This is an update in my continuing coverage of the mysterious star KIC 8462852 or Tabby’s
star for December of 2021.
Yet again, things have taken a turn for the mysterious with this star and the circumstances
surrounding it.
But before we get to that, here’s what the star has been doing lately in a nutshell.
Last month the star changed behaviour somewhat and seemingly went into a sustained 1 percent
dimming period.
This is not characteristic of the star, it generally exhibits short term, but often very
deep dips.
For example in the Kepler data, the dips reached as much as 22 percent, but tended to only
last for a few days or so.
Instead here, we’ve had a sustained plus or minus 1 percent dip that’s lasted nearly
a month, that also shows very brief periods of recovery, in a way it’s doing almost
the opposite mirror image of what it usually does.
This one percent dimming is noteworthy in another way, it’s rather shallow.
The dips in the star's brightness since it’s been observed after the Kepler mission tend
towards weaker and weaker dimming events.
This might be consistent with a collisional model, such as colliding cold comets as was
first advanced by Dr. Boyajian in the early days of this story.
The problem is that you need an implausibly high number of comets to do this, or effectively
a giant comet that might better be classed as a planet disintegrating.
But so far, no models of this nature have predicted exactly what’s observed with this
star.
Another noteworthy development with the current dimming is that one observer found that the
material obscuring the star during this dimming went optically thick for a time, basically
floating in and out of optical thickness.
This was found by observing different wavelengths of light, and if it actually is the case it
would indicate the dust cloud getting significantly thicker and thinner as it passed in front
of the star, but remained thick enough to keep the star visually dimmed.
Optical thickness can mean several things, including a huge solid object obscuring a
star such as a gigantic alien megastructure, but in this case it looks like the dust simply
went thick for a time, complicating models.
But, while unlikely, some kind of alien origin remains on the long shot table for this star,
and that’s something that’s deepened a bit, more on that later.
Point is, this star is behaving very strangely, even for a phenomenon of dust.
One particularly vexing aspect of this star is how the dust is hanging around in the system
at all.
The star exhibits a long term dimming trend, which is probably directly linked to the short
term dimming events.
After all, how likely is it that two separate but unusual phenomena would be happening with
the same star without being linked, especially when both involve dimming.
But this dust is known to be very small, through studies comparing different wavelengths of
light absorption during dips.
This is tiny sub micron stuff that should be continuously blown out of the system.
So whatever is happening seems to be replenishing the dust at a greater rate than its being
blown out, confounding collisional models.
On the other hand, the fact that the dips recently have become more shallow as compared
to when Kepler observed it tends to support a collisional model where things are dissipating.
Another development is that the dip seems to coincide with predictions of periodicity
put forth by Gary Sacco, who many of you know has been checking on this subject with his
collections of observations over on Event Horizon.
We’ll check in again with him soon, but the establishment of periodicity is very important
in figuring out what’s going on with this star.
Establishing periodicity would eliminate a lot of open questions, such as if this could
be some kind of phenomenon of interstellar dust and we’re just seeing this from line
of sight or if it is indeed in orbit around this star.
Interstellar dust is unlikely because if it were that, we should see it also affecting
nearby stars to KIC 8462852 from our line of sight.
A cloud at night does not cover just one star, it covers all nearby ones from your perspective.
Same with the galaxy.
This is not seen, and whatever is happening is only having an effect on this specific
point-like star system, suggesting that the dust around it is orbiting it.
Establishing this orbit is key, because if Sacco is right in his paper, link to all cited
papers below, then the dust blocking Tabby’s star is orbiting it within the star’s habitable
zone.
Evidence for this seems to be growing.
But that’s where it gets puzzling because dust like that, especially at the measured
size of the dust, which is a very tiny smoke-like material, should be warming in Infrared as
well as blowing out of the system.
No infrared emissions from this dust have been seen, and given the long term dimming
trend of over at least a century that’s present with this star, then some of it must
be hanging around and should be glowing with warmth.
It’s apparently not, but at least established periodicity will help in sorting this out,
and perhaps shedding light on whether the dust is truly cold.
The best natural hypothesis to explain the behaviour of the star is some kind of rather
odd collisional model, where cascades of material collide and create dust clouds.
But it’s hard to envision a method where this could do it continuously long term, remember,
strong evidence for dips in this star’s light have been found in past sky surveys
dating from the 1930’s to the 1970s’ in addition to Kepler’s observations and those
done since.
