And not all of the light that interacts with the coma passes through or is reflected. Some of that light -- a significant portion, in fact -- is absorbed and drives chemical reactions. For instance, when Solar ultraviolet light breaks down the gas molecules, causing them to glow. That is a form of fluorescence, a process that doesn't actually produce an INCREASE in luminosity except under very specific conditions.
Although, the idea that the crystals in a comet's tail could be used as the gain medium in a gigantic solar-flare-pumped x-ray laser definitely appeals to my inner trekkie...
Chemical reactions that freeze instantly due to the extreme cold of space compared to the extremely warmer climate that the clouds on Earth are part of.
My recent response from Brad Schaefer.
Hi;
Yes, I totally agree with you. And as part of all this, we gotta consider all the possibilities, because there might be loopholes that Nature might have slipped through with. You pointed out two great reasons as to why the comets could not last 'long'; the comets will be evaporated and that other planets in the system would perturb the orbits of the comet family out of their tight grouping. Yes. Both of these mechanisms take perhaps centuries or millennia to work, depending critically on what the orbits actually are. So a loophole would be if the comet family was recently formed, say within the last orbit or within the last few years. Perhaps some poor super-giant-comet (say, like a large Kuiper Belt Object) randomly got hit and broken up back in 1982, and on its usual orbit the now-cluster of comet fragments is emitting enough dust (from the breakup) that when it passes in front of the star we see a dimming. Well, this has a lot of problems too. Well, this is the sort of logic (seeking loopholes, or seeking some sub-scenario) that might work.
Hmmm, but it still dips and dims. But you and I have refutations for all proposals on the table, including the extreme-speculation idea. So *something* is going on, and we have not spotted it yet.
And that is why casting around for ideas is important. I'm thinking that there are only two types of solutions. The first is that there is some hidden loophole to one of our 'refutations', and Nature has quietly slipped into that loophole. The second is that there is some new fresh idea not yet thought of.
So let me propose a good likely means to make a big advance: We should get a spectrum of the star *during* a dip. From the spectrum, we might see absorption lines from any gas associated with the 'occulter', we might see a reddening that would point to the occulter being mainly dust, or we might see a color neutral dip that would point to a solid body. Thus, a spectrum would tell us the nature of the occulter, and this would greatly narrow down models. But dips in the KIC 8462852 light curve are uncommon, so we have to await the next big dip. Also importantly, we have to have some sort of an alert system to know when the star is undergoing one of its day-long dips. So someone has to keep monitorring the star, hour-by-hour, waiting for it to dip, then alert observers with spectrometers on big telescopes, and then they can get the spectra during a dip. Tabby Boyajian is leading a group of observers from the American Association of Variable Stars Observers (AAVSO) who are keeping the star under nearly continuous monitorring. These observers are worldwide and they are great, and they are of professional quality. Tabby also has lined up big scopes to fast switch over to her star whenever a dip is found. (This includes the Swift spacecraft.) Alas, so far, there have been no dips. But they will come sometime, and we'll get a spectrum in a dip, and learn the nature of the occulter.