Tabby's Star | Hacker News Reader

Tabby's Star

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88 pointsbenbreen63 comments

TED talk: Tabby talks about her star. (2016) https://www.ted.com/talks/tabetha_boyajian_the_most_mysterio...

Something massive, with roughly 1,000 times the area of Earth, is blocking the light coming from a distant star known as KIC 8462852, and nobody is quite sure what it is. As astronomer Tabetha Boyajian investigated this perplexing celestial object, a colleague suggested something unusual: Could it be an alien-built megastructure? Such an extraordinary idea would require extraordinary evidence. In this talk, Boyajian gives us a look at how scientists search for and test hypotheses when faced with the unknown.

I actually believe that if we detect spacefaring aliens, it will actually be from events like this. There's a lot of thought that has gone into this. Basically, a natural evolution seems to be to build Dyson Swarms. There are lots of reasons for this, most notably the efficiency in creating living area (per unit mass) compared to planets and the "free" energy.

A consequence of this is such a megastructure would have high IR emissions. Why? Because in space the only way to cool off is to radiate heat away. That wavelength of that radiated heat is determined by the temperature of the radiating object. For any normal temperature we'd expect to see, that means IR radiation.

The Tabby's Star dimmings seem to have the opposite behaviour: very low IR emissions. This is a pretty strong suggestion that it isn't artificial in origin.

Forgive me for asking a potentially silly question, but wouldn't the heat dissipating via IR be also seen as wasted energy? I understand that at our current level of physics, to do anything less would involve catastrophic heat build up but I would suspect an alien species capable of building a Dyson Swarm to have access to other means of keeping the temperature stable whilst leaving very little energy to go to waste.

There are thermodynamic limits to how efficient solar energy can be. It's almost inevitable that a sizeable portion of the energy will get lost as heat.

That may be the case, but why would it radiate on the non-star facing side? Take the JWT for example: no-one looking back at that would see anything higher than -50 degrees Celsius.

If the point was to capture energy then anything radiating from the non-star facing side suggests inefficiency.

Even if the solar energy has limits, why wouldn't they use waste heat to support, say, plant growth?

Not that I think it is a mega-structure, it's just it doesn't strike me as lack of IR emissions as being that informative.

The JWT is a perfectly good example of this, it's not hot compared to the sun but it's way hotter than the cosmic background. And that's if you're just reflecting light back to the sun, when you try to extract meaningful work from it you'll have to absorb a lot more energy.

My favorite example of how an alien civilization could send signals out to the neighborhood is just to put a really big triangle in orbit around their star. Anyone monitoring the brightness of the star for planets would get a real surprise by the signature it puts in their data.

Does it suggest a natural origin, or just that it isn't likely to be a Dyson swarm?

"It has also been hypothesized that the changes in brightness could be signs of activity associated with intelligent extraterrestrial life constructing a Dyson swarm; however, further analysis based on data through the end of 2017 showed wavelength-dependent dimming consistent with dust but not an opaque object such as an alien megastructure, which would block all wavelengths of light equally.[17][9][19]"

Fun, to think about, and who's to say the Dyson Sphere isn't somehow transluscent, but this sounds like pretty good evidence to my pea brain that we're observing a non-Dyson Sphere object. Definitely exciting candidate target though and I'm happy we keep searching for our celestial cousins.

Unless the dark forest [0] theory is correct and the Dyson Sphere is designed to look to all intents and purposes like a dust cloud.. (not that it helps us with our discovering).

0: https://en.wikipedia.org/wiki/The_Dark_Forest

I was confused by that statement and the sibling comment that a Dyson swarm would block visible light but not IR and Tabby's star seems to dim in IR. So is it dimming all wavelengths or not? Is it dimming some visible (but not all) and IR?

> would block visible light but not IR

It would not block some spectrum of IR, probably at the far IR region. Compared to a star, it should probably emit much less near visible IR. It depends on what temperature the aliens prefer, but I wouldn't expect anything similar to a star's emissions.

