I hadn’t expected a new paper on KIC 8462852 quite this fast, but hard on the heels of yesterday’s article on the star comes “KIC 8462852 Faded at an Average Rate of 0.165±0.013 Magnitudes Per Century From 1890 To 1989,” from Bradley Schaefer (Louisiana State University). Schaefer takes a hard look at this F3 main sequence star in the original Kepler field not only via the Kepler data but by using a collection of roughly 500,000 sky photographs in the archives of Harvard College Observatory, covering the period from 1890 to 1989.
The Harvard collection is vast, but Schaefer could take advantage of a program called Digital Access to a Sky Century@Harvard (DASCH), which has currently digitized about 15 percent of the archives. Fortunately for us, this 15 percent covers all the plates containing the Cygnus/Lyra starfield, which is what the Kepler instrument focused on. Some 1581 of these plates cover the region of sky where KIC 8462852 is found. What Schaefer discovers is a secular dimming at an average rate of 0.165±0.013 magnitudes per century. For the period in question, ending in the late 1980s, KIC 8462852 has faded by 0.193±0.030 mag. From the paper:
The KIC 8462852 light curve from 1890 to 1989 shows a highly significant secular trend in fading over 100 years, with this being completely unprecedented for any F-type main sequence star. Such stars should be very stable in brightness, with evolution making for changes only on time scales of many millions of years. So the Harvard data alone prove that KIC 8462852 has unique and large-amplitude photometric variations.
That’s useful information, especially given the possible objection to the Kepler findings that they might be traceable to a problem with the Kepler spacecraft itself. Evidently not:
Previously, the only evidence that KIC 8462852 was unusual in any way was a few dips in magnitude as observed by one satellite, so inevitably we have to wonder whether the whole story is just some problem with Kepler. Boyajian et al. (2015) had already made a convincing case that the dips were not caused by any data or analysis artifacts, and their case is strong. Nevertheless, it is comforting to know from two independent sources that KIC 8462852 is displaying unique and inexplicable photometric variations.
As Schaefer notes, KIC 8462852 can now be seen to show two unique episodes involving dimming — the dips described here yesterday for the Kepler spacecraft, and the fading in the Harvard data. The assumption that both come from the same cause is reasonable, as it would be hard to see how the same star could experience two distinct mechanisms that make its starlight dim by amounts like these. The timescales of the dimming obviously vary, and the assumption would be that if the day-long dips are caused by circumstellar dust, then the much longer fading that Schaefer has detected would be caused by the same mechanism.
Image: KIC 8462852 as photographed from Aguadilla, Puerto Rico by Efraín Morales, of the Astronomical Society of the Caribbean (SAC).
Thus we come to the comet hypothesis as a way of explaining the KIC 8462852 light curves. Incorporating the fading Schaefer has discovered, a cometary solution would require some mind-boggling numbers, as derived in the paper. From the summary:
With 36 giant-comets required to make the one 20% Kepler dip, and all of these along one orbit, we would need 648,000 giant-comets to create the century-long fading. For these 200 km diameter giant-comets having a density of 1 gm cm?3, each will have a mass of 4 × 1021 gm, and the total will have a mass of 0.4 M?. This can be compared to the largest known comet in our own Solar System (Comet Hale-Bopp) with a diameter of 60 km. This can also be compared to the entire mass of the Kuiper Belt at around 0.1 M? (Gladman et al. 2001). I do not see how it is possible for something like 648,000 giant-comets to exist around one star, nor to have their orbits orchestrated so as to all pass in front of the star within the last century. So I take this century-long dimming as a strong argument against the comet-family hypothesis to explain the Kepler dips.
If Schaefer’s work holds up, the cometary hypothesis to explain KIC 8462852 is deeply compromised. We seem to be looking at the author calls “an ongoing process with continuous effects” around the star. Moreover, it is a process that requires 104 to 107 times as much dust as would be required for the deepest of the Kepler light dips. And you can see in the quotation above Schaefer’s estimate for the number of giant comets this would require, all of them having to pass in front of the star in the last century.
