So today we’ll be taking our first look
at Astronomical techniques and SETI, the Search for Extraterrestrial Intelligence, and I thought
we’d kick that off by looking at KIC 8462852, also known as Tabby’s Star. This star was one of many observed continuously
for years by the Kepler Space Observatory and it was noticed in late 2015 that there
was some very peculiar dips in its brightness that do not match up to phenomena we’ve
previously observed. Now while it is almost certainly a natural
phenomena, we never like to rule out the idea that strange things might be the results of
either errors or artificial tinkering, so it’s been suggested it could be a megastructure,
a type of very large artificial construct, presumably of alien origin. Now if you happen to already be familiar with
this channel it will come as no surprise I get asked about Tabby’s Star a lot. Two of the biggest subjects covered on this
channel are megastructures and the Fermi Paradox, the question of where all the aliens are. If you’re not familiar with these topics
you can click either of the links on the screen right now to pause this video and watch those
in new windows. You should also turn on the closed caption
subtitles if you’re not used to my voice yet. So I get asked about this star a lot and have
since it came out. I avoided doing a video on it because I didn’t
think it likely to be a megastructure… and I still do not… and in astronomy and physics
it isn’t unusual to encounter strange mysteries that defy obvious explanations and have to
wait years for the evidence to become available. It’s a bit tedious and frustrating but you
get used to it. I changed my mind both because I have been
getting asked about it a lot more recently and because we do have more information now,
but also because I don’t think anyone’s done a nice simple down to Earth explanation
of the situation. Stuff gets skipped for brevity that I think
is important to a basic understanding of this phenomena. We don’t do brevity on this channel, and
while we do aim for simplicity we do that not by skipping the hard stuff but by patiently
dissecting it into nice mouth-sized chewable bits for easy digestion. We’ll do that by dividing it into topics
for today and future videos, and here are out topics for today, our questions we want
to answer: 1) What is the Kepler Space Observatory? 2) How did Kepler help us find Exoplanets? 3) What was the anomaly it found at Tabby’s
Star 4) What does this information tell us? 5) What natural phenomena might explain this? 6) What new Info and developments have occurred? 7) What sort of Megastructure could it be? Now as mentioned we’ve covered both the
Fermi Paradox and Megastructures in detail elsewhere, so we’ll be skimming a lot of
that, this video will already be long enough you probably want to settle in with a cup
of coffee and snack; so if we covered those in detail again it would just be longer and
we’ve already spent several hours on each of those topics. Our first Topic is the Kepler Space Observatory,
this was launched in 2009 into orbit around the sun. It doesn’t orbit Earth but rather was launched
into orbit around the sun, initially trailing behind Earth and a bit further out and is
now over a hundred million miles away from us. It got further behind us in our orbit because
it is a bit further from the sun then us, and the further you are away from a star the
long an orbit takes, same as being closer to a star, or being around a more massive
star, makes those orbits go faster. Which is pretty important to exoplanet hunting,
but for the moment means Kepler is a long way behind us. Now what this observatory observes is pretty
straight-forward. It is a photometer, which means it measure
brightness. In this case Kepler constantly measures the
brightness of roughly 150,000 stars. Which sounds like a lot but it actually is
looking at the same patch of the sky and it’s a very small patch, about a quarter of a percent
of the night sky. That chunk incidentally is in between Vega
and Deneb. You probably know Deneb as the star that makes
up the tail of Cygnus the Swan, and Vega is in the constellation Lyra, both of which are
fairly close to the big and little dipper’s and North Star Polaris. In fact Vega was the North Star our ancestor
used when the Ice age was ending and will be again in a little over ten thousand years. Earth has a 26,000 year planetary precession
and at the moment that makes Polaris the North Star, Vega will get its turn again, and it’s
also where terms like the Age of Aquarius come from, since the Sun appears in the spring
Equinox of the Northern hemisphere in one of the zodiac constellations and that changes
every couple thousand years and right now it’s Aquarius. So Kepler tilts its eyes up and looks at that
patch of the sky year round, and it just watches for any increase or decrease in brightness
of those stars in that patch, which is again about 150,000. Many of these stars have other names or catalogues
numbers too but they exist in the Kepler Input Catalogue, or KIC. Kepler wasn’t looking for new stars it was