Anyway, there exist telescopes tuned to far IR. I don't know what kind was used on that observation.

It's not that it wouldn't block IR from the star. It's that they would radiate waste heat as IR.

I was one of the Kickstarter backers to investigate this further. I got a nice t-shirt and some stickers, but I was just interested in what we would find out. We certainly managed to fund further observations, and rule out some of the theories.

Hasn't been any updates for quite a while now though.

According to John Michael Godier there is some new data available: https://www.youtube.com/watch?v=zSCN09SSRck

Very interesting, thanks!

The mystery deepens. More candidate stars showing the same dimming, and all clustered in space around Tabby's star, and of the same stellar types.

Doesn't mean aliens, but it's certainly provocative.

I wonder how much of the visible sky it’s affecting from our vantage point. Ie how sure are they that it’s not a near field obstruction?

The video says they would expect other stars to be obscured if the effect wasn't localised to those star systems.

You will the distribution of current candidates in the sky on page 6 of this paper cited in the video comments [1]

[1] https://arxiv.org/pdf/2111.01208.pdf

Thanks. Says that "While a probability at this level is not generally considered to be highly significant, it does suggest that the clump is real."

I'd never heard the term "citizen scientist" before. What's really weird is it's apparently a group that includes Darwin and Newton! I would just call them scientists or perhaps amateur scientists/astronomers.

The term refers to "amateurs" in the sense that they did not study at a university or get a degree. AFAIU, the term "citizen" is preferred because "amateur" these days carries a connotation of "doesn't know what they're doing", while citizen scientists have made (and continue to make) meaningful contributions to astronomy. (Possibly other fields, too, but I don't know one way or the other.)

Darwin and Newton were subjects, not citizens. One of the reasons I hate the "citizen scientist" moniker: it conflates republicanism, a political system for struggle between states, with science, an intellectual endeavor that transcends the boundaries between states and between centuries.

So many mysteries out there. I can't wait until Webb starts beaming back data and is fully operational.

I can only imagine what we'll learn from it.

Can webb even point at tabby's? Ive never seen a strait answer on this, but i think webb's sunshield arrangement limits it to objects away from the ecliptic, which is fine if you are looking at stuff outside our galaxy.

I've been curious about this as well and decided to look it up; there's a nice video that shows it off fairly well[1]. The sunshield is perpendicular to the light coming from the sun, as is the view from the telescope, though the sunshield is large enough that it can be off several degrees and still keep the telescope in shadow. You can rotate the telescope about that axis and remain perpendicular to the sun allowing a 360 degree view forming a plane. As it orbits around the sun that plane is hitting a different slice of the sky so over the course of 6 months you can view everything.

[1] https://webbtelescope.org/contents/media/videos/1157-Video

That explains the contradictory statements I've seen over the years. The program can view the entire sphere over a period of a year, but at any one moment the telescope only has access to see stars within a particular plane. So it isn't available for ad hoc targeting of interesting things as they happen (nova, transits etc) unless they are in the plane of available options at that moment.

That also meshes with the cultural issued behind the scenes. JWST has always been more of an stellar astronomy and cosmology instrument. It won't be much use in looking at closer/moving things like Oumuamua or phenomena like Tabby's star transits that occur at very particular times. So it isn't an instrument for so-called "planetologists", which is the hot field in modern astronomy but was barely a thing when JWST began.

Of course JWST is an instrument for studying exoplanets (among other things). Something like 24% of the first year’s approved observing proposals are for doing just that. There are coronagraphs in two of the main instruments, all specifically meant for exoplanet observations.

https://eos.org/features/overture-to-exoplanets

Exoplanets are one type of planet and their detection is really just a subset of stellar astronomy in that it relies on stellar instrumentation. The hot stuff these days is within the solar system, especially since since the Pluto flyby. Minor plants, planet X, extra-solar objects (Oumuamua) and the hunt for life within our solar system ... these are the big areas of public interest in the next decade and will be the focus for planetology (I still cannot say that without thinking of Herbert).

