Hacker News new | past | comments | ask | show | jobs | submit login
Tabby's star is dimming at an incredible rate (sciencealert.com)
375 points by ChuckMcM on Aug 6, 2016 | hide | past | web | favorite | 171 comments

Good ol' PV on Kinja (from the linked gizmodo article: http://gizmodo.com/the-so-called-alien-megastructure-just-go...) has some interesting thoughts, as usual.

> The biggest axe against it being an alien megastructure project is the fact its an F-type star. F-types only live a couple billion years, depending on mass.

> But the drop in the radiant flux... a sustained drop. That could be something far more interesting. If you could do stellar engineering... you could draw the material off an F-type star while altering its core. You could reduce the mass to a G or K star, greatly increasing its lifespan... and gaining trillions upon trillions of tons of raw material with which to build an alien megastructure...

I'm sorry, I must've missed something important because I've seen pointers to this post elsewhere. Who exactly is "PV on Kinja?"

"PV" is a user's name on Kinja, which is the commenting system that gizmodo et al use.

I think it's a reference to the first comment on the article linked.

Spectral type isn't 1-1 correlate with the star estimated life. Depends on the star mass. Our Sun was one time a F type star.

Do we have a "longevity" estimate for Tabby's star?

By estimating how much starlifting would explain the observed luminosity drop, and then backing out the expected increase in the star's life against its flux decrease one could estimate how efficient the "aliens'" energy-harvesting technology is (coupled to a financial discount rate).

Plug its estimated mass (1.43 solar masses [1]) into the expression for main sequence lifetime [2] and you get ~4.1 billion years. But we don't know how old it is (the prevailing assumption seems to be it's old enough to have settled into staid middle-age behavior, making its variability harder to explain [3]).

[1] https://en.wikipedia.org/wiki/KIC_8462852

[2] http://astronomy.swin.edu.au/cosmos/M/Main+Sequence+Lifetime

[3] http://www.americaspace.com/?p=87801

Question for you Timex Eclair, can I use a star as the engine for my megaship? Pointing all the photons in direction?

Like this?


Of course if this was happening we'd see some unusual proper motion from KIC 8462852. Which we're not. (Did someone check?)

They're coming right for us!!! O_O

You now have to move the whole sun, so I don't see how the problem got any easier by escalating it to huge proportions? Unless you want to leave the sun behind, but then you will lose your propulsion after getting going.

You can you use a giant mirror, that directs light to your ship's sail.

I really wonder what would happen if you really had a giant mirror reflecting all the Sun's energy back to itself

It would increase the sun's temperature causing it to expand. I guess eventually it would expand out to reach your dyson mirror.

Of course there would be all sorts of secondary effects, lowering the density in the core could slow down the rate of fusion, increased temp would increase it, but no garuntee that the effects would cancel. Also depending on how far out your mirror is the core might not ever notice the change. The outer layers could heat up and destroy your mirror before the increased temperature reaches the core.

Isn't that basically what happens inside the Sun's core anyways?

Two reddit discussion that might be able to answer some questions we have here:



They also contain links to the resulting paper itself

Reddit user sigbjoernwilderness's idea is pretty wild... can it be easily ruled out?

> Is this the last remaining explanation after Montet/Simon?

> The dimming comes from the shadow of a spaceship traveling on an (almost) straight line from KIC8462852 to Earth. The slow continuous dimming results from the increase of the apparent size of the approaching ship while Earth/Kepler is in the penumbra. The irregular dips happen when Kepler accidentally passes the antumbra. A rough estimation by simple geometry would suggest that the alien spaceship is quite big (> 100 km diameter), significantly slower than light velocity (< 0.05 c) and has now almost reached its goal (< 2 ly away), arriving at Earth within the next 100 years after a journey of several 10,000 years. (cf. http://archimedes.soup.io/post/632873371/) The c200 days of "rapid decreased flux" between Kepler-day 1100 and 1300 (first half of 2012) which Monet/Simon reported, followed by a series of large dips after day 1500, would suggest a course correction with the space ship now on its final homing trajectory. -- Comments?

-- https://www.reddit.com/r/KIC8462852/comments/4w7qfi/ben_mont...

    can it be easily ruled out?
Yes: parallax breaks it. If something's colinear with a star today (and occults it), it won't be colinear 6 months later, when the Earth's on the other side of the sun.

At 2 light years for instance, that spacecraft would trace an apparent ellipse 3.3" in diameter, while Tabby's star (1,480 ly) would be stationary (0.004" parallax). In comparison, the star's apparent disk is just 30 μas wide (0.00003").

If I'm doing that math right, it works out that to not be ruled out by parallax, the object would have to be almost 2 AU in diameter if it was within a few light years of Earth. That seems pretty ridiculous--now we have them not only building a megastructure, but flying it to Earth!

However, I wonder if there is a way to save the idea without requiring a ridiculously large spacecraft? Suppose instead of one ginormous ship, it is a fleet of big ships each big enough to cause irregular dimming if that ship happens to get between Earth and KIC8462852. If the fleet is spread out, it could then be that one ship or another ends up between Earth and KIC8462852 at several times during one Earth orbit around the Sun.