The paper is Schaefer, “KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989,” submitted to Astrophysical Journal Letters (abstract).
On the transient change, if it takes 5 years for the transition to complete, and stellar life is 5 billion years, there is, at first glance, a one in a billion chance of seeing it happen on any particular star. So, if we observed a billion F3 low-metallicity stars for a year or however long it takes to see the change, we would see another one. Good hunting!
The implied orbital velocity of the dips that Tabby’s Star showed in Kepler is very slow, so the equilibrium temperatures might be estimated to be pretty low (~100 K or so, very roughly).
I must have misread something, I was under the impression that the dips lasting about a day meant the obscuring objects were fairly close to the star, the Earth, as an example, would, at an orbital speed of 30km/s, take about 13 hours to transit the Sun as seen from interstellar distances if the transit was across the maximum wide of the solar disc. So something directly orbiting the star and taking 24 hours to cross the disc of a F class star would be further from the star than Earth from the Sun, but would still be getting a similar (I would have thought a greater) level of EM radiation as the Earth, so be emitting IR at temperatures way above 100K.
Jason: Another ETI exotica is that the stellar energy could be converted to antimatter (or some other energy storage) and used elsewhere or later. For example, if you wanted to do a lot of long-distance travel it might be nice to have an antimatter source, and that energy would show up as waste heat elsewhere.
I of course don’t like such explanations without good cause; they “multiply entities” unnecessarily. But, yes, it is important to recognize that the thermodynamics arguments are not iron-clad for ETI.
Thank you Prof Wright for the detailed explanation! I didn’t grasp the necessary drop in entropy for re-beaming, but you certainly cleared it up.
Jason Wright: Thanks! That beats guesswork any day! (Thanks, also, to whoever it occurred to to just call that in directly.) Everyone’s discretely favored “dark” horse has survived the comet attack and is still in the race. Back to the edge of my seat.
Jason Wright January 17, 2016 at 22:16
“b) Energy-to-mass conversion: this is essentially super-efficient energy storage. Kind of a waste though, since if you wanted mass there’s plenty of it right there in the star, or in whatever you’re making the absorbers out of— there’s no reason I can think of to make piddling amounts of mass out of starlight.”
Perhaps they’re creating antimatter and storing it for later use, perhaps for propulsion. Maybe look for x-ray emissions from matter-antimatter annihilation.
As a semiconductor device person, I am an astronomy-enthusiast, not a professional, so please bear with me if I am asking silly questions.
I was wondering if we can image this star in near and far UV as well as in X-ray (is it already done?)
If we can collect data on the spectra of the star from, say, 200 nm to 16 micron wavelength over time, then would it be possible to investigate which wavelengths are getting dimmer/fading over time ? I mean, I understand the visible component is fading away but is it that the entire spectra is slowly reducing in intensity (photon flux)? As in, each star has its own black body spectra based on its temperature (for our sun, we have AM0 or AM1 illumination levels); so is the entire curve getting shifted downward for Tabby’s star, or it is only a range of wavelengths in visible?
Also, can we be fully sure about the accuracy of the data from 1890s to 1990s on 20% reduction in brightness?
@ A. Norman
I think your near perfect efficiency idea would be an excellent argument in many of these discussions. I’m not sure it is a good argument in this one. It’s hard to see why it wouldn’t be easier to block more sunlight, rather than go from 70 to 99 percent efficiency.
Keep that argument though, I think it is valid for the whole artifact search question in general.
I’m with the persons who think it is some intervening object. A gas/dust cloud captured into a distant orbit, or simply passing by close to the star (in interstellar terms).
If you happen to catch the process early on, you will first see gradual dimming as the density and thickness of the cloud in our line of sight increases. As it progresses across our line of sight, the internal structure of the cloud will result in short-term dips in brightness.
The cloud has to be in a distant enough orbit to remain cool of course.
@Larry Kennedy
“It’s hard to see why it wouldn’t be easier to block more sunlight, rather than go from 70 to 99 percent efficiency.”
