
The ‘Dyson Sphere’ mystery deepens: Star keeps dimming - tonybeltramelli
http://www.wired.co.uk/article/dyson-megastructure-mystery-deepens
======
jasoncrawford
Here's a better explanation in a long (but readable) series of posts from an
actual astronomer, Jason Wright:
[http://sites.psu.edu/astrowright/2016/08/30/what-could-be-
go...](http://sites.psu.edu/astrowright/2016/08/30/what-could-be-going-on-
with-boyajians-star-part-i/)

In this series he details several hypotheses and ranks them.

~~~
daveguy
This is a series of posts with the summary and index here:

[http://sites.psu.edu/astrowright/2016/09/03/what-could-be-
go...](http://sites.psu.edu/astrowright/2016/09/03/what-could-be-going-on-
with-boyajians-star-part-x-wrapup-and-gaias-promise/)

Initial guide here:

[http://sites.psu.edu/astrowright/tabbys-star-
posts/](http://sites.psu.edu/astrowright/tabbys-star-posts/)

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dave_sullivan
Blackhole starlifting makes more sense to me than Dyson spheres (see section
on star lifting):
[https://arxiv.org/abs/1104.4362](https://arxiv.org/abs/1104.4362)

> Importantly, researchers have concluded that a thin accretion disk around a
> rotating black hole is the most efficient power source in the universe , a
> process up to ~50 times more efficient than nuclear fusion occurring in
> stars (e.g. Thorne 1974; Narayan and Quataert 2005). If any civilization is
> to climb the Kardashev scale, it would certainly at some point want to
> master that energetic source. We call such an endeavor black hole star
> lifting

Instead of a Dyson sphere, you're using a black hole (and apparent mastery of
gravity) to leech energy directly from the sun.

~~~
fuzzythinker
One can't get to the most efficient energy source without bootstrapping. And
dyson swarms may be one of the easier ways to get there. I like this video [1]
that explains this pretty well, from dyson swarms to kugelblitz. I do not
understand enough from the paper to know the difference between kugelblitz and
black hole star lifting though.

[1]
[https://www.youtube.com/watch?v=jW55cViXu6s](https://www.youtube.com/watch?v=jW55cViXu6s)

~~~
etatoby
PBS Space Time FTW! I'm waiting for their take on this star.

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delecti
As a really crazy thought, is it be possible that networks of Dyson Spheres
throughout the universe would explain the lower level of visible matter vs the
gravity we observe? That is, Dyson Spheres obfuscating their contained stars
as an explanation for dark matter?

Similarly, the heat would still escape from them. Could that explain the CMB?

(I expect that I'm way off the mark, but if nothing else it could make for an
interesting premise for some sci-fi.)

~~~
dandelany
> Dyson Spheres obfuscating their contained stars as an explanation for dark
> matter

No - MACHOs have been pretty well ruled out by now. "Several groups have
searched for MACHOs by searching for the microlensing amplification of light.
These groups have ruled out dark matter being explained by MACHOs with mass in
the range 1×10−8 solar masses (0.3 lunar masses) to 100 solar masses"
([https://en.wikipedia.org/wiki/Massive_compact_halo_object](https://en.wikipedia.org/wiki/Massive_compact_halo_object))

> Similarly, the heat would still escape from them. Could that explain the
> CMB?

The CMB comes from _everywhere_ at once, uniformly, all the dark spaces in
between stars is glowing. Dyson spheres radiating heat would just look like a
bunch of dots glowing in the infrared. I don't see how any number of Dyson
spheres radiating heat could produce a continuous, uniform field.

~~~
delecti
Ya know, gravitational lensing and the relative uniformity of the CMB are such
succinct and (in retrospect) obvious debunking of those ideas that I almost
feel embarrassed to have suggested them. :P

Thanks for the awesome response.

~~~
dandelany
Don't feel bad, there is a name for "MACHOs" because so many scientists have
had similar hypotheses about dark massive objects :)

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_andromeda_
If "By far most of the solar system's mass is in the Sun itself: somewhere
between 99.8 and 99.9 percent", then I can't help but wonder if there is
enough matter to cover the sun's surface area to create a real Dyson sphere.
Where would this matter come from? Is there enough matter in left in the 0.1%
(shared by the rest of the solar system) to completely engulf the sun?

~~~
fogleman
I was curious about your idea, so I whipped up some numbers in Python. A
1-meter thick spherical shell at 1 AU from our sun would be 0.02% of the
volume of the Sun, or 260x the volume of the Earth. If you go down to 1-mm
thick, you only need 0.26 Earths. :)

~~~
mrfusion
You could be a lot closer too. No reason to do one au.

~~~
david-given
Heat, actually.

All the energy the star produces has to escape into space somehow. The way it
does this is by heating up the sphere until it radiates out into space at the
same rate at which the star irradiates the sphere. The bigger the sphere, the
cooler it is, because it has more surface area to radiate away heat.

So if your sphere is too small, it may end up glowing at red heat, which might
make it difficult to live on.

Calculating the temperature is straightforward:

[http://www.aleph.se/Nada/dysonFAQ.html](http://www.aleph.se/Nada/dysonFAQ.html)

~~~
jxy
You can't assume that they can build a Dyson sphere while their technology is
as limited as us earthlings.