That would give us the irregular dimming throughout the year.

For the slow continuous dimming, perhaps that is something going on with the star itself. That could be what made the inhabitants of the system decide to build a fleet of big ships and leave their weirdly behaving and very scary star.

Maybe the visible size of the ship is bigger, as it's unfolding / building a solar sail to brake using our sun's radiation? (like a parachute on a drag racer). Ah, but 2au is probably still way too big?

What if the parachute was a big magnetically contained gas cloud ?

Excellent point... that answers my question. Thanks!

There's a comment [1] in the other reddit thread that somewhat rules this out.

> That doesn't even make sense when you're flying within the Solar System. Stuff moves, so you have to fly towards where it's going to be, not where it is.

> The star is far enough away to be treated as a point source, with its light forming an apparent cone with the Earth's diameter. It doesn't intuitively make sense, at least to me, that the ship would stay within that cone as it corrects for the motion of our Solar System (and its own) within our galaxy. Remember that this dimming effect has been observable for several decades.

Then again, aliens don't have any obligation to make sense to us.

[1] : https://www.reddit.com/r/Astronomy/comments/4waozn/new_paper...

You just need a big enough ship.

A while back I had a plan for a science fiction setting: an intergalactic ship is approach Earth. The people who sent it thought big, and as a result the ship has at its core an enclosed star (a miniature Dyson Sphere) as a gravitational anchor and power source, and round it is orbiting a vast swarm of asteroids and habitats with a few million times the living space of Earth, inside which civilisations endlessly rise and fall.

The plot centred around this thing going to make a class pass by Sol in a few years at 0.01c, with the gravitational effects pretty much dooming the Earth; so the current lead civilisation sends some ships on ahead to evacuate the Earth. (Big ships. I did the maths.)

The story never gelled, but I think it's plausible that my ship would produce these effects.

BTW, if this turns out to be true, I want credit.

You might enjoy some of Liu Cixin's stories, which are often similar to that: https://www.amazon.com/Wandering-Earth-Classic-Science-Colle...

Yet another book recommendation:

Terre en fuite (Fleeing Earth) (1960) by François Bordes (pen name Francis Carsac), though, there is still no translation in english of that gem, where Earth and Venus was converted to spaceships for running away from exploding Sun!

Yet another book recommendation: Marrow by Robert Reed. Some similarities to your story :)

Wouldn't the ship collapse under it's own gravity?

Or maybe we are the ones traveling to the star.

Keep it up! I'd read that.

> if this turns out to be true, I want credit

You cool if we blame you too? :)

Maybe they are taking the long about route on purpose to let us know about their arrival!

Unless military tactics dictate that they try to "hide" in the cone since they first picked up our radio signals... Even If they're on a "civilian" mission, they might have navigators/a captain with military training...

Not plausible because:

a) Tabby's Star is roughly 1500 light years away from us; we only began emitting radio signals ~150 years ago (at most -- assuming propagation from early telegraph wires; not actually very likely) and it'd take ~3000 years for our signals to reach the vicinity of Tabby's Star and indications of a reaction getting back to us,

b) "Military" is a category error on this scale; the energy budget required to generate the sort of luminosity changes we're seeing around Tabby's Star by deliberately occulting it are mind-blowing compared to anything we've ever achieved. Might as well speculate about an ant-hill (us) wondering about the military intentions of an M1 Abrams tank driving across the Iraqi desert (hypothetical alien actors at Tabby's star) -- either they aren't going to drive over us, or we just encountered an Outside Context Problem.

A) but if the ship is only 2 ly away, they could've changed maneuvering a hundred years ago.

B) sure.

It could be a way to announce their arrival passively.

That would assume they know we're scanning the skies for short-lived and easy-to-miss flux variations.

The corollary: if there are aliens around KIC 8462852 they don't care that what they're doing is visible for 1500 light years around them.

Do spaceships travel in a straight line? I thought their trajectories are heavily curved in really weird ways due to the garvities of stars and planets around them. Please enlighten me!

It depends on the frame of reference, which can be somewhat arbitrary.

A ship can sail a straight line from Falmouth to Boston, but that motion can be described as an arc because of the curvature of the Earth. Add in the motion of Earth's orbit, and the shape of that motion changes again. Add in the Solar System's motion relative to the Galactic Centre, and it's yet another shape.

It's all a matter of perspective :-)

The straight line from Falmouth to Boston is only straight on a 2d map, because of particular transformation from 3d surface to 2d plane. Nothing to do with reference frame.

You indeed can change a curve into a straight line by manipulating the frame of reference, but it would need to be very contrived - basically you follow the object movement and add constant translation and some linear movement on top of that (one example - camera is in on a kite tied to the ship, and the rope is progressively loosened).

I think you overestimate the density of stars in the universe. If I remember correctly there are typically a few lightyears between each star (on average).

There would still be a curved orbit around the center of the galaxy. That is a bit like arguing that a mission from Earth to Mars would travel in a straight line because there isn't anything in between them.

How can a ship 100 km in diameter cause any significant dimming of a star, which is 21,980,000 km in diameter? It would have to be pretty close to here and lined up just so perfectly.

Why even assume it's a spaceship and not an asteroid or a rogue planet?