Perhaps the limiting factor is the total quantity of available mass to build these structures. In which case going from 70% energy efficiency to 99% energy efficiency would be worth it, even if it requires several percent greater mass per unit area.
I thought KIC 8462852 might be in a hydrogen flow. The star system is in a cloud of hydrogen moving in our direction. The more hydrogen between earth and KIC 8462852 the dip in light continues to experience a constant rate of fading. The large fluctuations are hydrogen shadows caused by KIC 8462852 and it’s planets scooping hydrogen.
Andrew_W:
The dips Kepler saw took between 1 and 7 days to go down then up, or about 2-15 times as long as something at 1 AU. Since orbital speed drops as the square root of the orbital distance, just like temperature does, this implies temperatures 2-15 times lower than on Earth, or 20-150 K.
The above calculation is just a rough order of magnitude calculation to show that the occulters could be very cold. The material must be “very close” to the star compared to the distance between the star and the Earth, but could be on very wide orbits compared to an astronomical unit.
Marshall and Larry:
Good point about creating anti-matter; if for some reason it’s easier to make anti-matter from starlight than regular matter (like we do in particle accelerators and nuclear reactors) then anti-matter would be a great way to store stellar energy for future use.
The Schaefer paper includes two comparison stars.
One of these stars shows a slight dimming while the other shows a slight brightening over the Century 1890-1989.
However, these variations (using a rough trend analysis) are around .017 and .023 magnitude per century, almost within the error range of the 5-year bins.
KIC 8462852 is showing a dimming of around 0.165 (or 0.193) in magnitude nearly ten times that of the comparison stars. So we can be reasonably confident that we have a real dimming occurring in a relatively short time frame (astronomically speaking).
What is not made clear in the paper is that there appears to be some large movements in magnitude (1892-1917 and 1947-67) and then periods of apparent stability (1917-1947 and 1967-77).
I do not think we are looking at a linear stable trend in dimming but rather a dynamic variation in magnitude. A cloud of matter passing in front of KIC 8462852 would be an unlikely cause of a dynamic non-linear dimming over the past century unless it had a “ring” structure.
It may be helpful if the full set of magnitude measurements were publicly available to ensure that the 5-year bins are not producing or masking variations/trends.
IR searches have so far not turned up anything that looks like waste heat, but are they searching the right spectrum? A civilization hungry enough for energy that it would harvest a significant fraction of a star’s light might think it worthwhile to scavenge energy through secondary generation: take ~300K thermal energy and use that for an energy cycle that emits waste heat in the <50K range.
Jason Wright January 18, 2016 at 10:49
“Starlight” is a bit misleading, because I’m talking about collectors in close orbit about an F3 sun. What I’m imagining is a collector somewhat like our x-ray and gamma-ray telescopes, where you have surfaces at grazing angles to the incoming radiation – and you have a whole spectrum of high energy radiation coming from the star – and those surfaces direct the energy onto a target. This would be similar to how we create antimatter with accelerators, but they would be taking advantage of the hard radiation naturally produced by the star. We could probably do this today. They could have many such collectors, perhaps tens or hundreds of kilometers across, in orbit around the star as close as practical for the materials involved so as to get the most energy per unit area. They collect the antimatter particles that are created and contain them, discard the ordinary matter produced, and have a robotic vehicle come periodically to collect full containers of antimatter and swap in empty containers. They take a few containers of antimatter home to run their power grid, and the rest goes to their starship construction site to fuel the exploration vessels. So collectors like these might account for some or all of the long-term dimming if they were installed over a century or more.
In addition, there could be larger panels in more distant orbits used for some other purpose such as habitation, e.g., building a “ring world” or a habitable Dyson swarm. So there could be swarms of panels at different distances from the star, in different orbital inclinations, and different sizes, for different purposes, installed over a long period of time. All might contribute to the long-term dimming.
