So if there was a Dyson sphere being constructed some 1,400 years ago, wouldn't there be some much greater probability of seeing such a thing in our neighborhood some 1,400 years later? (Queue the Fermi paradox comment...)
We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an \AA ngstr\"om absorption coefficient of 2.19±0.45, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15 μm. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.
We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.
Two papers have been published on Arxiv ahead of tomorrow's press embargo.The data supports, but does not prove Dust - which requires constant replenishment, as the dust particles are so small that they'd be depleted by the stellar wind around KIC 8462852 in a matter of days. A source for such a supply of dust remains unknown. Gasses appear to be absent from the dust.
Regarding the absence of spectral features: I don't think is says very much about the gas content. I wouldn't expect much of a spectral signal from such small dips anyway.
Quote from: as58 on 01/03/2018 05:00 amRegarding the absence of spectral features: I don't think is says very much about the gas content. I wouldn't expect much of a spectral signal from such small dips anyway.Citing Crimfants on Reddit for that bit on gas. I can't see Jason Wright's entry that says as such.
These papers certainly don’t seem to rule out Bruce Gary’s explanation.
Quote from: Star One on 01/03/2018 10:17 amThese papers certainly don’t seem to rule out Bruce Gary’s explanation.I'm not sure it eliminates any ideas that weren't already out of the running for the past year or two, but now it's official, cite-able, and it does put some better constraints on what the final explanation is going to look like.
Someone I saw online claimed it doesn’t even rule out asteroid mining!!!
Quote from: RotoSequence on 01/03/2018 11:02 amQuote from: Star One on 01/03/2018 10:17 amThese papers certainly don’t seem to rule out Bruce Gary’s explanation.I'm not sure it eliminates any ideas that weren't already out of the running for the past year or two, but now it's official, cite-able, and it does put some better constraints on what the final explanation is going to look like. Someone I saw online claimed it doesn’t even rule out asteroid mining!!!
Quote from: Star One on 01/03/2018 11:25 amQuote from: RotoSequence on 01/03/2018 11:02 amQuote from: Star One on 01/03/2018 10:17 amThese papers certainly don’t seem to rule out Bruce Gary’s explanation.I'm not sure it eliminates any ideas that weren't already out of the running for the past year or two, but now it's official, cite-able, and it does put some better constraints on what the final explanation is going to look like. Someone I saw online claimed it doesn’t even rule out asteroid mining!!!Yep, I'm glad to see some progress in explaining it all, but I still find it extremely easy to invoke ETI to still be consistent with what has been learned. Even ETI's might make a bit of pollution while making their structures. See how easy that was!
I wonder if these papers have taken us as far as we can go in the study of this star with our current technology. That the unknowns will have to remain until better technology is available for its study.
Quote from: Star One on 01/03/2018 03:02 pmI wonder if these papers have taken us as far as we can go in the study of this star with our current technology. That the unknowns will have to remain until better technology is available for its study.No. If there's another dip, there is plenty we can still learn (e.g. ruling in/out some of the proposed periodicities), especially if there's a deep one.--- Tony
Yep, I'm glad to see some progress in explaining it all, but I still find it extremely easy to invoke ETI to still be consistent with what has been learned. Even ETI's might make a bit of pollution while making their structures. See how easy that was!
Quote from: Stan-1967 on 01/03/2018 02:12 pmYep, I'm glad to see some progress in explaining it all, but I still find it extremely easy to invoke ETI to still be consistent with what has been learned. Even ETI's might make a bit of pollution while making their structures. See how easy that was! I think they are doing a good job of chasing those aliens away! When the dips were first noticed once of the causes that fit the data back then was an optically thick and cold object. Which would have been weird. That scenario fit with some proposed ETI explanations. We now know that it is dust that is causing the dips and not something else so we can rule out some of the initially proposed ETI scenarios. The data thus far is inconsistent with a Dyson sphere, ring, or swarm being the cause of these latest dips. Something is generating dust and there doesn't appear to be anything yet observed that would favor an artificial source for it over a natural source. Also if I had a giant energy collecting structure I wouldn't want dust anywhere near it!
Quote from: jebbo on 01/03/2018 03:18 pmQuote from: Star One on 01/03/2018 03:02 pmI wonder if these papers have taken us as far as we can go in the study of this star with our current technology. That the unknowns will have to remain until better technology is available for its study.No. If there's another dip, there is plenty we can still learn (e.g. ruling in/out some of the proposed periodicities), especially if there's a deep one.--- TonyAren't we still in the phase of looking at this star with smaller telescopes until we know when the next event will come? The more expensive telescopes should be able to say significantly more, or at least with significantly more certainty, about the big dips, the periods with smaller dips, the brightening events and whether there is any relation with a long term evolution. We could still be years away from knowing when to point the big boys towards this star.