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Thread: Alien megastructure?

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    Senior Member Adam Bomm's Avatar
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    Re: Alien megastructure?

    Can We Explain the Curious Case of Tabby’s Star?
    By: Alex Green | June 9, 2017
    33
    Three new ideas have emerged to explain Tabby's Star, officially known as KIC 8462852, but the jury's still out on what's really causing the weird behavior of our galaxy's most mysterious star.

    Comet swarm around Tabby's Star
    This artist’s concept shows a swarm of comets passing before a star.
    NASA / JPL-Caltech
    The star KIC 8462852, also called Tabby’s Star, has been the subject of intense debate since May’s announcement that this unusual F-type star, located in the constellation of Cygnus, was dimming once again.

    Observations at Fairborn Observatory detected a 2% drop in brightness between May 19th and 21st, and a host of ground- and space-based telescopes jumped in on the action.

    Ever since the first public report of the mysterious star in 2015, numerous theories have been proposed to explain its bizarre behavior — sometimes the star’s brightness dims by a couple percent, like last May, but sometimes it dips by as much as 20%, and for days to weeks at a time. Not to mention the long-term fade that appears to be plaguing the star. So it’s no surprise, perhaps, that many proposed explanations have failed in their attempts to explain what’s going on.

    “Most of [the theories] seem pretty contrived to me, if not completely crazy,” says Richard Larson (Yale University).

    However, in the weeks since the most recent event, a few hypotheses have emerged that stand out as genuine contenders able to explain this cosmic mystery.

    Trojan Asteroids Around Giant Planet

    The first idea comes from Fernando Ballesteros (University of Valencia, Spain) and colleagues. In a paper posted to the arXiv preprint server, the team proposes that a large planet orbits KIC 8462852, complete with a set of rings as well as two massive clouds of Trojan asteroids ahead of and behind the planet in its orbit. The team suggests that the deepest drops in the star’s brightness are a direct result of these objects.

    Diagram of Trojan Asteroids around Tabby's Star
    This diagram shows the setup of the scenario put forth by Ballasteros and colleagues: a giant planet with a giant system of rings orbits Tabby's Star, accompanied by two swarms of Trojan asteroids, trailing and leading the planet in its orbit. Below, the light curve shows how the brightness of KIC 8462852 would change as the various objects in the system pass in front of the star.
    Ballasteros et al. arXiv
    Coauthor Pablo Arnalte-Mur (University of Valencia, Spain) explains that he and his colleagues came to this idea by analogy to our own solar system, where we’ve found a multitude of Trojan asteroids around Jupiter and some around Mars, Neptune, and even Earth.

    However, one problem with this scenario is that the planet in question would have to be very large — about five times the size of Jupiter — which brings it into the realm of red dwarf stars rather than planets. If the planet is in an early evolutionary stage, that could explain its size, but Tabby's star appears to be a mature star, well out of any youthful growth spurts.

    Another potential workaround could be that the giant planet was born in a recent collision of objects orbiting the star. Arnalte-Mur says they are currently working on computer simulations of this solution.

    One advantage of this giant-planet scenario is that it’s testable. It predicts the onset of irregular transits of the Trojan asteroids in 2021 and another transit of the ringed planet in 2023 — a solid test that sets it apart from many other theories that have been put forward.

    Ring of Dust in our Solar System

    Martin Rees (University of Cambridge, UK), believes the next idea to be the “most plausible”: Far out in our solar system, a ring of dust left over from the Sun’s formation 4.6 billion years ago intercepts some of the light emitted from KIC 8462852.

    Jonathan Katz (University of Washington, St. Louis) noticed that the main dips in the star’s brightness were separated by about twice Kepler’s orbital period — which suggests a solar system origin.

    “The pattern of the irregular dips reminded me of the dips produced in a star when it goes behind one of the rings of the major planets,” Katz says.

    Katz’s theory, posted on the arXiv, suggests an uneven ring of dusty debris, with clumps spanning about 600 meters, sits at the distance of the Kuiper belt and can briefly blocks the light from the star. The orbital motion of the Kepler telescope, trailing behind Earth in its orbit, requires this obscuring cloud to be extended in just the right way along the direction of the telescope’s travel.