OK, you're really not making much sense. I mentioned exoplanets because that was a (barely) plausible interpretation of something that was a "hot field in modern astronomy but was barely a thing when JWST began", since the preliminary studies for JWST did happen in the mid-1990s, when exoplanets were first beginning to be found. The actual serious design work, though, was in the early 2000s, when exoplanets were definitely a hot topic.

But if what you really mean is "within the solar system" (which, um, excludes "Tabby's star"), well... "barely a thing when JWST began" is complete nonsense. I mean, studying things within the solar system is something astronomy has been doing for literally thousands of years. (And, no, it hasn't suddenly become "the hot field" in any sense, leaving aside the point that there are multiple things that might be considered "hot fields" at the moment, and that there's never a single "hot field" anyway.)

JWST is perfectly useful for solar-system science: there are about 22 approved Cycle 1 General Observer proposals in that field, including one specifically meant for any "interstellar object" (like 1I/'Oumuamua or 2I/Borisov) that might show up during the first year: https://www.stsci.edu/jwst/phase2-public/2337.pdf

And the second-largest set of Guaranteed Time Observation proposals (proposals from "scientists who helped develop the key hardware and software components or technical and inter-disciplinary knowledge for the observatory"), after "Extra-solar Planets", is "Solar System": https://www.stsci.edu/jwst/science-execution/approved-progra...

Webb can 'see' everything but objects between Webb's location and the sun. At each moment, it's limited to part of the sky, but over a whole year, it can observe in all directions.

It's constrained to about 10 degrees in the roll axis, 50 degrees in pitch (-5 to +45), 360 in yaw. At any given moment, it can point anywhere in about 39% of the full sky (inner solar system excluded of course), but can access the entire sky over a period of 6 months.

see: https://jwst-docs.stsci.edu/jwst-observatory-characteristics...

Or in video form: https://www.youtube.com/watch?v=y0bOi3kVIBs

Perspective is funny. When I think of it hanging out there in space I think of it as having 360 in roll. But I guess if you were facing in the direction of the mirror that would be 360 in yaw.

yeah, really depends on the coordinate system you use but to me it's like a square-rigged ship with the sunshade as the hull, the tower as mast, and the main mirror as sail.

And it's consistent with the terminology used to describe parts of the sunshade during deployment -- fore/aft sunshield pallets, port/starboard sunshield booms..

As someone not involved in the field, I have always gotten the impression that all the major questions are settled, the processes are understood and that the work being done by active astronomers is really only at the margins, fleshing out the details in a word. And I think that's a view often promoted by scientists and the popular press, for the reasons that we have gained a tremendous understanding of the univers over the past 500 years, heck over the past 50 years, and no one wants to focus on talking about what we don't understand.

And then you see stuff like this and Oumumamua and its exciting and interesting and then you begin to realize that there's tons of stuff we really have no idea about, that at best we can make plausible explanations and try to rely on Occam's Razor and parsimonous assumptions.

I wish there were more of this because I find it delightful and inspiring.

I think there is something to this.. possibly as a side effect for how knowledge is distributed. We are told about the discoveries and the things we found out. We are not told about everything else there is yet to discover, partly because its mostly unknown unknowns.. and it takes a fair bit of digging just to find out what the current big unsolved mysteries are. It's like the more you know the more you realize you don't know. I think it would greatly benefit all of us if we found a way to focus more on what we don't know.

Well current mainstream cosmologists claim they literally don't know what 80% of the universe is made up of (that's why "dark" matter). So...

It’s funny — that’s a pet peeve of mine too. To read the popular press you don’t get that impression at all. In fact it’s all authoritative statements about the “best map of far matter yet” or some other conclusion about dark matter. And if (for instance in the comments section of HN) one brings up the fact that they have no idea and dark matter is just a plug between what we know about gravity and what we observe in the EM spectrum, one often gets shouted down.