Whatever is going on is doing so continuously in some sort of prolonged process.
What that process is remains very much unclear.
And it may get even more unclear, and here’s where the star itself hasn’t thrown us another
curveball, but indeed the galaxy has.
In a paper by Edward Schmidt he details searches he’s done through past sky surveys to try
to find candidates behaving in a similar manner to KIC 8462852.
This is a natural thing to do, if you want to understand something it’s far better
to have multiple examples to study and compare than just a single one.
And he found no shortage of candidates, reported across two papers.
This is good news for characterizing Tabby’s star, because now those candidates can be
observed and monitored.
If they are indeed due to the same phenomenon, then observers will be able to collect a lot
more data on different candidates and get a much clearer picture of what could possibly
be going on with these stars.
Within this there is also the possibility of a smoking gun answer that settles it once
and for all, some clearer example of what dust in these systems is doing, what is creating
it, and so on.
This also goes for the alien option as well.
And that’s where this gets strange.
The new paper reports 15 new candidates for stars behaving like KIC 8462852.
Termed slow dippers, the light curves of these stars are very similar to Boyajian’s star,
but there’s something odd here.
Two apparent patterns have emerged in this data that do not appear to be random chance,
though more data and candidates are needed to go further with this.
The first is that the candidate stars seem to cluster.
And more they seem to cluster in the general area of KIC 8462852.
This is not what you would expect from a random distribution of stars.
It, oddly enough, is what you would expect from an expanding alien civilization, evoking
the ideas of potential mining operations being the culprit for the dust creation.
But one has to be careful here, because invoking alien civilizations comes with some severe
problems.
The biggest is aliens of the gaps thinking, where aliens can do just about anything, and
thus you can invoke them to explain away anything.
You need more to go on, and it just isn’t here yet with these stars.
But the clustering remains very odd.
Now naturally the next question to ask would be is the reason for the clustering superficial,
and that some intervening dust in the interstellar medium is causing the effect.
This isn’t the case because again because you’d see nearby stars also dimming and
experiencing the effect, and that is not seen.
So whatever it is, it’s going on directly around these stars, and there is no good reason
for the apparent clustering, if it indeed turns out to be real, which it seems to be.
But then we come to oddity number two.
Not only do the candidate stars cluster in space, but they also cluster in type on the
Herzprung-Russell diagram.
This is beyond weird, all of the stars are either Type F like Tabby’s star, or Type
G like the sun.
Giant stars and small stars do not seem to do this.
And this makes no sense on its face.
You’d think you’d see it happening with orange dwarfs and red dwarfs and all sorts
of stars.
But it may be that those types of stars somehow eliminate dust like this more efficiently
than Type F and G, but that’s just a shot in the dark.
But it is worth noting that obviously Type G stars are pretty good for life, we live
next to one, and Type F stars are a bit shorter lived, but pretty stable and while they may
not be ideal for life to form around, they might be just fine for aliens to colonize
and use.
But needless to say that this development is kinda spooky, clustering in space, and
clustering in stellar classification at the same time.
As a result, the paper suggests that these new candidates may make worthwhile candidates
for SETI to take a closer look at.
And indeed, they should be studied in general just to try to determine exactly what this
vexing phenomenon that happens to some stars, apparently selectively, is, whether natural
or otherwise.
And for fun, I’ll leave you with this.
For Northern Hemisphere observers, and those north enough to see them that know your constellations
or have a phone app that does, you can look at least in the general direction of these
stars and ponder what might be going on here.
Tabby’s star is located in the constellation Cygnus, sometimes known as the northern cross
or the swan.
The next constellation over is Lyra, marked by one of the night sky’s most famous and
brightest stars Vega, also of science fiction fame, that was the first star Jodie Foster
saw on her journey in Contact.
These candidate stars, while not naked eye visible, are clustered around the constellation
of Lyra, with Tabby’s star being just above the wing of the swan pointing towards Lyra.
See Vega, and you're in the right area.
Interesting indeed, and it’s something I do often when those constellations are in
the sky.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently musing about KIC
8462852 again.
Just when you think we’re getting a solid handle on what’s going on with it, you suddenly
find out you don’t.
That’s been the case for this star since 2015, and I have little doubt that there are
more surprises to come and be sure to check out my books at your favorite online book
retailer and subscribe to my channels for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.