    Kuiper Belt
    An artist's illustration of the solar system shows the Kuiper Belt beyond Pluto, whose orbit is shown in yellow. If a dust cloud is what occasionally blocks the light from Tabby's Star, then it lies at about the Kuiper Belt's distance from the Sun, suggests Jonathan Katz.
    NASA
    Another problem also plagues the scenario: “The model should predict a clockwork-like repeatability to the dimmings, but we are seeing deviations off strict periodicity by a few percent,” says David Kipping (Columbia University). However, Katz argues that patchy rings within the cloud could still explain the observations.

    Furthermore, Kipping adds, “It can’t explain the long-term dimming of the star. It’s elegant but looks unlikely to explain the data as we presently understand it.”

    Katz disagrees: a solar-system-centered scenario has no need to explain the star’s fade over years or perhaps even decades, as that long-term trend is more likely something inherent to the star or its system.

    The Star Itself

    Another theory, which surfaced toward the end of March, came from researcher Peter Foukal, who has studied variability in our Sun’s luminosity. In a paper posted to the arXiv, he proposes that something is blocking the flow of heat to KIC 8462852’s surface. The star might be switching between methods of heat transport, for example, briefly turning off the boiling motions within the star. Or a strong magnetic field might briefly halt the star’s churning motions, creating dark starspots that could explain the dimming.

    But the deep dips observed do not match what’s expected from starspots. Moreover, in massive stars, such as the F class of stars of which KIC 8462852 is a member, heat transport from the interior tends to be more straightforward — via radiation — not dominated by the boiling motions that are more typical in smaller stars. Finally, Foukal acknowledges that understanding why the deep dips and long-term fade should be unique to KIC 8462852 requires further study.

    The quest to find the cause of the curious behaviour of Tabby’s Star continues — a quest that remains challenging as there’s just so much to explain. As astronomers from all over the world continue to observe KIC 8462852 following its recent dip, interesting ideas on what causes its behavior are sure to follow.

    http://www.skyandtelescope.com/astro...e-tabbys-star/

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    Re: Alien megastructure?

    Could It Be: Possible Signs of Extraterrestrial Intelligence?
    By: David Grinspoon | February 29, 2016
    21
    We need to learn how to talk about possible signs of extraterrestrial intelligence.

    Comet Swarm
    This artist’s concept shows a swarm of comets passing before a star.
    NASA / JPL-Caltech
    In my most recent column, I discussed the lack of evidence for technically advanced extraterrestrials. Curiously enough, in the time between writing that and its publication, some possible evidence materialized.

    I’m sure you’ve heard plenty about the star KIC 8462852. The Kepler spacecraft found that its light is quivering in a complex way, like a lantern harassed by a large moth. It doesn’t match anything predicted or observed around any other star. Something huge — perhaps half the star’s diameter — is in orbit there or passing in its vicinity, at times blocking up to 20 percent of the starlight. That’s no planet. The dips in the light have come in an irregular pattern, ruling out a simple orbit and hinting at multiple objects. In the absence of a well-understood, straightforward explanation, it’s reasonable to entertain exotic hypotheses.

    It has long been proposed that technically advanced civilizations should be detectable by their works of “astroengineering.” The quirky character of KIC 8462852 resembles descriptions of “alien megastructures” that one can trace to science fiction going back at least to Olaf Stapledon in the 1930s. In 1960 Freeman Dyson described how advanced societies might surround their stars with enormous solar collectors. Stars hosting such “Dyson spheres” would appear dim in visible light but bright with the infrared glow due to waste heat.

    Whatever the cause of the odd dips in the light from KIC 8462852, it’s clearly not such a Dyson sphere surrounding the whole star. But until scientists have convincingly explained what’s going on, is there anything wrong with entertaining the provocative thought that it could be some kind of huge alien construction?

    How to Discuss Extraterrestrial Intelligence

    Some scientists and pundits want to condemn that idea as ridiculous and unworthy of mention. But it would have been wrong not to consider this enticing possibility for such a strange observation. The correct posture, at this point, is to regard an artificial explanation as extremely unlikely — but not illogical or impossible.

    Perhaps this provides a test case, because we have to learn how to talk about these things. In the decades ahead we will be observing more and more exoplanets with better and better instrumentation (see S&T's October issue for more on that topic). We’ll see some novel things, and when we don’t understand them, then biosignatures and even technosignatures are possible explanations, and we should consider them without going overboard with either skepticism or credulity. We have to be cautious — but if we refuse to consider outlandish and wonderful possibilities, we might miss something truly important.