observing known ones but not many stars actually have names since there are so many of them
so it isn’t unusual for one to have multiple catalogue entries and just get referred to
by whichever one was used when the interesting thing about it was found, then it usually
gets a name to save time and confusion. There’s a lot of exoplanets and a lot of
them have names beginning with Kepler or Gliese and then a number and that name just tells
you the catalog, the Gliese catalog for instance is a catalog of nearby stars originally published
in 1957 by German Astronomer Wilhelm Gliese and it’s been kept up and unsurprisingly
a lot of those stars had no other name yet and were also the easiest to look for planets
around. Those will obviously need renaming if we ever
colonize them since a large number of our nearby stars are named Gliese something-or-other
and no colony is going to keep that name in abridged form since it would be like naming
your island Atlas or Rand-Mcnally. And there’s a handful of these catalogs
that almost all exoplanets are catalogued in. Which takes us to topic 2, hunting for Exoplanets. Stars dim for many reasons, ours fluctuates
in brightness and they all do, but a common cause is from an object getting in the way. And a pretty big object to cause a star to
noticeably dim. Or a pretty close object. Mercury blocks a lot more light than Mars
does for instance, even though it’s a bit smaller. Now to detect a planet this way you need three
things. First you need for its orbital plane to be
tilted toward us, you wouldn’t see Mercury or Earth blocking sunlight if you were hanging
over the Sun’s pole. So we can’t see an exoplanet around a star
that’s orbital plane is cocked away from us and that’s most of them. People tend to think solar systems line up
with the galactic plane but they mostly don’t, our own is tilted about 60 degrees off it. Second you need there to be a planet there
that’s big enough or close enough to its sun to block enough light for us to notice
it, that’s why virtually all the original exoplanets were huge things of a size with
Jupiter and close to their Sun, Hot Jupiters are just easiest to see The bigger it is,
the more light it blocks, but the closer it is the more light it blocks and the more likely
it is to be in between us and that star. A tiny little planet like Pluto far away from
its sun is very unlikely to line up with its star and an observer and is so small and far
away it blocks virtually no light. It’s also takes a long time to orbit, which
is the third thing. You need to stare at these stars for a long
time to not only see a dimming but also a repeat of that dimming. Earth would block light to an observer once
a year, Pluto would do it every couple of centuries, and until you’ve seen this periodic
dimming at least a couple times you can’t do much else. Once you’ve observed it at least twice,
preferably thrice, you can take that period and say there’s a planet there and it has
a an orbital period of so many days and from that, combined with the star’s mass, calculate
how far away it is from its own sun. You can then take that star’s brightness
and determine if that planet might be close enough to have liquid water on it instead
of ice but far enough not to be boiling. What we call the Habitable zone. If Earth were around a much more massive star,
but at the same distance, our year would be shorter, we’d also burn to death because
more massive stars are a lot brighter, a star twice as massive as our own isn’t twice
as bright, it’s more like ten times as bright. We also wouldn’t be around such a star anyway
since a star twice as massive as our own would only live a little over a billion years, our
sun is 4.6 billion years old, and the sun was a good 4 billions years old when the first
animals started emerging, and not complex ones either, the sea sponge is usually considered
to be the first animal. So we don’t just look for planets around
distant suns, we have after all found thousands of them in the last decade, we look for planets
in the Habitbale Zone of each system and Kepler’s method, which is just one of the exoplanet
hunting methods, is a pretty good one for those hunts. If for instance we detected a drop of a less
than percent in a star’s brightness for a day or so once every 750 day’s around
a star about half again our sun’s mass and about 5 times brighter we’d know there was
a reasonably Earth-sized planet hanging out about 1.8 Astronomical Units, AU, 1.8 times
further from its sun that Earth was, and that the planet in question would get about half-again
as much light as we do, in terms of sunlight per unit area… meaning it would be pretty
hot but maybe habitable. We wouldn’t much care about one blocking
more than a percent of that light because it would be too big to be a potentially habitable
planet and one blocking a lot more than a percent would presumably be huge. Indeed way too huge for even a gas giant if
it were orbiting that far out, and when you’re collecting data from 150,000 stars each day