>> I have always gotten the impression that all the major questions are settled

This is unfortunate- feels like that mindset could stifle innovation

I like the name “WTF Star”.

Which stands for What The Flux, obviously ;-)

> In December 2018, a search for laser light emissions from Tabby's Star was carried out using the Automated Planet Finder (APF), which is sensitive enough to detect a 24 MW laser at this distance.

But why? It’s intriguing, I just wish they could say what the hypothesis was. Alien teens goofing off pointing laser pointers on passing flying saucers?

I think you are miss-interpreting this. I think they mean it can detect a source of light as small as a 24MW laser.

So if there is a planet, or any other object orbiting the star it is very likely to be picked up by this instrument.

Presumably attempts to communicate with the earth. If we can see them, they can certainly see us.

They almost definitely can't see us. It's 1470 light years away, the light they are seeing now left earth in 650 AD, there wouldn't be much to see, at least assuming the presumed ETs can detect EM transmissions and analyze the earths atmosphere but not directly observe the surface with any appreciable resolution.

The underlying theory behind the SETI interest is that we are seeing the effects of 'alien megastructures' in orbit around that star. If they can build that, presumably they would be able to build scientific instrumentation to characterize the planet if not directly image it.

I think his point is more that -- given the speed of light -- it's extremely unlikely that there is anything to see from us in...650AD which is what would be arriving there right now.

Is there any reason for our planetary system to attract attention? It's too far away for our radio transmissions to have attracted attention. Not sure there's anything unusual about us that would warrant attention from a distance.

It's a rocky planet in the 'goldilocks' zone that is flickering with the spectral fingerprints that indicate life is present and flourishing.

Within a hundred years we'll almost certainly be directly imaging exoplanets within 10-20ly. A thousand years from now it seems plausible we'll have a good catalog of the interesting ones.

Not necessarily attempts to communicate with Earth. Aliens might be using beamed propulsion for solar sails, for example.

This is probably the only good reason I can think of why they might point a laser directly at us. They have no idea we're here, listening. The chances that we happen to be listening at exactly the right moment is miniscule. For the same reason, I don't have a lot of hope that SETI using radiotelescopes will ever find anything. But using lasers to power a ship or probe headed to our solar system could make sense.

Well, maybe not from Tabby's Star; it's over 1000 ly away. I'm sure they have plenty of closer targets to send their probes to.

Also just powering craft in their own system, doesn't have to be interstellar targets. See this post for an interesting take on how we could use it in the solar system.

https://www.centauri-dreams.org/2022/01/11/interstellar-reac...

Yeah, but then what's the likelihood of aiming directly at us? Even a fraction of a degree off and we won't see it.

If you have a decent understanding of the planets in a system you could potentially time your observations to when planets are in alignments that would beam lasers / radio waves your way. It's possible that you could pick up directed in-system communications that are overshooting their destinations rather than broadcasts intended for potential interstellar neighbors.

I'd say higher for intra system craft, as you'd expect a much higher volume of such craft pointing at a greater number of targets at different orbital positions than interstellar targets.

>I'm sure they have plenty of closer targets to send their probes to.

And perhaps they already have: https://arxiv.org/pdf/2111.01208.pdf

It doesn't have to be directly at us, there is a misconception that lasers don't spread, but they do, the inverse square law even still applies to them at big distances.

I guess our light spectrum implies water and complex hydrocarbons. A surely important object of study, from intelligent aliens.

Tangentially related: There's a Vernor Vinge novel called "A Deepness in the Sky" in which a star called OnOff cycles over a multi-year period between normal brightness and emitting no energy at all. Much of the novel has to do with the adaptations of species on the star's planets.

Wow, 1470 light years distance. Even at warp 9, it will take over a year to get there!

At least it's still in the Alpha Quadrant.

A slow burning sub to go with it - https://old.reddit.com/r/KIC8462852/

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