As for the two sets of very deep brightness dips, I’m imagining material being ferried from their construction site to the staging area from which the panels would be moved into their final locations, which could be in the star’s ecliptic plane, which is about 68 degrees to our line of sight, or so I’ve heard. The movement between the star and earth would just be a coincidence. (Remember that there is a nearby red dwarf star, and any “aliens” may originate there, not on a planet around the F3 star, and may be taking advantage of the close proximity to colonize this star and tap its energy, so they may be moving from the red dwarf to the F3 star from out of the F3 star’s ecliptic plane.) The problem with this idea is that pre-fabricated panels would be “stacked”, not spread out across a huge area, so this really isn’t a good explanation. And if we see more large dips that match the 700 day separation of the other two sets, then we have something in orbit around the F3 star and this explanation is unlikely.
Anyway, that’s my little sci-fi scenario, for what it’s worth.
How confident is anyone in the distance of this star? If it has been dimming for over a century, we have no idea what it’s intrinsic luminosity is which, as I understand it, is the basis for calculating distance. Someone mentioned this in the comments earlier, but I haven’t seen a response.
“What is not made clear in the paper is that there appears to be some large movements in magnitude (1892-1917 and 1947-67) and then periods of apparent stability (1917-1947 and 1967-77).”
When I looked at the chart, I noticed the large drop in brightness around 1900, but the two check stars also seemed to drop. I think this may be a difference in the sensitivity of the plate, or perhaps a shorter exposure. Brad Schaffer mentioned this period on the Wowsignal Podcast, and he said he doesn’t have high confidence about that part of the chart.
Larry, F4 stars emit hardly any photons capable of pair production, so I don’t know how you get antimatter from them. You need grazing incidence like you are describing for X rays and gamma rays, which F4 stars do not produce much of (there are some X rays from the corona, but they are nowhere near energetic enough to produce positrons, much less the antiprotons you need for charge neutrality).
Of course, we don’t know how they might do it, or what technology unknown to us they could use to convert starlight to antimatter, but your scenario seems overspecified to me.
@ Bill “even if it requires several percent greater mass per unit area.”
A good answer if true, however my expectation is that it would require more like several hundred percent.
Can they see the little red dwarf near by in the older plates, if they can they could see if it passed close to KIC 8462852 in the past. If it did potentially the result is a disturbance of one or both systems comet clouds, but they would need an enormous number as stated in the article. Perhaps the red dwarf piled up material in front of the stars line of sight resulting in the dimming of the century. Certainly an intriguing find that is for sure.
How about high quality hemispherical reflectors concentrating energy back at communities well away from the star? By geometry they would also be reflecting waste heat back again. Perhaps a secondary reflector behind the community concentrates the energy onto the actual collectors. Any time we would have line of site to the actual collectors they would be at such an angle to limit the emitting area. For a century of so there could be a steady build up of communities, followed by a new era of larger reflectors perhaps beaming right out of the system. This make any sense?
Jason Wright, thanks for your reply. What you’re saying appears to be somewhat at odds with how Dr. Bradley Schaefer sees the IR issue, in this pod-cast he picks a debris disc as his favorite explanation, but hasn’t been able to come up with an architecture for the disc that explain the lack of IR excess.
It certainly sounds to me like he sees the objects transiting speed as faster than you do and thinks the long total transit times as a product of their size, not their speed.
http://www.wowsignalpodcast.com/2016/01/season-3-episode-3-slow-and-fast.html
This star puts out a substantial amount of U.V in a region where plants can photosynthesis and also at wavelengths that enable photo dissociation to occur more readily. If this U.V interacts with water this could produce more O2 in an atmosphere perhaps allowing for the emergence of complex life earlier than on Earth. My big issue with advanced aliens around this star is the stars age, F type star have lower life spans than G types.
Could photo dissociation be occurring in the space around the star where light is absorbed and no recombination occurs as the material is blown out of the system by light and stellar wind pressures? Maybe a water moon is been boiled away.