The moon is smaller than the sun, and yet still we have eclipses. It's just a matter of perspective.

The object[s] would have to be lined up. That's why an artificial object intentionally traveling to Earth is in some sense more plausible than an asteroid, which could be headed in any direction.

Why would it be only one object? It could be a belt of random sizes and shaped asteroids that is between us and the star?

Or the entire Vogon fleet?

"Ok, one last time... these are small, but the one's out there are far away" - Fr. Ted Crilly


> Why even assume it's a spaceship and not an asteroid or a rogue planet?

Specifity bias. It "feels" more probable to have object going here because someone send it here, than to just have object going here.

Because we're brainstorming here! They're not assuming anything.

But yes, that's exactly the theory, that the starship is somewhere between us and them, and it sometimes dips into the focal point of light.

Tabby's Star has a twitter account also. It's unclear why no one is asking it direct questions about its intentions: https://twitter.com/KIC8462852

Sunspots, debris and/or a distant cloud are not completely ruled out: https://arxiv.org/abs/1608.01316


The leading hypothesis, based on a lack of observed infrared light, is that of a swarm of cold, dusty comet fragments in a highly eccentric orbit.[12][13][14] Many small masses in "tight formation" orbiting the star have also been proposed.[9] The changes in brightness could be signs of activity associated with intelligent extraterrestrial life building a Dyson swarm.[9][15][16][17] The SETI Institute's initial radio reconnaissance of KIC 8462852, however, found no evidence of technology-related radio signals from the star.


Safe to say that a civilization that can build a Dyson structure isn't using any 20th-century coherent modulation types that SETI could detect.

SETI is only useful for catching civilizations in the ~100 Earth year-equivalent span between their development of wireless tech and information theory. There's nothing to listen to but white noise after that.

SETI have some dubious criteria like that an alien civilization would emit at Hydrogen resonance frequency because is a universal constant. Any HAM radio operator or telecommunication engineer know well how bad is trying to emit anything on Hydrogen band because is full of natural noise.

I understand the hydrogen line to be used tho because the noise is constant and any deviation or pattern could be easily identifiable

The problem with noise is that your signal has to be bigger than the noise in order to be intelligible. Preferably you'd find a channel with less noise, not more.

Your signal doesn't have to be bigger than the noise. But your effective channel bandwidth is limited by the signal/noise ratio:


Shannon’s channel capacity criteria for noisy channels Given a communication channel with bandwidth of B Hz. and a signal-to-noise ratio of S/N, where S is the signal power and N is the noise power, Shannon’s formulae for the maximum channel capacity C of such a channel is

C = B log (1 + S/N)

(log is to base 2)

For example, for a channel with bandwidth of 3 KHz and with a S/N value of 1000, like that of a typical telephone line, the maximum channel capacity is

    C = 3000 * log (1 + 1000)  = 30000 bps (approx.)


On SETI's use of the Hydrogen line:


The hydrogen line (1420.40575 MHz) is the precession frequency of neutral hydrogen atoms, the most abundant substance in space. It happens to fall in the quietest part of the radio spectrum, what's known as the Microwave Window. Although there may not seem to be a lot of loose hydrogen atoms about (there's perhaps one per cubic centimeter of interstellar space), the interstellar medium contains a lot of cubic centimeters. So these individual atoms chirping away at 1420 MHz make a powerful chorus, which is readily detected by even small radio telescopes.



At 1420 MHz, even with an S/N of 1/1000, you'd have about 2,048 kbaud channel, if I'm doing my maths right. Given that an intentional signal could be highly directional, this seems possible.

This is speculation. There are all kinds of examples we have of "ancient" technology that are still in everyday use today - knives, for example.

There's no reason to think that something else would abandon using EM as a transfer of communication.

That's not what I said. Tune a general-coverage receiver to the frequency of an HDTV station, and what you hear is what the SETI folks will hear, whether there's a signal there or not.

Also, from what I understand, the last several decades of our radio history were spent optimizing everything so that signals keep as much to the ground as possible - emitting TV into space is wasting money.

Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground. And even the terrestrial radio and TV stations still broadcasting are strictly power-limited to reduce geographic overlap.

Most long-distance communication travels over wires too--everyone uses fiber backhaul. Phones and computers use EM (cellular, WiFi, Bluetooth) but the range is very short, so the signal power is far too low to report us to the universe.

On top of that, most entertainment and communications signals today are digital, and many are encrypted. It's going to sound like noise to a receiver that doesn't know the encoding and/or have the encryption key.

The most powerful space-facing EM emissions we make today, as a species, is probably RADAR, not a form of communications.

> Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground.

Since I don't think its coming from manned satellites where the content is generated, I'm pretty sure there is a space-facing signal involved in satellite TV as well as a ground-facing signal.

My understanding is that the uplink signal's power is much lower than the broadcast power, because each uplink signal is focused on its satellite by a parabolic dish.

Sure some of the uplink will make it past the satellite, but that's a fairly low-power beam that would need to intersect an alien antenna to be heard.

>What they saw was that, not only did the star's light output occasionally dip by 20 percent - the weird behaviour scientists first spotted last year - but over the course of the observations, its entire stellar flux actually dimmed.

