Abnormally huge transit signal on star KIC 8462852- Alien megastructure?

Abnormally huge transit signal on star KIC 8462852- Alien megastructure?

The telescope Kepler has detected an abnormally huge transit signal blotting out up to 22 percent of the star's light (this star, KIC 84628521500 is 1,500 light years away).
The star KIC 8462852 observed by Keck telescope, at Hawaï. © Keck

In his blog post “Kepler's 'Bizarre' Signal Sparks Alien Intelligence Speculation* (Oct. 16, 2015 on Discovery News), Ian O’Neill discusses the new interpretation of the data—as a huge alien megastructure—proposed by Tabetha Boyajian and Jason Wright.

The only proposed explanation standing on its feet is that of a ‘clump or cloud of comets.’ As says Ian O’Neill, “The comet clump explanation seems to answer many of the mysteries about the strange transit signal.” However, in my opinion, it is lacking in the sense that it doesn’t answer its own mystery: What size would such a ‘cloud of comets’ need to be to occult 22% of a star light?
For example, what percentage of our sun’s light is blotted out by our asteroid belt, and would the observed enigmatic data fit that kind of periodicity? The signal is neither regular nor periodic. The article
states we have only 2 of these transits recorded: A dip of one week in 2011, and “a series of variations over the course of a few months in 2013.” Well, the dynamics looks disordered, more like a swarm of interplanetary spacecrafts moving as a fleet, and why not a load of machines busy around their sun (not specifically one huge big artificial structure like a Dyson sphere). The first step is to analyze the signal to see if it fits either a chaotic natural phenomenon (showing global patterns), or an artificial, civilization-driven, phenomenon—and not to constrain the logic to an ‘either natural OR Dyson-sphere’ question.

(See Wikipedia on Kardashev scale: https://en.wikipedia.org/wiki/Kardashev_scale#Type.C2.A0II_civilization_methods)

 All Type-II civilization methods to draw energy from a star would mean a quasi regular energy output in a period (like the total energy waste of our planet, with its slight oscillations and quasi-regular increase). A Dyson sphere would be absolutely stable and regular, non-periodic. Whatever the method, the amount of captured energy (from whatever source around the civilization-II planet, e.g., the dip in the energy of the star) would be compensated by the increase in energy of the planet plus its waste. Moreover, the process in the short term (e.g. a few years of that planet), would only vary slightly around a mean. 
The plotted data (see figure below) in Ian O’Neill first article** (apart from 3 large dips), show five small dips at irregular intervals, and periods of disturbances (such as between 4 and 5, and a longer one starting at 12, and all the way to the biggest dip between 16 and past 17).

**  Has Kepler Discovered an Alien Megastructure?” (http://news.discovery.com/space/alien-life-exoplanets/has-kepler-discovered-an-alien-megastructure-151014.htm - Oct 14, 2015 )