Andrew_W:
The tradeoffs between size and speed with respect to the lack of IR emission are discussed in detail in Boyajian’s original paper. My estimates for orbital speed were rough order of magnitude estimates, subject to certain assumptions. Dr. Schaefer has a different preferred set of assumptions. But since neither of us has a self-consistent model for what’s going on at this point, it’s not surprising that we are taking different things as given and ignoring different pieces of the puzzle for now. I don’t think we disagree about the observational constraints, though.
Do we have a current (2015) measure of the apparent magnitude for KIC 8462852 comparable to the long term (1890-1989) data?
Would love to know if the dimming has continued in the period 1989-2015 or has it stabilised?
This star is in the Tycho2 catalog (which means, incidentally, that it should be included with a good mas-accuracy parallax in the Tycho – Gaia Astrometric Catalog to be released this summer) with a proper motion of 14 mas/yr (a very reasonable 31.5 km/sec at the current 1500 lyr distance estimate).
At that transverse velocity, the star would move 600 AU in a century, so that means if it was passing behind a cloud of some sort, that cloud would have to be much less than a light year in size (maybe 6000 AU across). That is a lot smaller than the typical clouds we see in (say) the Orion nebula; I would rate it as improbable, but probably not as improbable as the Alien Engineering Hypothesis, so it should be considered as a possibility. Maybe there are a lot of such clouds around, and we just don’t see then as there are none close to us.
@ Jason Wright In an earlier post you alluded to a band of cold material being your favorite explanation for what we’re seeing at Tabby’s star. I’m curious to hear a more detailed explanation, if you have the time.
Also, how has these most recent data affected your thoughts about the ETI hypothesis? Do you think it’s more likely, less likely, unchanged?
If we expect an IR excess from debris in orbit causing the dips, wouldn’t we expect a far larger IR excess from the debris that would be required to cause the 20% dimming over a century? Don’t the two effects when combined require the obscuring matter to be further out from the star, yet still including clumps with relatively quick transit times?
If so, back to the hypothesis that there’s a dark companion with it’s own dusty planetesimal system between us and KIC 8462852, that system making a centuries long transit.
I don’t fully understand the claim that no F3 stars exhibit these dimmings, when we didn’t know about the long term dimming of KIC 8462852 until Dr Schaefer minutely examined the Harvard plates. Maybe if we subjected all F3 stars to similar scrutiny we would find instances of dimming in some of those cases?
So quick and large a drop in intrinsic brightness in a main sequence star would not only be unprecedented but would contradict our understanding of astrophysics and stellar evolution.
Highly doubt that an advanced civilization capable of D sphere, would have waste heat energy issues, hence lack of IR fingerprint.
@Bilal Gicvan January 14, 2016 at 16:08
Just how many billion square kilometers of surface area we talking about here. I would think it would take ten thousand years..
Self replicating machine-structures = exponential growth, start with enough of these and time is no issue (and only considering out of this world reasoning).
@ hamilton1 – Excellent point, and exactly why I think that the DASCH team is probably going to apply this scrutiny to every star in their catalog.
@ Andrew_W – I don’t think the Kepler dips imply an substantial IR excess (there would be one, but lost in the noise from here on Earth). However, I would expect that there would be a substantial IR flux as a consequence of a 20% decline in visual flux over a century, and that is something we should be able to see today.
@ Rafik – If this star is included in the Tycho-Gaia astrometric solution (TGAS) scheduled for release this summer (as it should be given that it is the Tycho-2 catalog), then it will be possible to compare a Gaia magnitude estimate from 2015-2016 with a Tycho magnitude estimate from 1989-1993, both being space-based magnitude estimates. Not only that, but a similar comparison could be done for every one of the 2.5 million stars contained in the Tycho-2 catalogue. See
http://www.cosmos.esa.int/web/gaia/iow_20150115 for more on TGAS.
We have no IR signature.
If there were a natural body blocking the light it would generate IR.
So if the light dips are caused by a blocking body, it most probaby is not of natural origin.
So the lack of IR signature actually plays in favor of D sphere.
Any other stars from this civilization would probably be very dim by now.
