 10, 2015, 13:41
  • ljk December 11, 2015, 12:33

    And if Tabby’s Star was surrounded by a Dyson Swarm or some other artifact of alien intelligence…

    http://setiinternational.org/blog/so-what-if-kic-8462852-did-have-alien-megastructures

  • ljk January 12, 2016, 10:31

    New article on Tabby’s Star:

    http://scienceline.org/2016/01/tabbys-mystery/

    To quote:

    “I like the comet explanation although ‘comet’ might not be the right word,” says Eric Korpela, another astronomer from the Berkeley SETI Research Center. That’s because the core of such an object would have to be as large as Pluto in order to generate this kind of light, he explains.

    Korpela and other astronomers believe the dimming may be due to some kind of natural phenomenon we haven’t yet seen anywhere in the universe. “We just haven’t looked at enough stars to know what’s out there,” he says.

    and…

    Other ground-based telescopes that will be pointed at Tabby’s star in the near future include the Green Bank Telescope in West Virginia, the MINERVA array in Arizona, the MEarth telescopes in Arizona and Chile, and the LOFAR telescope in the Netherlands. Even amateur astronomers from the American Association of Variable Star Observers will be joining in with their home telescopes.

    The Green Bank Telescope appears the most promising avenue for studying Tabby’s star because it’s 100 times more sensitive than most telescopes, such as the Allen Telescope Array, that have already looked at the star, says Berkeley’s Siemion. It’s so sensitive that it can detect energy equivalent to a single snowflake hitting the ground. The team is also installing brand-new instrumentation that will allow them to study radio waves in much greater detail, Siemion says.

    Astronomers studying Tabby’s star are particularly excited for May 2017, because if the dimming is indeed due to a broken-up comet, that’s when it would likely be passing in front of the star again. As Catanzarite says, “This isn’t the end of the story.”