This is an update in my continuing coverage of the mysterious, very mysterious, star KIC
8462852 or Boyajian's star for August 30, 2017.
The two rumored papers did indeed come out, and there are some interesting developments
in them, but as I said in my last update we would either end up moving towards solving
this, or we would head back off into mystery land.
Well, we have soundly wandered back off into mystery land.
There are now serious problems for every explanation on the table.
Everything advanced continues to have one flaw or another, including the alien megastructure
hypothesis, which is still on the table but not a good fit either.
Particularly, the question of the long-term dimming trend is most definitely deepening.
The first paper is by Josh Simon and colleagues, links to all papers mentioned in the description
below, and what they did was they took data collected by the All Sky Automated Survey
for Supernovae and the All Sky Automated Survey and were able to reconstruct what KIC 8462852
has been doing from 2006 to the present.
They found further evidence of the long-term trend and have found that the star is now
1.5 percent fainter now than it was in February of 2015.
But there's something new here, they found that the star also went through periods of
significant brightening meaning that the long-term trend goes both ways and is now better described
as long-term variability, though it's really not all that long-term since activity seems
to happen very rapidly on human timescales with this star.
Essentially, both surveys showed that over the last two years the star dimmed.
But in 2014, the star brightened.
During 2009 through 2013 it faded, but they found evidence that in 2006 it brightened.
Messy.
This is a problem for many of the explanations, but specifically the hypothesis that it recently
ate a planet.
It would essentially need to be actively consuming the displaced moons of that planet causing
brightening periods all while calming down over all after eating the planet itself.
That's possible, but the odds are bad for just happening to catch that in progress,
especially with an apparently mature star system like KIC 8462852.
But, then again, lottery odds are bad, but nevertheless people do win the lottery and
it's becoming increasingly clear that whatever is responsible for the behavior of this star
doesn't happen every day.
The authors move on to stellar activity, sun spots, etc.
The problem there is how deep the dips were.
Remember, this star's brightness during the Kepler run dropped as much as 22 percent.
That's some serious sunspot activity, but possible.
The other problem there is that okay, huge sunspots, but you also have to account for
how fast these dips occur.
The recent skara brae dip seems to have had a deep dip happen and recover on the order
of several hours.
In short, sun spots are not impossible, but not a good explanation, much like all the
other explanations.
The next explanation to take a hit is material in the interstellar medium, essentially cold
dust floating past within our line of sight to the star.
This was a convenient explanation that accounted for the lack of infrared emissions at this
star, usually dust clouds in orbit of a star warm up and radiate brightly in infrared.
Tabby's star does not, so logically the dust has to be cold.
Well, deep space is cold.
Further, clumpy dust, on its face, can potentially explain both the short-term and long-term
dips and general behavior of the star.
But only on its face.
The second paper by F. Meng and colleagues throws a wrench here, so much so that the
idea of dust in the interstellar medium didn't just take a beating, it's probably dead.
In their paper, they continue the study of the long-term dimming as well.
They saw it too, so any explanation put forth from now on is going to have to account for
it too, or will appear contrived.
They found that the dimming is less in infrared than it is in visible and ultraviolet light.
This is the first I've heard of any infrared at this star, but it does pin down that whatever
is obscuring the star is very small, as in tiny grains of dust.
They took a look at how that dust reddens the light from the star and they found that
dust in the interstellar medium doesn't fit the bill and go on to conclude that the
dust is not of normal interstellar origin.
They also mention the possibility of the dust being in our own Oort cloud, but note that
this suffers from an observational problem.
If the dust is close to us, then you'd see evidence of earth's motion as it orbits
the sun in the data.
We don't and adding that to a lack of dimming in any other stars that appear near KIC 8462852
and that makes Oort cloud material unlikely.
So the team concludes in the paper that whatever is causing the dimming at this star, is local
to that star, probably circumstellar material of some sort that's made up of very small
particulate matter, in other words dust but where's all the infrared?
And that brings us back full circle to 2016 and the possibility of cold comets entering
the system, perhaps perturbed by a red dwarf near KIC 8462852.
The paper mentions the cold comet hypothesis again from the original Boyajian and colleagues
paper.
The problem here is that we have two other existing papers that already deal blows to
this hypothesis.
The first is Bradley Schaeffer's discovery of the long-term dimming trend in which he
calculated that you'd need a whole lot of very huge comets for this effect, on order
of 640,000.
Given the two new confirmations of the long-term trend, or long term variability, this view
seems vindicated.
The second is the new paper by S. Rappaport that I covered in my last update which points
out that exocomets seem to have very unique and recognizable shark tooth-like signatures
in the Kepler light curves, and really do not resemble what's happening at KIC 8462852.
In short, we still have no real clue what's going on with this star though it probably
involves very small grains of something one way or another that cause a lot of long-term
variability in the star's brightness, but also can dip the stars light very rapidly.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently wondering if the
Tabby's Star extraterrestrials are just messing with us and sitting in their megastructures
snickering as they dump out dust to confuse everyone.
I wish they'd stop it and be sure to check out my books at your favorite online book
retailer and subscribe to my channel for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.
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