Unless they have Clarke-level technology, any conceivable civilization is going to give off waste heat.
Here’s a crazy idea: what is the metallicity of the star? If it’s anomalously poor of metal, maybe it’s being mined for solids to build the solar collectors and heat radiators out of!
When it comes to waste heat, we should take into account that an advanced alien civilization could for various reasons to be reluctant to announce its existence and would take extra precautions to hide its signature.
We might think that a project of this scale would be easily observable to any other high-level civilization, but lets remember that the anomaly on the star was picked up by human observers and missed by computer programs.
The star’s oddity comes up only when under direct scrutiny of a sentient mind, which might also point at problem with our own SETI programs. The more data we get, the less contact actual people have with it and computer programs can have some very wide holes in their nets, as this star shows.
I agree, I’m interested in exotic possibilities too. I don’t mean to sound like a naysayer.
I guess the issue is that outside of science, people often get carried away with pseudoscience and wild theories without “doing their homework” eg Zecharia Sitchin (r.i.p.). Within science, there may be the opposite problem of ridiculing anything that seems “beyond the pale”. This is also a bad attitude, especially considering that exoplanets were once doubted and are now found in abundance.
Personally I believe there is ETI, but simpler life is much more common in the universe.
Marshall Eubanks
“it will be possible to compare a Gaia magnitude estimate from 2015-2016 with a Tycho magnitude estimate from 1989-1993, both being space-based magnitude estimates. Not only that, but a similar comparison could be done for every one of the 2.5 million stars contained in the Tycho-2 catalogue. See
http://www.cosmos.esa.int/web/gaia/iow_20150115 for more on TGAS.”
I think this should be one of the priorities. I asked earlier if it is possible to create a software looking for similar pattern in other stars using the Harvard plates as well.
As to above proposal it would be very beneficial, either as detection of new natural phenomena or SETI search.
“Tom Pliska January 18, 2016 at 19:17
Any other stars from this civilization would probably be very dim by now.”
Tom, Dyson Sphere candidates are nothing new(I know I repeat myself) but this one is very well covered by media due to the fact that it is difficult to explain by natural process. For example of other candidates see:
http://home.fnal.gov/~carrigan/infrared_astronomy/Fermilab_search.htm
It would be interesting to search for similar patterns in other stars using archive data we have.
Gfgh: If the cloud is distant enough from the star surely it will remain cool enough to be undetected in the IR observational bands?
Marshal Eubanks: several months back there was publicity about an Earth-mass cloud passing the central black hole of our galaxy. I don’t recall the physical size but I do remember it being referred to as planetary mass. In other words, small clouds do exist.
Marshall Eubanks
“it will be possible to compare a Gaia magnitude estimate from 2015-2016 with a Tycho magnitude estimate from 1989-1993, both being space-based magnitude estimates.”
That is great news – we will then know if the 1890-1989 dimming disappeared, stabilised, continued or accelerated.
Just wondering if it would be possible to produce “Harvard equivalent” glass plates on any scopes within the next year as a consistency check.
Forgive my ignorance but does anyone in the world still use glass plates? (amateurs??)
I would be very interested if the raw data from the Schaefer study could be made available to check if the 5-year bins are producing or masking artefacts/trends in variations in magnitude.
@kzb:
There is this object named G2 that was initially reported to be a cloud of some form. Turns out it seems to be a compact object that hasn’t stretched despite the brutal tidal forces it’s experiencing. G2 is most likely a young star with a massive core that is still accreting material. The black hole itself has not yet shown any increase in activity, and G2 survived its closest approach.