The transit data for KIC 8462852, featuring the obvious transit features D800 and D1500.
(Extracts of Ian O’ Neill October 16th article:)
“First I really want to emphasize, as I did in my previous blog about KIC 8462852, that the root cause of a very strange Kepler transit signal is most likely due to natural phenomena. (A transit occurs when an exoplanet — or, in this case, something else — drifts in front of its star and Kepler detects a slight dimming of starlight.) After analyzing the unique transit signal identified as being "bizarre" by the Planet Hunters community, researchers did a thorough job identifying a possible mechanism by which significant and distinct dimming events could have been triggered.
“Among the likely natural causes of the star brightness dimming outlined in a paper submitted to the journal Monthly Notices of the Royal Astronomical Society and made available on the arXiv preprint service on Sept. 11, astronomers looked into debris from a possible planetary collision, the presence of circumstellar rings, starspots, and a clump of comets. All possibilities were investigated, but all were unsatisfactory, except for the latter.
“The comet clump explanation seems to answer many of the mysteries about the strange transit signal. A nearby star, only 1,000 AU from KIC 8462852, could have caused some gravitational perturbations during close approach, possibly sending a swarm of comets toward the star, blotting out up to 22 percent of the star's light from Kepler's view.
“The exocomet explanation seems reasonable. Although exocomets have been detected around other stars in the past, this would be the first detection of a vast clump of comets big enough to significantly dim the light of a mature F-type star (around 50 percent larger than our sun). However, an observation of this kind would have to be an incredible stroke of luck; for us to have a NASA space telescope looking in the right place at the right time of this rare collection of comets to pass in front of one star of only 150,000 stars in Kepler's field of view (over a very short time period of 4 years), is crazy lucky. But just because it's a serendipitous observation doesn't mean it's not caused by comets; we were just really, really lucky to see it.
“But then, on Tuesday, an article appeared in The Atlantic; an article that provided a further look into the scientific process of seeking out more extreme possibilities.
“Post-doctorate researcher Tabetha Boyajian, at Yale University and lead author of the original paper, spoke with The Atlantic's Ross Andersen, mentioning that she was currently considering "other scenarios" for the strange transit pattern. And, after sharing the data with Penn State University astronomer Jason Wright, who is planning a follow-up publication, one of those other scenarios came to light: the strange transit signal from KIC 8462852 might be caused by a huge artificial structure.
“Excerpt from The Atlantic article: “Wright and his co-authors say the unusual star's light pattern is consistent with a "swarm of megastructures," perhaps stellar-light collectors, technology designed to catch energy from the star.”
As discussed in Wednesday's Discovery News report, should this signal really be artificial, it could be the first evidence of an advanced alien intelligence that is well on its way to becoming a Type II Kardashev civilization. This is a remote possibility but if all other explanations are exhausted, why not test the alien hypothesis?
Alien Speculation
So, what's next? Unfortunately, with Kepler's primary mission over, we only have 4 years of transit data from KIC 8462852 and only 2 key transit events to study. The first dip in starlight occurred for one week in 2011 and then the second significant event was actually a series of variations over the course of a few months in 2013. That's all we have for now.
The researchers are now hoping to get some observing time on a radio observatory to "eavesdrop" on the star in the hope of carrying out a "directed SETI" campaign, hunting for artificial radio signals emanating from the star system. If they draw a blank on this observing run — and, let's face it, the chances of detecting alien communications are still as slim as ever — it doesn't necessarily mean the "structure" isn't artificial, it could just mean that this hypothetical race isn't communicating via radio waves… or it could mean the alien civilization is no longer there.
Our galaxy, which contains hundreds of billions of stars and countless more planets, is over 13 billion years old. The human race has evolved in the tiniest fraction of this time and modern astronomy has only just opened our eyes to the cosmos over the last couple of hundred years. The likelihood of seeing a thriving civilization of advanced extraterrestrials building some kind of solar array around KIC 8462852 at this precise moment in time is extremely tiny. So it is more likely that if the radio signal hunt turns up empty handed, but the object is proven to be an artificial megastructure, it could be the remnant of a civilization that has come and gone — it could be a huge artifact of a bygone alien age.
The next step is to point a radio antenna at KIC 8462852, just to see whether the system is generating any artificial radio signals that could indicate the presence of something we’d define as “intelligent.” Boyajian and Wright have now teamed up with Andrew Siemion, the Director of the SETI Research Center at the University of California, Berkeley, to get a radio telescope to listen into the star and if they detect an artificial signal, they will request time on the Very Large Array (VLA) to deduce whether any radio signals from that star are the chatter of an alien civilization.

En français: Voir l’article de Chloé Durand-Parenti dans Le Point.fr (16 Oct 2015)
Une civilisation extraterrestre a-t-elle vraiment été découverte ?
Grâce au télescope Kepler, des astronomes ont repéré une étoile au comportement si étrange qu'elle suscite une fascinante théorie. Décryptage.

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