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Boyajian's Star ("Tabby's Star"): Odd Dimming; Alien Megastructure?

One thing I've never seen discussed in adequate detail is where does the material to build a dyson sphere come from?
In the Solar System the combined mass of all the planets and asteroids, etc, only amounts to a fraction of a percent of the mass of the sun. But a dyson sphere around the sun would have to be many times larger than the sun, and even if it's a relatively thin shell it would still amount to a huge mass in total.

Dyson himself said, "A solid shell or ring surrounding a star is mechanically impossible. The form of 'biosphere' which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star." He also wished that the concept of a Dyson Sphere had not been named after him!
https://en.wikipedia.org/wiki/Dyson_sphere
 
rynner2 said:
One thing I've never seen discussed in adequate detail is where does the material to build a dyson sphere come from?
In the Solar System the combined mass of all the planets and asteroids, etc, only amounts to a fraction of a percent of the mass of the sun. But a dyson sphere around the sun would have to be many times larger than the sun, and even if it's a relatively thin shell it would still amount to a huge mass in total.

Dyson himself said, "A solid shell or ring surrounding a star is mechanically impossible. The form of 'biosphere' which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star." He also wished that the concept of a Dyson Sphere had not been named after him!
https://en.wikipedia.org/wiki/Dyson_sphere
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I missed this post earlier, because I was on holiday.

There are quite a few options for constructing a Dyson Sphere, and they don't all require vast amounts of mass. In fact the lightest option is a swarm or bubble of lightweight material, supported by starlight. Light pressure can support a sufficiently thin film of material against gravity, creating a so-called statite;
https://en.wikipedia.org/wiki/Statite
If you wanted to surround the Sun with statites at a distance of 1 AU, the total mass of material would be about the same as the asteroid Pallas.
https://en.wikipedia.org/wiki/Dyson_sphere#Dyson_bubble
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But maybe you want to build something a bit more substantial. You could disassemble the planets and asteroids - this would create a shell 8-20 centimetres thick, but it would collapse immediately under gravity. The same material could be assembled into a swarm, which would allow some light through but would be readily detectable.
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The late Paul Birch suggested another source for material that most people overlook - the Sun itself. A Sun-like star contains a non-trivial fraction of metals and other elements, far exceeding the solid mass of the solar system; using the light of the Sun for power, it could be possible to extract some of this material for building purposes.
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Or you could start with a star that was already surrounded by dust- a star like Tabby's star, for instance, is surrounded by vast amounts of material in dust form, most of which is lost later during the process of planetary formation. Tabby's star probably isn't a Dyson swarm, but if you wanted to build one, it would be a good place to start.
 
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More WTF (Where's The Flux) from Tabby's star, now misbehaving while some telecopes are pointed at it!

Video interview about it with Tabby below:

 
Maybe it's a quantum star? If we look at it, we are interacting with it...
 
Tabby's Star Dimming 'Probably Dust'

According to a new study published in the Astrophysical Journal, a cloud of cosmic dust may be orbiting the star roughly every 700 days - causing the light from the star to dim periodically.

Observations showed that the star's ultraviolet light was dimming more than its infrared light.

Huan Meng, lead author of the study at the University of Arizona, Tucson said: “This pretty much rules out the alien megastructure theory, as that could not explain the wavelength-dependent dimming."

The team used two NASA telescopes to watch Tabby's Star (officially known as KIC 8462852) from October 2015 to March 2017 in order to measure the UV and infrared dimming.

“We found that from UV, throughout the visible spectrum, to IR, the star is dimming at every wavelength we monitored,” said Dr. Meng.

“It cannot be anything from the interstellar medium.

“Only microscopic fine-dust screens are able to scatter the starlight in the way characterised by measurements.”
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There's a new hypothetical explanation for Tabby's Star's weird dimming behavior - a disintegrating / melting ploonet (minor not-quite-planet; possibly an errant moon).
There's a New Explanation For Mysterious Tabby's Star: A Melting Ploonet

We're yet to make a conclusive detection of an exomoon. But if such moons are out there, orbiting planets outside the Solar System, one of them could be responsible for the peculiarities of KIC 8462852 - AKA Tabby's star.

New research suggests that the strange brightening and dimming fluctuations of the star's light that have been observed for years (and back-traced from archival data) could be the result of a disintegrating exomoon in orbit around the star.

Such a wayward moon - recently nicknamed a ploonet - would be shedding dust and chunks of rock that move between us and Tabby's Star in a coalescing disc.

Tabby's star, a yellow-white dwarf star located around 1,280 light-years away, was discovered in 2015, and since then it's been a real head-scratcher. Its dimming is completely random. The depth of the dimming varies, too - it's dimmed by up to 22 percent, and last year was caught dimming by just 5 percent.