http://www.eso.org/public/news/eso1512/
Previously, in 2011 they reported on G2 as well
http://www.eso.org/public/news/eso1151/
According to Schaeffer, the Alien Megastructure” scenario took just as big a hit as the “comet” scenario with his new data. His line of thinking is that NO aliens, no matter HOW advanced, could build a megastructure FAST enough to dim a star by 20% in just 100 years. My response to this is that it all depends on the START POINT of the construction project! He would be right if construction had STARTED in 1890. BUT: If it started 100,00 years ago and 50% of the star’s light was ALREADY BLOCKED by 1890, invoking Moore’s Law AND Von Neumann machines, it would take LESS THAN ONE MILLENIUM to COMPLETE the project and block the remainder of the star’s light. This, AND Jason Wright’s above comments on heat re-radiation of an alien megastructure, COMBINED with RUMERS of a HINT of “reddening” in the system(which, IF CONFIRMED, would ALL BUT ELIMINATE an INTERNAL CAUSE of the dimming) ALL ADVANCE the “Alien Megastructure” scenario to one of ONLY A FEW FINAL OPTIONS(the most PROMISING ONE RIGHT NOW being the M dwarf companion “glancing blow” IMPACTOR scenario) left!
Several people have expressed a desire for the Harvary raw data. It is in fact available through the DASCH Lightcurve access webpage:
http://dasch.rc.fas.harvard.edu/lightcurve.php
Enter the coordinates of KIC 8462852: 20 06 15.457 +44 27 24.61
then click on the “download all points in table form” link when it is generated (takes 10 or 15 seconds to process)
then choose whatever format you want (I chose option A)
I then imported the data to a spreadsheet.
I don’t understand how is hard to consider building a Dsphere in 100 years timeframe.
Self replicating Von Neumann machines have exponential growth, seed enough of these and no time frame issues. Even more so if considering those machines could be nano scale and fast replicating cycle. Or considering not material but energy field structures harvesting the star.
Anyhow any kind of timeframe on building a Dsphere would not pass the Occam’s razor given the hudge number of assumptions in play.
Either way, if its a of natural or artificial origin, we should learn a lot from this!
“Just wondering if it would be possible to produce “Harvard equivalent” glass plates on any scopes within the next year as a consistency check.
Forgive my ignorance but does anyone in the world still use glass plates? (amateurs??) ”
Surprisingly I found a lot of archives with glass plates. I believe Schaefer mentioned a German observatory(Sonnenberg?) that has extensive collection.
Personally I also found:
Hamburg Uni archive from 26/27-02-38 to 10/11-10-61
http://www.hs.uni-hamburg.de/DE/Oef/Plattenarchiv/Plattendaten_VO_table.html
I found an interesting list of all major plate libraries that are being digitized
(see page 13), it seems there are huge collections.
http://cordis.europa.eu/pub/fp7/ict/docs/digicult/kounchev_en.pdf
This whole fantastic discussion seems to have come about from this:
(my emphasis)
I have to ask, though: How exactly does the slow dimming rule out the comet explanation for the short dips? The “Ockham’s razor” explanation in Schaefer’s abstract is contrived, I think. It depends much on how often you would find similar dimming if you analyzed a thousand random stars. My guess is you would find similar dimming (false or true positives, it does not matter) fairly often, at a 0.1-1% level, perhaps. If so, there really does not need to be any link between the two phenomena.
As to what it really is, let’s narrow it down:
1) It passes fast and (relatively) often, and only across this one star, so it has to be close to the star
2) The amount of occultation is much too large for a solid body, so it has to be a cloud of some kind.
3) There is no excess IR, so it has to be a localized, small cloud, rather than an entire disk of some sort.
The comet hypothesis fits all these just fine. Bodman & Quillen have published an analysis (http://arxiv.org/pdf/1511.08821v1.pdf) that shows that the gas and dust clouds of a few hundred ordinary-sized comets could well account for the amount of occultation seen, and it seems quite plausible that such a swarm of comets could be the result of the break-up of a larger body, recent or maybe not so recent.
To me, all that fits fairly well. The current frenzy in outlandish explanations seems to be motivated by wishful thinking and enabled by the overeager acceptance of the notion that 1) the long term dimming must be caused by the same thing as the occultations, and 2) the long term dimming cannot be caused by comets, ergo 3) comets do not cause the occultations. Unfortunately, 1) is far from convincing, making the argument moot.
Am I wrong?