for years at a time you’re not looking at that raw data you have a computer shuffling
it for the stuff you want. So that takes us to Topic 3, the anomaly around
Tabby’s Star. Because it is half again our sun’s mass
and about 5 times brighter than our sun. We’ve detected this anomaly twice, a dip
in brightness of 15% the first time and 22% the second time. The first was in March 2011 and the second
in February of 2013. With a spread of about 750 days. Kepler was launched in March 2009 so we just
missed a chance to see it then, and the observatory was having problem in April 2015 so we missed
that chance too. We get another in May of 2017. But the dip was huge, and not what was being
looked for, since it is most definitely not a Earth-sized Habitable Zone Planet. With that period it would be closer to Venus
than Earth in how much light it gets, and it would be a lot bigger than Jupiter. The second bigger dip was also very irregular,
dimming then very slightly brightening and dimming way more, something you might expect
off a double planet or a coincidental conjunction of two planets at the time it was transiting
its star for us. So nobody noticed it before the third occasion
would have happened and it was actually volunteers, citizen scientists they’ve been getting
called, who poured through the data manually in the Planet Hunters Project. Citizen scientist is a newer term, I would
just call that an amateur astronomer, and astronomy has relied on them for a long time,
but regardless I like the initiative to bring more folks into the hunt and crowdsourcing,
for both funds and volunteers, is starting to show up as a genuine alternative to either
government or big business research especially in things like SETI and astronomy in general
and I find this move both fascinating and potentially incredibly useful. I’ve some friends who started experimenting
with research through crowdsourcing for their Space Ranch Aquaponics project and it seems
quite promising. It’s something I think we’ll talk about
more in the future, both in regard to SETI and some other projects like that. Anyway, nobody saw it in time for the third
dip in Early 2015 or we could have arranged to look at it without Kepler which again was
malfunctioning at the time, but once they did they sent on to the astronomers who went
WTF, and nicknamed the Star the WTF star, which officially was short for Where’s the
Flux?, in reference to the weird flux in brightness, though I preferred What the Flux personally. Eventually instead of calling it by its Kepler
Catalogue number or that technically-not-a-curse-word cognomen everyone started calling it for the
lead author on the team that wrote it up, Astronomer Tabetha Boyajian, or Tabby’s
Star. She’s also led the campaign to get funds
to observe the star in more detail and in different frequencies then Kepler did. But that was the anomaly, and again we just
missed seeing it the first time in 2009 right before Kepler went active and missed it in
2015 from technical problems, so we haven’t got much data yet. So Topic #4, what does this tell us? First as I mentioned a dip of this magnitude
at that distance, a bit under twice as far from that Star as Earth is from our sun, means
the thing is huge, whatever it is. Much bigger than Jupiter. Second it’s hotter than Earth since it gets
about 50% more sunlight per unit area. Now I want to mention that Tabby’s Star
is a F3 Star either on the main sequence or the late stage of it as what we call a subgiant. It’s decently brighter than a main sequence
star of its mass should be. Not tons, not like an actual red giant, but
the assumption is this is an old star near the end of its life. That’s been challenged more recently but
we’ll get to that. Now old for a star of this mass would mean
creeping up on 3 billion years, and again our own sun is 4.6 billion years old. Obviously we’ll be talking about the alien
artifact option near the end but I want to drive that home now, this thing is around
a star that’s maximum lifetime would have caused it to die about the same time multi-cellular
life was just coming into existence on Earth, and the thing in question is pretty hot compared
to Earth so it’s not a great candidate for life to have originated. So Topic #5, what natural phenomena might
explain this, and why many of the suggested ones don’t work well. It’s too big to be a planet, but an object
doesn’t have to be massive to block a lot of light, anymore than your curtains have
to be heavier than a bowling ball just because they block more light. So the first couple thoughts were a lot of
gas and ice, like a comet, comets are very small but very bright after all and thus block
a lot light. Or alternatively maybe a collision of planets
that sprayed debris everywhere. Now remember we’ve only seen this twice,
so for instance a big comet coming in from deep space could have been spotted as it approached
and 750 days later as it left for instance. Ditto it could have been a whole wave of comets