It would be interesting if this turned out to be like the OnOff star from A Deepness in the Sky.

I really like mysteries like this one. They defy simple explanations and force us to work harder to learn more about our world. Sort of like the bright spots on Ceres, which are still pretty awesome.

Reminds me of when quasars were first discovered and people thought they were part of some alien telegraph system.

I find it funny that a clickbaity title like that bothers to tell people to "not get too excited" about the possibility of anything involving aliens. Further, you know what? I say this is something to be really fired up about. We've got a phenomenon here that matches nothing we can come up with theoretically. Live it up!

It's not like this is right on our doorstep but I'd still be more comfortable if this was happening more than 1480 light years away.

Well whatever it is, we probably have 1000+ years to save ourselves right? If whatever caused it comes at us at 50% light speed, which sounds unlikely given how fast that already is, we'd still have 700 years.

I'm pretty sure that if human's resources were suddenly all turned towards getting the hell out of here, we could certainly pull it off for a good part of the population in a few hundred years. Whether we'd eventually survive, after decades or centuries in space (before we manage to find and arrive at a new planet, if any), is something I'm less certain about, but I'd still estimate the odds to be fairly okay, especially with 1000+ years to prepare.

"Well whatever it is, we probably have 1000+ years to save ourselves right?"

No. That time has already passed. If we see signs that the star will go nova "in one year", we have one year, not 1481.

The popular idea that we see "the past" in the sky is not really the best way to think about it. It is far more accurate to say that there is no such thing as "the" present, and what we see in the sky really is our present. The view that we're seeing "the past" is ironically perhaps less sophisticated than the more naive idea that it is simply our present we are seeing in the sky. (And at the moment, there aren't any other "presents" that we much care about.)

The thing that really saves us is that even supernovas that far away can't really hurt us because of the inverse square law. A quick Google search shows one site estimating that a supernova would have to be 50 ly or closer or so: http://www.howitworksdaily.com/could-a-supernova-destroy-ear... Something would have to be beamed specifically at us, and the only natural phenomena I know that can do that are black holes and pulsars, neither of which seem to be what is at that star, and probably still wouldn't be powerful enough to hurt us at that distance.

From an intelligent life angle, what would really save us is that, aside from a number of planets to observe, we haven't really been all that interesting until the last 100-200 years; when we started actually emitting signs of intelligent life in to space.

Ah, but this is only true about we, humans rather than earth/solar system. It cannot be excluded that other sources of radio have been around here in the past :)

It also assumes that outside observers have the same difficulty understanding the make-up and probable evolution of a system as we do. If they were able to observe that Earth would have some properties they were interested in, or would be a likely candidate for such, then they wouldn't need us to announce our presence to guess it.

IMHO the aliens will not be specifically seeking life that is intelligent. Singularities and interstellar traveling alien civilizations share a problem. If one is in essence immortal the only purpose that can endure forever is the pursuit of new knowledge. Even if alien entities are able to learn all there is to know about all the other sciences, biology will be inexhaustible as the novel patterns that can be produced by evolution are effectively infinite. The biosphere of just our planet where the latest estimates are that there are a trillion species if you count all the microorganisms, probably contains more information than all the lifeless planets and stars in the galaxy combined. The aliens will value biodiversity more than we do. And if they arrive they will oppress us "only" to the extent required to counteract our propensity to cause species extinctions (including our suicidal alteration of the planet's climate). I actually would prefer that the Singularity or the aliens arrive sooner rather than later as I have less and less hope of our species getting its act together on its own.

>> biology will be inexhaustible as the novel patterns that can be produced by evolution are effectively infinite

But why do you assume they would be interested in observing the patterns that actually have been produced, instead of running high-precision evolutionary emulators that can generate patterns that could be produced at a much higher rate, and maybe even some automated filters to condense it down to "interesting" stuff? It's still knowledge, and there's no innate value scale for knowledge which says that things that have "actually happened" are more valuable.

In fact, how's that for Fermi paradox? Civilizations that are sufficiently technologically advanced to communicate, much less travel, across the stars, are also sufficiently technologically advanced to simulate the things they are interested about and get answers faster that way.

Basically, the end result of any civilization is creating, maintaining and expanding a simulation of the universe. Which, of course, goes recursive...

Thermodynamics still limits what you can compute and, given the output of a single star, you're still limited in what can be computed.

But I think it's a mistake to try to characterize any civilization by a single motivation. People on Earth do things for many different reasons and I think we should expect the same of alien civilizations even if single motivations tax our imaginations less. The questions is if any of the motivations driving a stellar civilization would be enough to prompt the establishment of colonies. I don't think you can say that the answer will be 'no' reliably for every civilization that might arise and it only takes on to colonize a galaxy in short order (by cosmic standards). Hence sophisticated life is probably very rare.

In a similar vein, a possible Fermi paradox solution would be that civilizations sufficiently technologically advanced to travel between stars are also advanced enough to develop good VR and learn which buttons of their brains to push, so they all end up stuck in virtual worlds, or even wireheaded.