If you can imagine some alien species building a mega structure in such a
short time, you should be able to imagine that they have a way to transfer and
store that amount of energy.

The laws of thermodynamics, as we know it, prevents 100% efficiency in doing
that, but if they have a directional heat dissipation device, and their
generator is highly efficient, we will hardly have any chance to detect that.

I can imagine they could have some version of our power plant, only orders of
magnitude more advanced. Instead of moving electrons, they could be generating
and moving matter anti-matter stuffs.

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test6554
Occam's razor: If you see mysterious dimming in a star, it's definitely
aliens.

~~~
s_kilk
The implication seems to be that construction is ongoing, and the pieces of
the sphere are being moved into place.

~~~
haneefmubarak
Or rather, since all stars are multiple light-years away from us, construction
_was_ ongoing.

~~~
drjesusphd
A suitable definition of "now" is our past and future light cones.

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neals
So interestingly, hiding you star in a Dyson sphere, turns it into the loudest
beacon in the galaxy, for a while.

If we wanted to be 'found' by aliens, we should do this to our sun.

~~~
jerry40
Also we can use this as a trap. Just choose a star, make it darker and wait.

~~~
drzaiusapelord
A trap for what exactly? By the time your society can do this to a star,
you're not exactly fighting others for resources. You're very much into post-
scarcity territory and the traditional motivations for conflict are long gone.
I never understood the scarcity mentality we apply to hypothetical super-
advanced civilizations. This is like expecting Jesus to take your wallet or
the Buddha to kick you down the stairs.

If there are other advanced societies out there I seriously doubt war is their
main motivator in space exploration, the same way Voyager and Curiosity are
unarmed. Sure, that makes for fun sci-fi stories, but real life is governed by
fairly simplistic game theory rules, at least from a high-level perspective.
The motivators we have been given through evolution will be the motivators
they have as well. Unless we're dismissing evolution as only a local
phenomenon, we should expect similar beings to ourselves. I think the 'hostile
alien' scenario shouldn't be our default. Sadly, that approach sells ad
impressions and schlocky futurist books and influences a lot of people to
believe things that are pretty questionable.

If we discovered a primitive species in the European seas we'd be tripping
over ourselves to preserve them and study them and to make sure they never,
ever get hurt by us (or a stray asteroid or anything we could prevent). We
wouldn't be conquering them with robot subs for their pretty coral jewellery
or sub-surface oil or whatever. We have enough pretty things and energy here
on Earth and in unihabited places if need be. Life is rare enough that we
don't need to attack other life for resources, assuming we ever find any.

~~~
joeclark77
You might enjoy reading John C. Wright's "Count to a Trillion" series, which
does some thinking about how starfaring alien races, governed by game theory,
might actually operate.

I don't think there's ever going to be a point when a race has "enough" and
doesn't want to explore or build any more. Our ambition should grow with our
capabilities. Once you can control a star, why not work on a galaxy?

~~~
maxerickson
The big reason is that you'd need a brand new physics to project power over
interstellar distances.

Every outpost of the empire will essentially have unlimited manufacturing
capability and it will take decades to project force, decades the outpost can
spend making sure the amount of matter they have devoted to war exceeds the
tiny amount of war matter the central empire threw out into space.

~~~
joeclark77
The series of novels specifically deals with time frames much longer than
"decades". The first book spans a few centuries, the second and third span
millenia, the fourth spans tens of millennia, and the fifth and sixth (not out
yet) are supposed to reach much farther.

The big idea of the book is that Einstein isn't wrong about C being the speed
limit. Therefore, to be a starfaring race requires the ability to make
commitments and hold to them over extremely long timespans. The connection to
game theory is that, as in the Prisoner's Dilemma, the only way you can really
make predictably right decisions in cooperation with other entities is if your
decision-making formulas are spelled out mathematically in advance; so all can
predict how you will act. The first book begins with mankind discovering the
galaxy's "rules" on a kind of signpost at a nearby star.

Read the books!

~~~
maxerickson
Maybe I will, I'm kind of burnt out on scifi.

My point is that the very concept of an interstellar resource war, and thus
the concept of interstellar control, is incoherent given our present physics.
You can take over a system that isn't technologically enabled, but that's it,
the resources available to a technologically enabled system are greater than
the resources that can be sent into the system.

~~~
joeclark77
I'm not sure that's really true. What would it take to wipe out all the
denizens of a star system? Maybe a few million atomic bombs? Certainly less
than the mass of a small moon. And if that then gave you control of a whole
star system's worth of matter and energy, it should be more than enough to
fuel the conquest of the next star, and so on.

So it's certainly feasible for an advanced race to build a star empire; the
question is why they'd want to do it. If we're talking about humans you might
say ambition or imagination. If Vulcans, maybe they'd think it logical to pre-
emptively become stronger than any potential aggressors.

~~~
maxerickson
That would work against a system incapable of similar production, but given
roughly equal capacity, the target system could devote a small planets worth
of material to defensive missiles.

You could slam a bunch of mass into a system at extreme speeds, but then they
just have to hop into life boats until the storm ends (if they have the
capacity to ponder traveling the stars, they have the capacity to spend a
decade on a space station).

------
littlegreenb18
It's Morning Light Mountain

~~~
markild
He.. She.. It.. They? Didn't create the sphere though!