    The alien hypothesis has increased the interest with which scientists are scrutinizing this star. Out of this will come new knowledge, most likely not about aliens. Promising plans include making new visible, infrared, and ultraviolet observations. The next time the light of KIC 8462852 flickers we can inspect the material properties of the obscuring stuff: Is it dust? A swarm of comets? Or something seemingly artificial? Quite possibly it’s something nobody has thought of yet.

    Perhaps someone will have explained the peculiarities of KIC 8462852’s light curve by the time this column appears in print. On the other hand, the mystery might endure for years, allowing numerous predictions to be made and tested. Imagine all the fiction, fantasy, nonsense, religion, and good science that a possible alien civilization might inspire if generations go by without a definitive answer. It would serve as a fluttering beacon reminding us that we have a lot to learn.

    http://www.skyandtelescope.com/astro...-intelligence/

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    Re: Alien megastructure?

    KIC 8462852 Alien Megastructure Star Updated 01/25/17

    https://www.youtube.com/watch?v=2zfmovRwoC8

    Interesting:

    https://youtu.be/soFrywwneZU

    Theorized that if it was periodic dimming caused by an alien megastructure a dip would occur around Feb 21, 2017 but the first one since 2013 occurred on or around April 24, 2017

    http://www.sciencemag.org/news/2017/...ies-dims-again

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    Re: Alien megastructure?

    More accurate prediction for Tabby's Star says March or late April 2017?

    (excuse the delay, im not used to reddit notifications) The prediction simply comes from the assumption that the two large dips seen in the kepler data are from the same orbiting object (though the dip profiles look nothing alike, it is the best we have to work with). So if dip 1 occurred at Kepler day 792 and the middle of the large complex of dips is day 1540, then the orbital period would be the difference between these: 748 days. Therefore, IF the dips 1 and 2 come from the same orbiting source, then we would expect the 3rd big dip at (1540+748)=2288 days and the 4th to be at (2288+748) = 3036 days. Then add 2454833 to convert "kepler day" to "Barycentric Julian day", we get time for the predicted dip 4 at BJD=2457869. Last step is to use the JD converter to figure out what this means to anyone but a computer . http://aa.usno.navy.mil/data/docs/JulianDate.php We were not monitor the sky when dip#3 would have occurred in April of 2015, but dip 4 is predicted to be at the end of April, 2017. Again, this all lies on the assumption that the large dips we see are from the same object passing in front of us and the star - and this is not necessarily the case. But for now, this is the best guess. ~Tabby

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    Re: Alien megastructure?

    Latest article

    Those ‘Alien Megastructures’ Are Probably Just Dust.

    In 2015, The Atlantic first reported that astronomers had discovered some tantalizing information about a distant star in the Milky Way, located about 1,300 light-years from Earth in a swan-shaped constellation called Cygnus. The star itself, slightly bigger than our sun, seemed pretty ordinary as far as stars in the universe go. But every now and then, the light of the star appeared to dim and brighten.

    This wasn’t the weird part. Astronomers look for faint dips in brightness in their search for exoplanets around other stars all the time. The dimming means that something is passing in front of a star and blocking some light from reaching Earth. Telescope observations have discovered thousands of exoplanets in this way.

    The weird part about this star was the behavior of those light fluctuations. The flickering seemed almost random. Some dips in light lasted a few hours, while others lasted for days or weeks. The light dimmed by 1 percent at some times, a change that would typically suggest the presence of a Jupiter-sized exoplanet around the star. But at other times, the light would dim by more than 20 percent, a drop that suggested something much more massive was passing by.

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    The star’s sporadic dimming stumped astronomers, who dubbed it “the most mysterious star in the universe.” They proposed several natural theories, like a transiting comet. When none seemed to fit the bill, they started considering something else. Could the object passing in front of this star, blocking out the light, be a swarm of alien megastructures built by an advanced civilization?

    It was an exciting explanation, one that hearkened to a kind of technology imagined by the science-fiction writer Olaf Stapledon, and later popularized by the physicist Freeman Dyson, that would allow intelligent extraterrestrial life to harness the energy of their star.