This behaviour pretty much rules out planets; when an exoplanet passes between a star and Earth as it orbits, it will dim the star by a tiny amount - 1 percent or less - at regular intervals.

In addition, the star's overall brightness seems to be fading over time; between 1890 and 1989, archival data revealed, it faded by 0.193 magnitude.

Follow-up observations have revealed that some wavelengths are blocked more than others, which wouldn't be the case with an opaque solid object (like, for instance, an alien megastructure).

The star is thought to be too old for any remnants of a stellar accretion disc to still be orbiting; in any case, analysis has ruled out a high abundance of close material orbiting or falling into the star.

Some sort of dust or a swarm of comets that absorbs some wavelengths more effectively seems to be the most plausible explanation, but it would have to be an insane amount of dust or comets.

Where could that material come from? According to researchers at Columbia University, there could be a fitting answer: an orphaned exomoon, separated from its planet and slowly melting, shedding dust and debris that ends up orbiting the star in a clumpy cloud. ...
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FULL STORY: https://www.sciencealert.com/a-new-explanation-for-tabby-s-star-a-melting-ploonet
 
Here's another article about this new research ...
Rogue Ice Moon Could Be Spilling Its Guts All Over 'Alien Megastructure' Star

Back in 2016, headlines all over the world blared with news of a possible "alien megastructure" detected orbiting a distant Milky Way star. Now, a team of Columbia University astrophysicists has offered up an explanation for the star's strange behavior that doesn't involve any little green men. ...

Astronomers have since offered a number of alternative explanations for the weird light from the star, which is about 1,500 light-years away in space and known formally as KIC 8462852. They range from swarms of comets to "avalanche-like magnetic activity" within the star. Boyajian conducted follow-up research that showed that the dimming is specific to certain light frequencies, which could be explained if a cloud of dust were responsible, scientists have suggested. This new research explains how that dust might have gotten there.

The new theory from the Columbia team resembles the plot of a disaster film more than a science-fiction space opera. They built on earlier work showing that whatever's causing the dimming is likely locked in an irregular, eccentric orbit around the star. They showed that a disintegrating, orphaned ice moon following such a path could explain the strange dimming. ...

"It's likely outgassing water or some other volatile material," said Brian Metzger, one of the authors of the new paper.
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FULL STORY: https://www.livescience.com/icy-moon-alien-megastructure-star.html

DRAFT PrePrint Version of the Paper:
https://arxiv.org/abs/1906.08788
 
An astronomer has been surveying past data repositories to determine whether Tabby's Star is unique. It isn't ... The first tentative survey identified 21 stars which seem to display similar dimming behaviors, albeit with different frequencies and intensities.
'Alien Megastructure' Star Not Alone. More Mysteriously Dimming Objects Found.

A mysterious star whose repeated bouts of darkening might be due to "alien megastructures," according to some researchers' conjectures, may now have more than a dozen counterparts that display similarly mystifying behavior, a new study finds.

Further research into all of these stars might help solve the puzzle of their bewildering flickering, the study's author said.

In 2015, scientists noticed unusual fluctuations in the light from a star named KIC 8462852. This otherwise-normal F-type star, which is slightly larger and hotter than Earth's sun, sits about 1,480 light-years from Earth, in the constellation Cygnus. ...


When the researchers analyzed data from NASA's Kepler space telescope, astronomer Tabetha "Tabby" Boyajian, then at Yale University, and her colleagues found dozens of odd instances of KIC 8462852 dimming by up to 22%, with such dips lasting anywhere from a few days to a week. These events did not appear to follow any pattern and seemed far too substantial to be caused by planets or dust crossing the star's face.

These analyses of KIC 8462852 — now nicknamed "Boyajian's star" (formerly Tabby's star) after its discoverer — raised the possibility that astronomers had detected signs of intelligent alien life. ...

The megastructure hypothesis is near the bottom of most astronomers' lists these days when it comes to Boyajian's star, however; further analyses have pointed to more prosaic explanations, such as clouds of dust or comet fragments. ...

Now, study author Edward Schmidt, an astrophysicist at the University of Nebraska-Lincoln, suggests that he may have discovered more than a dozen stars like Boyajian's star. ...

Schmidt looked for counterparts of Boyajian's star using software that searched for analogous dimming events from about 14 million objects with varying brightness monitored in the Northern Sky Variable Survey from April 1999 to March 2000. He then followed up on promising candidates by examining their long-term behavior, using data from the All-Sky Automated Survey for Supernovae, ruling out sources whose dimming could be caused by conventional explanations such as an eclipsing companion star or some intrinsic variability in brightness.

Schmidt identified 21 stars that showed possibly unusual dimming. These fell into two distinct categories: 15 were "slow dippers" that dimmed at rates similar to Boyajian's star, and six were "rapid dippers" that showed even more extreme variability in their dimming rates.