To anyone not getting the reference, read Pandora's Star by Peter Hamilton[1].
It's a lovely read.

[1]:
[https://en.wikipedia.org/wiki/Commonwealth_Saga](https://en.wikipedia.org/wiki/Commonwealth_Saga)

~~~
soylentcola
Good timing because I just started this last week after finishing Vinge's
"Zones of Thought" series. I guess I'm on something of a space opera kick
lately.

~~~
daveguy
Are the sequels/prequels worth reading? I read the first one last year and
enjoyed it, but the follow up reviews made it seem like the others novels
might spoil it.

~~~
mikeash
The first two are great. Deepness is the best one, IMO. As for anything beyond
that, I'll just say it's so sad he stopped at two.

------
brador
If I was building a Dyson sphere I would launch multiple modular solar panels
into orbit around the star. This is the cheapest scalable way to do it while I
collect resources and send more as my energy needs increase.

The problem then is getting that energy out. I'd use lasers from my panels to
my planet. That means my solar panel collective in orbit around the star will
have to always point to my planet for maximum efficiency so I don't have
useless panels since there's no way i'm building a battery at star energy
scale on each panel.

The dimming you see would then be based on the orbit time of my planet around
the star, since the panel half halo will always be pointing at my planet.
Essentially geostationary around the star.

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mckoss
Why not just a binary dwarf sucking material (somewhat chaotically) out of its
more luminous twin?

~~~
simcop2387
We'd see bits of time where the dwarf was in front of the twin and burning
much much brighter, the accretion disk on the dwarf would be larger than the
dwarf and giving off high energy photons as it consumes the incoming matter.
We haven't seen any spikes in the light level, only dips. It's possible it's
behind the other star still but I don't think we've seen anything else to
indicate that.

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lordnacho
So if you make a Dyson sphere, your planet is either inside or outside of it.

If it's outside, you might get complaints about the shutting off of the
day/night cycle.

If it's inside, you get all the sun's light reflected off the inside of the
sphere. Kinda blinding.

~~~
gpderetta
your planet (and most of the solar system) has been dismantled to build the
Dyson sphere, the system is now ruled by DAO-like AI agents running on
computronium. You upload yourself and a few other survivors on a small can-
sized spaceship and flee the system in search of a new home.

~~~
humbledrone
/endsynopsis "Accelerando", Charlie Stross (2005)

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trelliscoded
For anyone who has some spare time, here's an enormous time sink:

[http://www.orionsarm.com](http://www.orionsarm.com)

Don't click on that if you have stuff to do today.

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s_kilk
My wager: It's a fleet of mega-spaceships passing across the star, probably
much closer to us than to the remote star. Hence irregular dimming that
doesn't seem to repeat predictably.

~~~
jerry40
Keeping in mind that the star is 1480 light-years avay, the fleet passed
across the star about thousand years ago. Or they're still flying toward us...

~~~
joeclark77
They don't have to be right there by the star. They could be small ships just
a few million miles away, maybe.

~~~
GFK_of_xmaspast
Space is, technically speaking, "really big".

~~~
jawilson2
You just won't believe how vastly, hugely, mind-bogglingly big it is.

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mmmBacon
Measuring absolute brightness is hard. It would be good to compare the
measurement error is in brightness of a reference star of about the same
magnitude and distance(and even perhaps a known variable star) to the observed
changes in this star.

In the lab under ideal conditions with ideal light sources, it's pretty common
for there to be >2.5% error in these types of measurements. For those used to
dB unit, this is a ~0.1dB change. In optics, it's very easy to introduce error
at this level.

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jlebrech
so there are in the middle of building the dyson sphere?

~~~
jameskilton
My issue with the whole "alien civilization" idea is that we are seeing what
happened around that star some 1,400 years ago, which means if they were
building a Dyson sphere that long ago, it's unimaginable what tech they have
today. I have a hard time accepting that an intelligent species could be
_that_ far ahead of us technology wise, but I could be wrong!

~~~
Jtsummers
The universe is billions of years old. There's no reason to think that our
arrival (as an intelligent species) is uniquely tied to this particular time
period.

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chanandler_bong
I still say it is a giant alien Aldis lamp, and we just don't understand their
Morse code.

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krige
My wager: The star is being eaten by a cosmic horror called Hellstar and it
will be soon coming our way. Now excuse me while I take off my Junji Ito hat.

~~~
kabdib
Or a space goat. My money is equally split between a Dyson sphere that is
tearing itself apart (because: low bidder on the project, some things just
_never_ change) or a gigantic space goat that is eating the star.

Both are equally likely :-)

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trm42
Unicron, devourer of worlds!

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joeclark77
Maybe it's Slartibartfast's workshop.

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simonh
Starkiller Base powering up!

~~~
tonetheman
exactly what i was going to say!!!!!