A counterargument to that would go along the the similar lines as to why we don't, and can't, resolve wars by e.g. playing chess (or StarCraft). Even if all nations mutually agreed that the shall will be won bloodlessly by some other kind of competition, the first nation to nuke its enemies would be a winner. In conflict situations, you want to seek as much advantage from the "most real" reality as you can get. So, in your recursion example, you'd travel up the call stack...

You can't just wave a wand called "emulation" to hypothesize whatever speed, precision, or rate of calculation you want. Emulators are physical objects and you'd need to show that it's possible to build an emulator that calculates the same amount of information as the Earth's biosphere, but faster, more precise, etc.

Then, once you have the attributes of that emulator, you'd have to calculate how long it would take that emulator to deliver the same information that can be harvested today on Earth with simple observations. And even if it completed, how would you confirm it is indeed the same information without traveling here to check?

The energy budget would be immense of course, but heat management might be the limiting issue on how fast it can run. It's hard to dump heat into space.

I'm not intending to argue one or another about hypothetical god-like alien civilizations. It's just a pet peeve when programmers make open-ended claims about simulations or emulations without considering physical constraints. We tend to think of electronic computers as powerful, but their information handling capabilities are quite slow and diffuse compared to what biology has produced on Earth so far.

Thinking that pursuit of knowledge is only activity for immortal is naively idealistic.

Elimination of of all life not like me. Or simply eliminate life that might singularity and become a threat. Even if, who's to say one aliens pursuit of knowledge latest experiment dose not require and earth sized amount of raw materials.

Our aggression reflects the zero sum physical resource context of our evolutionary past. Knowledge in contrast grows fastest through cooperation. As power including the power to defend oneself grows with knowledge, knowledge seeking entities will quickly evolve to maximize cooperation. And as many have pointed out, unlike most of our sci fi, it is very unlikely for two alien civilizations to meet where their technology levels are similar - one will be permanently vastly advantaged over the other. Aggression will be pointless - the pecking order will be obvious. As to your last point I am sure lifeless planets will do for any experiments.

> If one is in essence immortal the only purpose that can endure forever is the pursuit of new knowledge.

That's making a lot of assumptions about alien psychology, believing they're going to have the same goals as us. Why not

1. Propagation of your species, forever

2. Expansion of your territory until the entire Universe is yours

3. Endless pursuit of pleasure

4. Propagating religious beliefs, or something we'd recognize as such.

5. Escaping this Universe, which will eventually end.

My unprovable assumption is that only beings who value knowledge and cooperation highly enough will get to the point of crossing the difficult technological threshold of achieving singularity or space travel. I think the more likely Achilles heel for my scenario is sexual selection - the trap that perpetuates selfish behavior in both sexes even when there is no resource scarcity. Even in this, humans at least are sometimes able to escape the trap by being meta enough to see kindness as strength and beauty. I think the fastest, and most likely first, route to our singularity will start with reverse engineering one human mind, and I will hold onto hope that that mind will hear the call of light, and the truth and beauty feedback loop will be unstoppable. It helps that I also believe that as information increases, morality converges on a process for maximizing the long term preservation of information (where on this planet, human minds are the most information dense and therefore the most valuable things we can preserve). /end sci fi sermon

An anthill-like species can value cooperation among themselves without necessarily valuing knowledge for knowledge's sake - imagine the Hive Queens from Ender's Game, or MorningLightMountain.

Hmm, that's actually not true. For example a spectroscopical analysis of the composition of be earth's atmosphere would reveal very unusual properties which would be a sure telling sign of photosynthesis, and that has been occurring for billions of years.

Yeah, it looks like a supernova 1500 ly away might produce enough gamma rays that we could actually measure their effect on the ozone layer but not enough that it would be concerning.


Unexplained dimmings do give rise to the question of "Is it about to explode" but we have a good sense of how often large explosions occur in galaxies because they're so obvious and so I suppose I shouldn't be concerned about natural phenomenon. And given the potential expansion rates of being who could create megastructures like this our priors on that explanation have to be pretty low.

> No. That time has already passed. If we see signs that the star will go nova "in one year", we have one year, not 1481.

He specifically referred to something traveling at half of the speed of light, in which case it would arrive in >=1480 years not one.

So what's the risk if it turns supernova in one year? As you say, it's 1500 ly away, not <50.

You sound way more expert on this than me (I had no idea lightyears had a notation, ly, nor that supernovas are dangerous to us as far as 50ly away), so I'll assume what you say is accurate, but I still see no imminent threat.

I'm also not suggesting we'd have the full 1481 years, since we don't see what's presently there but what was there, but as long as the phenomenon doesn't travel at the speed of light (and it doesn't, or we would be experiencing it already, since we can observe the effect) we still have time.

Finding information on this appears to be kinda hard, but it looks like the best estimate for the 'kill radius' of a supernova (i.e. will cause mass extinctions) is 30 light years. So this is about two orders of magnitudes away, which means the effect will be two orders of magnitude lesser.

Eta Corina is a double star containing at least one hypergiant that's going to go supernova any epoch now, so it gets studied a lot. It's 7500 light years away and I believe it's judged not to be a threat, although there may be ozone layer damage and it's probably not healthy to be an unshielded astronaut.