"The thing that surprised me the most were these stars that had so many dips, the ones I called 'rapid dippers,'" Schmidt told Space.com. "I expected more occasional dips like Boyajian's star."

Further analysis using data from the European Space Agency's Gaia space observatory found that these potential dippers tended to be either conventional "main-sequence" stars with about the same mass as the sun or red giant stars with about twice the sun's mass. The slow and rapid dippers are seen in both groups, which may suggest that they represent varying degrees of the same mechanism, Schmidt said.

Schmidt noted that the Northern Sky Variable Survey he searched for potential counterparts of Boyajian's star did not contain records of Boyajian's star itself darkening during the year of data in that catalog. This highlights how astronomers may easily miss stars that can darken in this manner if they look only at catalogs that monitor stars for relatively short intervals of time.

"We're obviously missing some of these stars because of the catalogs we have," Schmidt said. "By looking at more catalogs, we may get a better picture of what's going on, even though it won't be a complete picture."

Future research that combs through more catalogs of stellar activity may turn up even more analogues of Boyajian's star, he said.

"I intend to try and follow up on the rapid dippers," Schmidt said. "One thing I noticed about them is that at least one seemed to be slowing way down in its dipping rate over the five years of coverage we have of it. It'd be interesting to find out what happened in its past, which may help give a better idea of what's going on with these stars."

Schmidt detailed his findings July 18 in The Astrophysical Journal Letters.
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FULL STORY: https://www.livescience.com/alien-megastructure-mysteriously-dimming-stars.html
 
Here's the publication data, abstract, and URL for the article describing this new survey work ...
A Search for Analogs of KIC 8462852 (Boyajian's Star): A Proof of Concept and the First Candidates

Edward G. Schmidt1
The Astrophysical Journal Letters, Volume 880, Number 1

Abstract
The seemingly normal F dwarf, KIC 8462852 (a.k.a. Boyajian's Star), has been observed to exhibit two types of behavior unique among known variable stars: infrequent episodes of small brightness dips and a long-term decline in brightness between the dips. No satisfactory mechanism has been found for this behavior, at least in part, because there is only one known example. To begin to rectify this, we have searched for other stars exhibiting similar dipping behavior using the Northern Sky Variability Survey and have used data from the All Sky Automated Survey for Supernovae to further investigate the behavior. Twenty-one stars are identified as possible dippers. Fifteen may be similar to Boyajian's star and the other six are likely to be more extreme examples of the same phenomenon. Using data from the Gaia Second Data Release we show that the dipper candidates are located in two restricted regions of the H-R diagram, near the main sequence with masses near 1 solar mass and in the red giant region near the evolutionary track for 2 solar mass stars. Stars in the former group are considered to be likely analogs to Boyajian's star and should be studied in more detail to gain insights into the dipping phenomenon.
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FULL ARTICLE:
https://iopscience.iop.org/article/10.3847/2041-8213/ab2e77
 
EnolaGaia said:
Here's the publication data, abstract, and URL for the article describing this new survey work ...


FULL ARTICLE:
https://iopscience.iop.org/article/10.3847/2041-8213/ab2e77
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With the current theory being that the star is vaporizing and eating an exomoon, it seems interesting that the other identified dipping stars are clustered into two types, presumably many star types would have planets/exomoons to vaporize and cause this type of behavior.
 
kamalktk said:
With the current theory being that the star is vaporizing and eating an exomoon, it seems interesting that the other identified dipping stars are clustered into two types, presumably many star types would have planets/exomoons to vaporize and cause this type of behavior.
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The universe is famously big: it's only a matter of time before we encounter multiple examples of even rare phenomena.
 
James_H said:
The universe is famously big: it's only a matter of time before we encounter multiple examples of even rare phenomena.
Click to expand...
I'm not surprised that they found more examples, I'm surprised that the additional examples they found were clustered in two specific star types instead of being more random given the suspected reasons for the behavior.

"Further analysis using data from the European Space Agency's Gaia space observatory found that these potential dippers tended to be either conventional "main-sequence" stars with about the same mass as the sun or red giant stars with about twice the sun's mass. "
 
New research suggests Tabby's Star (Boyajian's Star) may have a binary companion - something that might well explain the star's mysterious dimming behavior.
The Mysterious 'Alien Megastructure' Star Is Not Alone, Astronomers Discover

A new clue has just been found that could help solve the mystery of a weirdly dimming star. KIC 8462852, also known as Boyajian's Star, seems to have a binary companion that could be contributing to its irregular dips in brightness.

If confirmed with more detailed observations, the newly discovered companion star could help astronomers finally solve KIC 8462852's ongoing mystery. ...

The presence of a binary companion star on a wide orbit could help explain the presence of all this material, providing additional gravitational perturbations to disrupt orbiting bodies. ...
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FULL STORY: https://www.sciencealert.com/boyaji...omers-have-just-identified-a-binary-companion
 
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