    It’s also probably the wrong one.

    The mysterious flickering around the star in the swan constellation is likely caused by ordinary dust, according to an analysis of new data published Wednesday in The Astrophysical Journal Letters. Astronomers have found that the mystery dimming is much deeper at blue wavelengths than at red wavelengths, which means the object response cosmic dust, which measure less than 1 micron each, smaller than the size of a human red blood cell.ible for it is not opaque. The data suggest that the dimming is likely caused by a cloud of very small particles of cosmic dust, which measure less than 1 micron each, smaller than the size of a human red blood cell.

    “If you imagine you have some light source and a planet—which is an opaque object—goes in front of it, it will block blue light just as much as it would the red light,” said Tabetha Boyajian, an astronomer at Louisiana State University who led the analysis. “What we’re seeing for this star is that the drop in the star’s brightness is much greater in the blue than it is in the red.”

    If the dimming had occurred in all colors equally, megastructures would still be on the table. “The fact that the data came in the other way means that we now have no reason to think alien megastructures have anything to do with the dips of Tabby’s Star," wrote Jason Wright, the Penn State astronomer who first suggested the alien megastructure theory, in a blog post Wednesday. (Astronomers have nicknamed the star Tabby’s Star, after Boyajian.)

    Searches for radio signals coming from the star have also turned up empty, providing another blow to the alien theory.

    The strange flickering from Tabby’s Star was first detected by the Kepler Space Telescope, an exoplanet-hunting mission that started looking for changes in the brightness of stars in 2009. The mission produced an enormous amount of data.

    Boyajian made it public through a program called Planet Hunters and asked volunteers to comb through it, looking for patterns that would be difficult for fast-moving algorithms to spot. In 2011, citizen scientists flagged one star. Of the 150,000 stars Kepler had observed, this was the only one that exhibited this strange behavior.

    After the news of Tabby's Star was made public in 2015, other astronomers started digging into its past. They found another kind of dimming phenomenon, one that spanned years.

    In 2016, astronomers said their examination of old photographic plates from as early as 1890 revealed the star has been gradually decreasing in brightness for more than century. Later that year, astronomers revisited Kepler data and found that the star actually dimmed slightly every year by about .34 percent. Tabby’s Star kept getting weirder and weirder. None of the data fit any one explanation nicely, whether it was a swarm of comets or alien megastructures.

    Cosmic dust started looking like one of the best culprits in October 2017. Astronomers analyzed the light from Tabby's star over time and found more dimming in blue light than in red light—the same effect Boyajian measured during the real-time observations of the dips. Boyajian and other astronomers said Tabby’s Star was probably surrounded by clouds of circumstellar dust, grains that orbit around a star and are slightly bigger than interstellar dust. Circumstellar is just big enough to stick inside the star’s orbit, but too small to block light in all wavelengths.

    The latest analysis comes from data collected between March 2016 and December 2017. Boyajian and her team observed the star with the Las Cumbres Observatory, an effort largely funded by a Kickstarter that raised more than $100,000. In May, the star started to dim. Boyajian tweeted about it, sending astronomers around the world into a frenzy as they raced to point other telescopes at Tabby’s star.

    It was the first time scientists had witnessed one of the star’s mysterious dips in real time. A second dip was recorded in June, a third in August, and a fourth in September. The dimming varied between 1 percent and 2.5 percent, and lasted between several days and several weeks.

    While the latest observations seem to rule out the possibility of alien megastructures, they don’t completely solve the mystery of Tabby’s star. Boyajian and her team had expected to detect an excess of infrared light, created when starlight hits surrounding dust, but they saw none. “That was really surprising,” Boyajian said. “It’s kind of telling us, okay, this is not going to be easy.” There are several possible explanations, including that the dust may be too far from the star to become bright enough to glow in infrared.

    Boyajian said more papers will be coming in the next few months on the rest of last year’s observations. “There’s still a possibility that we don’t really have a theory that’s correct yet,” she said. The cosmic dust theory provides an answer to one of the questions posed by Tabby’s Star, but others remain.

    Their answers may not even be something we would recognize if we saw it. As Wright and his colleague Kimberly Carter wrote in an article last year, “Whatever is responsible may lie outside the realm of known astronomical phenomena.”

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