However supernovae appear to emit gamma ray bursts along their axes. These can travel very large distances. Eta Corina's isn't point our way, but Tabby's Star? Who knows. 1500 light years is basically point blank range for a GRB, so if one is coming our way that would be very bad news. Like, worse than mass extinction grade bad news.

"So this is about two orders of magnitudes away, which means the effect will be two orders of magnitude lesser."

Inverse square applies here; moving 100 times farther away makes the effect 10,000 times less.

(I have to say it "applies here" because people sometimes overapply the law. It only applies when something is spreading out in an even sphere. However, that applies to supernovae, or at least close enough.)

You're right that I neglected gamma ray bursts. But it also doesn't seem like this star could be building up to that, since it requires conditions not evident there. (I'm just following up on my point, not implying that you claimed otherwise.)

> Inverse square applies here; moving 100 times farther away makes the effect 10,000 times less.

Oh, bah. Yes, of course. My upbringing in Flatland is obviously showing.

Excellent riposte, good sir!

I believe the most powerful gamma ray bursts, the ones that are powerful enough to strip away our atmosphere at thousands of light years, are caused by superluminous supernovae (aka hypernovae) and weaker GRBs like the ones we usually see are caused by type 1c and 2b/n supernovae, although it is unclear whether they are different or closely related to hypernovae. The latter create long duration gamma ray bursts which last a lot longer than the usual burst and carry significantly more energy.

I hate saying stuff like this but this blew my mind.

700 years would be twice light speed; at 0.5c it would be 3000 years.

The math is wrong but not quite in the way you figure it. His point was that if the spaceship launched at the same time as the light left and the spaceship was traveling at 0.5c. So it would be 1480 years again (1/0.5 * 1480 - 1/1 * 1480).

Depends on how long ago "they" developed telescopes capable of viewing Earth with good resolution. We know in principle how to build such instruments.

"They" may have watched the Romans build roads and sussed out their mining activities from atmospheric spectroscopy. Or much earlier, signs of agriculture.

In which case they could be here...right about...just a sec, somebody's at the door....

My post was under the assumption it wasn't an alien lifeform. If that's what the person I responded to meant, then I see his/her point better. Still, if we finally found life, I'd prefer for them to be close rather than far.

Curiosity killed the cat, but I'd rather learn about the aliens (if they are indeed arriving on our doorstep soon) than know they're too far away for either of us to make it in time.

So we could find out about it even later? :)

In her TED talk [1] Tabby explains how comets could be an explanation for this phenomenon, she even says that it is consistent with their observations, but then she goes on to say "but it 'feels' a little contrived". Sorry what did I miss here? I thought we were discussing science and coming up with theories that support our evidence using data, how does feeling fit into this picture?

Why would it be so unlikely that a big comet swarm happens to be between us and Tabby's star, a distance of 1500 light years!

Comets seem like a pretty good explanation, I haven't heard an argument against them.

[1] https://youtu.be/IyIAjUuxNKw?t=7m17s

A lot of evaluating a theory means making subjective judgements on the probability of things if there's not perfect priors established. Like debugging: You end up with things that could have a few ways of happening. Nothing seems to line up perfectly. Different team members can make arguments on what the most likely culprit is. If something doesn't feel right, then you perhaps lean towards another hypothesis.

It probably is comets, but why the comets are in the position they are in is not well described.

Science is done by people, and it is often very challenging or impossible to rigorously quantify exactly how unlikely something is. This is especially true in observational science. Furthermore, in communicating results to the public it isn't necessarily helpful to speak with quantitative rigor because the audience doesn't care. If someone says this has a 1 in a 10000 chance of being due to aliens, the headlines will scream "Scientists say alien life could be found!"

Thousands of comets in just the right spot or tens of thousands of comets over a small area just for that star which seems contrived.

If you can create a credible reason why there might be a swarm of comets like this say as remnants from a collision between a large body with just the right orbit* then that's just 1 event which is more plausible.

*And I don't mean me saying it, actually create a model that would result in it based on you know math.

I believe the comet swarm theory also rested on this being a fairly short as well as really massive and rare one-time event, which makes it rather unlikely (though obviously not impossible) that we just happen to be looking just as it happens.

It also doesn't explain the long-term dimming of the star. The alien megastructure kinda does. It's not a perfect explanation either, but from what I understand, slightly more convincing than the giant comet swarm.

You don't come up with theories using data, you test them using data. You can generate hypotheses however you like, "feeling" is a pretty common way. Semi-random guesswork is another.

Could an astronomer weigh in as to why the dimming effect isn't due to a 'rogue' blackhole entering orbit with the star and both blocking light and draining material from the star? I haven't seen that hypothesis dismissed yet.

Not entirely sure why, but I suspect because they haven't been able to determine if there's any lensing going on of the star that you'd expect to see if something like that entered the system. But I do believe that they'd see higher energy (x-ray, gamma?) bursts if it was removing material from the star which would lead to a different kind of variability. We know roughly what that should look like because of other binary systems where one star is being consumed and I don't think I've seen anyone say this looks a bit like that.

Though I'd love to have someone that's actually knowledgeable on the subject to weigh in and tell me how wrong I have this.