perturbed in by some large body sweeping around in the outer solar system. Tabby’s Star does have a red dwarf star
about 800 AU from it, for relative comparison Pluto is about one twentieth that distance
at 40 AU, and Alpha Centuari is over 300 times further away at around a quarter of a million
AU from us. So that’s a very plausible source of the
sort of disruption that can cause a big deluge of comets. And debris spread outs but stay decently clumped
on timelines of a couple of years, again the first dip masked 15% of the star’s brightness
and the second time 22%, so an expanding wave of debris would work. Like that produced by two planets colliding. Such collision ought to be incredibly rare,
so that it would be weird to luck out and see one, but we don’t really know how rare
and it is the sort of thing you’d loosely guess happened every billion or so years and
expect the debris to hang around for decades. So watching 150,000 stars and seeing one is
improbable but not winning the lottery improbable. So of course they looked for evidence of either
of those. We can’t see the presumed conjunction of
it with the star and us till May 2017 but any big debris field ought to be scattering
light and it out to be emitting as much light as it absorbed. What it scattered and reflected plus what
it absorbed would equal what it blocked, and even comets which are quite reflective absorb
a lot of light. As we’ve talked about a lot on this channel,
especially in regard to Dyson Spheres and the concept of a Planet-Wide city, a Ecumenopolis,
light absorbed gets emitted as heat. In this case as infrared radiation in the
general zone of about 10 micron wavelengths, which corresponds to roughly Earth-like temperatures. Whatever hits an object in space and doesn’t
bounce away will warm that object until it reaches a temperature where it’s radiating
away as much as it absorbs, this equilibrium point has a peak frequency associated to it,
and distribution of wavelengths around it, that we can look for. Needless to say those wavelengths associated
to the temperatures liquid water can exist at interest us greatly when looking at places
where biological life might exist. We’d expect the debris to be glowing with
all that light and quite brightly as these things go. Indeed a planetary collision would glow a
lot hotter too, since there’s a lot of energy converted into heat in that sort of collision,
the kind we think made our own moon. You also wouldn’t expect an older star to
have as many big collisions around it, those get less common as time passes and debris
clumps together and either gets into a stable orbit, falls into the sun, or gets ejected
from the solar system. I’ve heard folks doubt the comet barrage
options because of how much would be needed but I’m inclined to reject that, even though
it really would need to be a huge amount in this case and I agree it isn’t terribly
satisfactory as answer. We don’t know how much ice is hanging out
in deep space near Earth but Oort Cloud estimates often routinely and largely exceeds Earth’s
own mass and an awful lot of that is ice, so it doesn’t seem that strange to me to
think this larger star might have even more than us and that having a red dwarf only 800
AU away might cause a massive disruption, heck it could be a small planet passing by
dragging a ton of stuff with it while it disintegrates, Pluto and most Icy Dwarfs are essentially
over-sized comets. But it doesn’t look terribly plausible either. A really big asteroid belt could work, asteroids
block more light per unit mass than planets do. So an Earth’s worth of asteroid’s in terms
of mass would block a lot more light than us. But you’d kinda expect something like that
to be decently symmetric, a ring, not a blob, and a ring doesn’t have an orbital period
making it block light every couple years for a couple days, it’s always blocking light
at that angle. But you could have a partial ring, a bit of
swarm of asteroids that moved in a pack, we see that with Trojan asteroid Fields for instance
and for that matter a big planet like Jupiter could have a really huge swarm of junk around
it, sort of like Saturn Rings, and it could be tilted like Uranus is so rings were perpendicular
to the ecliptic and blocked a lot light. So what’s left? Well a planet forming would work, a protoplanet. It’s not an ideal solution either particularly
since the star would have to presumably be a lot younger than it appears on initial inspection,
but dating stars is harder than it sounds like and we often do it by looking at the
stars nearby it that it’s moving with. That’s not always the same thing by the
way, stars often form from the same nebula and stick together in their movement through
the galaxy but many spin off and packs of stars often plow through other packs of stars. Some of the stars in our night sky have been
with us since the sun was born and others are just briefly passing by. When we can see many moving more or less together
it makes narrowing down their age a lot easier. But moving into newer developments, topic