There wouldn't be any observed lensing because you have to be the right distance between the lens and the source for that to be observed. (For objects of comparable mass, the lens has to be roughly halfway in between the source and the observer) But if there were a black hole accreting matter from the host star, there would be an accretion disk which would be visible in X-ray.

A black hole is also too small to explain the drop in brightness. That would require something planet-sized, but a black hole is only about the size of a city.

Based on current science, there are many geometries of black holes. We can't speak in such absolutes.

Black holes are uniformly sized?

Stellar ones have a soft upper boundary. If they are so old and massive that they become planetary or even stellar sized - well the'd start drawing stealing a good chunk of the host galaxy and form their own one - with blackjack and hookers. I.e. a flickering star would be the least of your worries ;-).

What causes the soft upper boundary?

The mass of the star before it went and formed a black hole. The bigger a star, the hotter it is, and the more evaporates from the surface, and the shorter it lives. Large blackholes grow through things falling into them.

Oh I read the parent comment as black holes having a soft upper boundary. Is that the case? Or if more stuff falls in they just get bigger (minus Hawking radiation)?

So there is a complication, which is space is filled with vast amounts of nothingness. For a black hole to get bigger objects need to be on a collision course with it, which is somewhat unusual. A black hole doesn't behave any differently from the same mass as something not a black hole. So once a star turns into a black hole, the accretion disk is usually remnants/maybe more if it is in a nebula. Once that's gone, that's it for growth.

Schwarzchild radius means black holes are small. To dim the light from a star you need something very high in surface area whereas black holes by definition are the most compact objects in the universe

the star isn't distorted or emitting x ray radiation in such a way as to suggest it's within close vicinity of a black hole . A black hole is too small to block light . I'm pretty sure scientits have rule that out

more information https://disownedsky.blogspot.com/2016/02/tabbys-star-for-per...

Wouldn't that create a very regular pattern?

Anyone else thinking of the beginning of the utterly excellent "Pandora's Star" by Peter F. Hamilton?

A Bit at the scarier end of the possibility curve one hopes!


Yes, except I hated that series :)

What would it look like if a super dense object like a neutron star or black hole were feeding off the star? We only "see" those dense objects when they expel the material they were pulling in from their accretion disk as relativistic jets, right? So if an object were just leeching mass from a star but not (yet) expelling the material, would it just look like a dimming star?

This doesn't necessarily rule out aliens. It could be a post-singularity society of virtual aliens living in a quantum computer, leaching energy directly from the sun and periodically expelling waste material through relativistic jets. Of course.

I don't recall the previous discussions, but without outright ruling out possibilities for things...

* If it is some structure being built at/around the star, has anyone done the math on the rate of such a structure occluding the star from us to match the observed rate of change?

* On a similar line of reasoning, what if the star were either being drained as a power source or caught in some kind of SG1 (that stargate TV series) level disaster?

To be clear, I don't think that they're likely, but I'd rather they were eliminated for an obvious actual flaw instead of simply being unlikely.

Pretty cool that observed phenomena in space that can't yet be explained gets so much attention in the media. When you step back a bit and stop thinking about aliens

There is an epistamological conundrum involved in astronomy. In this case even Jason Wright admits that theories involving alien-action are

> a “perilous approach to science”—one > that could lead to an “alien in the > gaps” fallacy, and unfalsifiable > hypotheses.

But on the other hand, if we always strain to find a non-alien answer to everything we are in danger of making them up and distoring our ideas of what can happen naturally.

Could a extreme deforming by a another gravity corpus in a elliptic orbit reduce the pressure necessary for fusion so much that the observed luminosity drop could be explained?

It's obviously being eaten by black monoliths [1].

[1] https://en.wikipedia.org/wiki/2010:_Odyssey_Two

Could it have been hit by a large planet that lost its orbit somehow (perhaps from another system)? (And out of interest, is this an event that has been recorded before?)

Are you saying we looking the edge end of an Accretion Disk[0] ?


Two planets collide, forming a huge mess, that mess continues to collide with itself in a chain reaction. If the rings of saturn surrounded a star, what would that star look like when viewed edge on? Do the rings precess? What can we say about the size of the object in the ring and how will the ring structure evolve over time?

I think this scale-correct image pretty much answers that: https://www.wwu.edu/skywise/solar/solar3.jpg

Tabby's star is a bit larger than the sun (1.4 solar masses) but you get the idea. You would need something much larger than Jupiter to visibly impact it.

When Elon Musk and Jeff Bezos start building their mega structures around Mars, some far away alien species will report a similar sighting about us.

> dimming at such an incredible rate that it can't solely be explained by any of the leading hypotheses

So it must be aliens. That can explain anything.

Being eaten from the inside out by a black hole?

We thought pulsars were alien transmissions for a while.

how about multiple nutating disks of debris who's centres are the star in question.

Maybe its the On/Off star

The dimming is probably a dark matter nebula passing between it and us.

Dark matter, by definition, does not interact with light. Therefore, it cannot cause the dimming.


> The name refers to the fact that it does not emit or interact with electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum.

Couldn't it bend the light enough that it looks to be dimming to us?

Gravitational lensing has pretty distinct other characteristics that would be noticeable.

Would plasma cosmology explain this?

Not in the slightest.