6. We’re not sure how old this star is, but
if it is younger than we think a protoplanet might work. Now you can have planets form in star systems
that aren’t new, after all if two ram together and explode you’d expect some of that to
coalesce back into a new planet eventually, so we could have a clumping debris field that
already cooled in an older star system too, but neither of these feels too plausible either. We’ve also been looking at old photographic
plates of the star, again the catalogue name or calling it the WTF Star or tabby’s Star
are all very new, this thing was found over a century ago and well catalogued in different
catalogs long before Kepler was launched. They’ve dug up over a thousand old shots
of that chunk of the night sky where this star is visible and we can compare it brightness
in those to the stars nearby it. Those indicate that since 1890 the star has
faded by as much as 20%, though that has a lot of room for error. So again what’s left? Probably a lot of things. It might be one of these, it might be something
new. We’ll find out more between now and May
2017 when the event should occur again, and that will tell us a lot more too. We’ve been looking at it a lot with other
tools and again there is crowdsourcing to help get the funds for more tools. As this video comes out in August of 2016,
we’ve got about 9 months to go before we’ll get a lot more information and hopefully find
out WTF. One of the other developments was SETI looking
at it, and they didn’t find anything. I don’t think they expected to but they
had to try, no signals, but negative evidence is still useful to us. Now folks often suggest aliens might use entirely
encrypted signals, or not use radio at all or use lasers instead of omni-directional
signaling, we talked about that in the Fermi Paradox Compendium, but the encrypted idea
doesn’t work too well for the same reason I don’t need to break an encrypted code
to know someone is sending messages. Particularly since if this is an artificial
structure it’s as subtle and covert as an elephant blundering through a downtown metropolis. Encryption always has a cost so you wouldn’t
encrypt everything unless you had a reason to, and if that reason was trying to hide
your civilization building a giant structure around a star that noticeably eclipses it
isn’t the best way to doing that. It would be like a sniper or recon force sneaking
around the jungle in camouflage but stopping every few minutes to fire flares guns and
sing their national anthem through megaphones. Last Topic. If this were a megastructure what kind would
it be? Well it’s not a dyson sphere, if you’re
a veteran of this channel and the megastructures series you obviously already know that. Now a Dyson Sphere doesn’t need to be a
rigid shell around a star, it actually shouldn’t be and originally wasn’t meant to be when
Freeman Dyson came up with the idea, but we’ve talked about that before. It could be an early stage Dyson Swarm that’s
maybe 1% complete. But that ought to be symmetric. You might build a dyson swarm in stages but
you’d probably do it by making rings of swarm objects and adding to each ring then
adding a new ring. It’s easier to do it that way since those
swarm objects have virtually no escape velocity and so you’d need almost no thrust to move
from one place on the ring to a neighbor. Moving on the same ring of orbitals in a dyson
swarm could be accomplished with a space suit and fire extinguisher. Now that said, every dyson sphere begins somewhere
and if we were building one in our solar system it might start off as what I call a Planet
Cloud, something we discussed a bit more in the Ecumenpolis video a few weeks back. In that sort of case you’d expect the home
planet to basically develop a cloud of orbital habitats and solar collectors like a mini
dyson swarm itself, a big bubble, and to see rings stretching out from that initially. And that would look a lot like what we’re
seeing with Tabby’s Star So I don’t think this is what is going on
at Tabby’s Star but if it is a megastructure that’s what I’m putting my money on. Ditto you could mine a planet in a similar
fashion, you’d expect to see a big swarm of orbital and megastrucutres near a planet
you were strip mining and a lot of debris too, micrometeors aren’t as big a deal when
you don’t have to spend thousands of dollars a pound for your space stations because you
can armor them up and surround them with ice and rock, as we discussed in the Rotating
Habitats video. Considering the star appears to have dimmed
in the century we’ve been observing it too, you could have a fairly symmetric distribution
overall except where some planets are that are being stripped for additional construction
material. But here’s the big problem… there’s
no reason to do this around this star. We’re not seeing indicators of some sprawling
interstellar empire in this region, and again Kepler was staring at that patch of sky, a
lot of those stars were nearer or farther but it’s neighbors were all in that sample. It stretches credulity that any intelligent
life evolved around a star whose maximum lifetime is about 3 billion years, and again while
it’s probably pretty near the end of that, it might be younger too, which would make
that even more unlikely. So this isn’t someone’s home solar system,
and there’s no sprawling empire there with other stars exhibiting the same effects. This gets us into motives. Why would you pick a short-lived star, one
probably on the old side, as your one place to start setting up megastructures? You might mine inferior veins of ore or farm
not-so-fertile land but not until you’d already gone for the low hanging fruit and
there are tons of stars near that thing that are better candidates. Now maybe they just got there a century or
so ago, relatively speaking, its 1500 light years away so what we’re seeing now, in
terms of it dimming in the last century and our current observations, all took place when
the Roman Empire was falling. Maybe their home system is nearby and it’s
not cocked our direction and isn’t a full dyson swarm yet, maybe they just started grabbing
every system near them and we’re only picking up this one as one of the earliest and titled
at the right angle. But it does seem a stretch to think that this
is either A) Someone’s home solar system and they evolved very fast compared to us,
B) The sole place they’ve decided to do this,
or C) One of the first they did and the only one we can see so far. Mostly because even with C it’s incredibly
improbable a civilization could be setting up interstellar empires in full-blown Kardashev
2 style and be this close to us in space and also coincidentally this close to us in time,
just starting, while no others are further along a bit further away. After all if one civilization developed 1500
light years from us, then if we drew a bubble of space 3000 light years out, with double
the radius and therefore 8 times the volume and 8 times the stars, you’d expect 8 more
planets to have birthed technological civilization on average. And 1500 years in nothing on galactic timelines
so it would be really strange for one of those eight not to have a much longer headstart,
especially since this solar system, if it was their home system, would imply 3 billions
years is enough to become technological compared to our own 4.6 billion years. We talked about this general concept more
in the Dyson Dilemma, and the Fermi Paradox Compendium, so you might want to watch those
to get a better idea of how ridiculously this would stretch the odds on plausibility if
that’s not settling home just yet. It would be like getting struck by lightning
and winning the lottery on the same afternoon. So in summary, I don’t see much odds for
this being a megastructure, not just because it could be and probably is a natural phenomena
but because it just doesn’t fit the bill. Okay, that will finish us up for the day. Some quick channel notes:
The website should be up in a bit over week and we’ll talk about that more next time,
but what we have this week is the launch of the Soundcloud version of the channel, that
came out earlier this week and I’ve been uploading more content throughout the week. It will still be a bit before it’s all up
there, but all the playlist will be up as albums when this video comes out. Except for megastructures which was my test,
those each include an introductory segment to each playlist with some new material exclusively
available in audio. Soundcloud is free to listen to, and I have
enabled the download function so you don’t need to be online to listen to them. In any event that’s up now, and there is
some new content just for that format and I might do some more that way since audio
only is a lot easier to do than videos, and I never run out of topics. Speaking of that, next week’s topic will
take us back to the Existential Crisis Series for a look at Consciousness and Identity,
and we’re going to examine some of the concepts like cloning, including duplication of the
mind, hive minds, and distributed consciousness. Lots of familiar concepts from science fiction
in there and a lot very strange ones, along with some disturbing implications. Last note, the plan is still in place to do
about one video a month selected by an audience member picked by raffle from the channels
patrons. The intent is to do that via Patreon, but
I’m having the darnedest time thinking of a quick, fair, and easy method. I’ve noticed there are some online raffle
sites that let you do something along those lines but I haven’t really had the time
to investigate, and I feel like I’ve put that on hold too long. So if any of you have any ideas what would
be best head down to the comments section and I’ll open a thread to brainstorm about
it. Youtube doesn’t have a ‘pinned post’
option so if you’re having trouble finding it re-sort by ‘top comments’ and hit the
like button on that thread too to keep it at the top. Don’t forget to like this video too if you
enjoyed it, and share it with others. Until next week, thanks for watching, and
have a great day!