> In the meantime, we would remind you that it's very, very unlikely that this strange flickering star has anything to do with aliens (and is even more exciting if it doesn't - because, hello new space phenomena!).

I think aliens would be a little bit more exciting... Might just be me though.

that headline though ?, online journalism at its worst, the chase for clicks, there really needs to be some solution to this problem journalism is dying and clickbait is where is at.

"Extraordinary claims require extraordinary evidence", and this is the weirdest star we've seen. Your claims of clickbait are out of line, because we really don't know and alien megastructures is a reasonable theory.

And 'alien megastructures' isn't even the most ridiculous idea: https://www.reddit.com/r/KIC8462852/comments/4w7qfi/ben_mont...

That can't physically work: for one because the parallaxes would be different and almost never line up. If something's colinear with a star today, it won't be colinear 6 months later, when the Earth's on the other side of the sun.

At 2 light years for instance, that spacecraft would trace an apparent ellipse 3.3" in diameter, while Tabby's star (1,480 ly) would be stationary (0.004" parallax). In comparison, the star's apparent disk is just 30 μas wide (0.00003").

This is an amazing theory. What could possibly be more out there than alien life? Alien life in a gigantic spaceship accidentally coming between you and a star.

Would it actually be a straight line?

Going from e.g. Earth to Mars does not consist of aiming for Mars and firing your rockets. It consists of hitting a parabolic transfer orbit and then doing another burn to place yourself in Mars' orbit -- or just heading right in if you've got the heat shields and retropropulsion for that. Basically you do orbital mechanics like Wayne Gretzky: you don't go to where the planet is, but where it's going to be.

Would interstellar flight be that different? Wouldn't you be executing a "transfer orbit" about the galactic center? Or is the effect of galactic-scale gravitational pull negligible there and you just end up basically going straight from A to B?

Edit: turns out this came from an actual subreddit dedicated to this star!



The galactic center is 100,000 lightyears away. Going from a location to another 1000 lightyears away via the galactic center would make the trip 200 times longer. A 10,000 year journey would thus take 2 million years. It's probably better to jump from point A to B, then.

no, @api is right - you're orbiting the galactic center for a while.

Similar how transfer from earth to mars works via a solar orbit.

So, yes, you have to include orbital mechanics, not just straight lines.

I didn't say there's no need to consider orbital mechanics. I said taking a route through the galactic center is not a realistic scenario.

I didn't mean through the center, just orbiting it. Look up a Hohmann transfer. I was just saying it wouldn't be direct.

Would it be "accidental" if they were traveling in a direct vector approaching us?

Incredibly implausible idea for the sheer improbability, but fun to imagine nevertheless.

I would think that by the time they actually move some meaningful distance, their sun would not be 'behind' them anymore, they'd still be moving toward ours, but as the whole thing is constantly moving, their sun would have moved relative to ours.

I think a big part of the answer is not to care. Or rather to just silently auto-discount.

Imagine the 60s-90s and advertising just overwhelm with sexualised figures. We don't notice, because we just silently pass by.

I don't see any way of turning back the tide of hyperbolic titles on articles. Better to just ignore them and move on.

Buzzfeed headlines worked on me the first few times, now I know not to go there.

Yeah, this is what I do to a tee. I just say "well, can't credit them as a reliable source of quality journalism." Then I move on and find some coherent research on what I need to know.

Lets brainstorm.

Perhaps one mathematical solution to the problem is to score pages based on the average time spent for each article. My hypothesis is that clickbait articles will score very low because the article will attract a lot of clicks from people who are not interested in the actual content but only the headline.

In theory, you could do this by deploying a tracker across the web similar to a Google analytics that performs the measurement. But in practice, of course, this isn't possible.

You might be able to approximate the score by building a browser extension that makes the measurement. A browser extension might also a good way to output results. It could, for instance, colour-code links (on mouseover) to help you spot click-bait before you click it!

There's a plugin for Wikipedia where if you hover over a linked term, it will show the first paragraph from that article, usually all you need.

We just need something like that for the web.

I like your solution because it doesn't (necessarily) require a backend and would therefore be much simpler to implement.

There are several libraries that extract article text reasonably well. I believe browser extensions are written mainly in HTML/JS/CSS. Would the following node library suffice? https://github.com/ageitgey/node-unfluff

There's just the question of retrieval speed. I suspect simple HTML retrieval is an order of magnitude faster than normal page rendering due to ads, javascript, etc. So the client-only solution you've proposed might indeed be sufficient!

I use QuickLook in Safari on OS X and iOS like that (OS X: triple-finger-tap to get a link preview, iOS: Force touch). It only gets ruined by those "subscribe!" full screen popups.

I hope one day title bashing turns into a global no-ads movement.

A global "we pay for the content" movement? Would be interesting.

FB is working on this. If misleading title > lower ranking score.

Please correct the title, it is about a Tabby's star, not alien megastructures.

Thanks, we updated the title. We're happy to change it again if someone can suggest a better one.

Pancreator deliver us, the suns fade.

More accurately - it dimmed at an incredible rate ~1480 years ago and we are just now seeing the light from that event.

Registration is open for Startup School 2019. Classes start July 22nd.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact