Tabby’s Star is Dipping Again!

In September of 2015, the star KIC 8462852 (aka. Tabby’s Star) captured the world’s attention when it was found to be experiencing a mysterious drop in brightness. In the years since then, multiple studies have been conducted that have tried to offer a natural explanation for this behavior – and even an unnatural one (i.e. the “alien megastructure” theory). At the same time, multiple observatories have been tracking the star regularly for further dimming.

Well, it seems that Tabby’s Star is at it again! On Friday, March 16th, Tabetha Boyajian (the astronomer who was responsible for discovering the star’s variations in flux) and her colleagues reported that the star was dimming yet again. As they indicated recently their blog –  Where’s the Flux? – the star experienced its greatest dip since it was observed by the Kepler mission in 2013.

To recap, in 2015, when Boyajian and her team first reported this strange behavior, Tabby’s Star was observed to be dimming by as much as 22% – at different intervals and for different lengths of time. Since then, explanations for this behavior have ranged from a a circumstellar debris disk, shattered comets or asteroids, the presence of a giant planet, a planet with rings, or even a planet that had been consumed in the past.

However, back in January, Tabetha Boyajian and a team of over 100 astronomers conducted a new study which demonstrated that KIC 8462852 (aka. “Tabby’s Star”) was likely being partially obscured by dust. This study effectively put to rest speculation that the dimming could be caused by an alien megastructure and offered conclusive evidence that the flux was the result of a natural phenomenon.

Nevertheless, on March 19th, Tabetha and her team began reporting how the star’s brightness was once again dropping. Using data obtained by the Las Cumbras Observatory‘s Teide, McDonald and Haleakala Observatories (in Spain, Texas and Hawaii, respectively), they began posting regular updates on its light curve. As they wrote on their blog at the time:

“On Friday (2018 March 16) we noted the last data taken were significantly down compared to normal. Due to poor weather conditions at all 3 sites we weren’t able to observe the star again until last night…  This is the deepest dip we have observed since the Kepler Mission in 2013!  WOW!!”

On March 22nd, the team provided an updated light curve which indicated that the star was rapidly returning to its normal brightness. As they indicated, “The profile of the new dip having a slow decline with a more rapid increase is again reminiscent to that of a backwards-comet.” On March 23rd, observations from the Catalonia Institute for Space Studies‘ (IEEC) Montsec Astronomical Observatory were also included, which indicated the same.

The light curve recorded for Tabby’s Star. Credit: Where’s the Flux?

An update from March 26th indicated that the star’s flux had dropped by a total of 5%, a finding which was confirmed by John  Hall – an observer with the American Association of Variable Star Observers. This constituted the greatest dip since the 22% reported in 2015. As Boyajian declared at the time, “Looks like we beat the record set just last week on the deepest dip observed since Kepler!”

The latest update, from March 27th, indicates that despite bad weather at two of their sites, new data had been obtained which indicated that the star’s flux was going back up again, but was still ~2% below normal. In short, it seems that this latest dimming event – the largest since the team first noticed a change in the star’s flux – has peaked and the star is returning to normal.

While this latest dip in light does not cast the obscuring dust conclusion into doubt, it does show that the mystery of Tabby’s Star may not be completely resolved yet. Based on this and future dimming events, scientists may be forced to refine their theories further. In the end, its all about the process of continuous discovery. And Tabby’s Star is proving to be a very interesting case!

However, one can almost certainly guarantee that fans of the “alien megastructure” theory are going to see this as good news!

Further Reading: Live Science, Where’s the Flux?

You Knew This Day Was Coming. Alien Megastructures Ruled Out for Tabby’s Star. Dust is the Culprit

In September of 2015, KIC 8462852 (aka. Tabby’s Star) captured the world’s attention when it was found to be experiencing a mysterious drop in brightness. In the years since then, multiple studies have been conducted that have tried to offer a natural explanation for this behavior. In lieu of one, there’s been plenty of speculation as to what could be causing the dimming effect – including the controversial “alien megastructure” theory.

Unfortunately, after years of excitement and speculation, the scientific community may have finally driven a nail into this theory’s coffin. According to a new study by a team of over 100 astronomers, and led by Assistant Professor Tabetha Boyajian – who made the original discovery – it now appears likely that KIC 8462852 (aka. “Tabby’s Star”) is being partially obscured by dust and not – I repeat, NOT – an alien megastructure.

The study, titled “The First Post-Kepler Brightness Dips of KIC 8462852“, recently appeared in The Astrophysical Journal Letters. Led by Prof. Boyajian from Louisiana State University in Baton Rouge, the team consisted of astronomers from the Instituto de Astrofísica de Canarias (IAC), the University of La Laguna in Spain, the American Association of Variable Star Observers, and the Center for Exoplanets and Habitability at the University of Warwick.

The study was also made possible thanks to a Kickstarter campaign that Prof. Boyajian and her colleagues launched in 2016. The campaign successfully raised more than $100,000 to pay for observation time so that Boyajian and her colleagues could gather more data on KIC 8462852. In partnership with the Las Cumbres Observatory, they gathered spectroscopic data on the star using a network of telescopes from all over the world.

What they found was that the dimming pattern was most likely caused by a cloud of obscuring dust around the star, as evidenced by the way light coming from the star being unevenly blocked. As Prof. Boyajian explained in a recent LSU press release:

“Dust is most likely the reason why the star’s light appears to dim and brighten. The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”

The theory that KIC 8462852 might be surrounded by an obscuring dust cloud is not entirely new. In fact, a circumstellar debris disk was one of several theories offered in the past two years for the star’s mysterious dimming patterns. Other suggestions included shattered comets or asteroids, the presence of a giant planet, a planet with rings, or even a planet that had been consumed in the past.

LSU Astronomer Tabetha Boyajian (center) and her students and research staff. (Left to right) Robert Parks, undergraduate student Rory Bentley, Assistant Professor Tabetha Boyajian, PhD candidate Tyler Ellis, undergrad Katie Nugent, Professor Geoff Clayton and graduate student Emily Safron. Credit: LSU

However, none of these possibilities were ironclad, and all were based on the first few recorded dips in star’s light curve. In contrast, Prof. Boyajian and her team closely observed KIC 8462852 from the the Las Cumbres Observatory for a fourteen-month period, which ran from March 2016 to December 2017. This allowed them to witness four additional episodes where the star’s light dipped, beginning in May of 2017.

Those who supported the crowdfunding campaign were able to nominate and vote on names for these episodes. The first two dips were named Elsie and Celeste, while the last two were named Skara Brae and Angkor – after ancient lost cities in Scotland and Cambodia. As the team indicated in their study, the first two names held special significance for the team and KIC 8462852 itself:

“The name Elsie is a play on words with ‘L + C,’ short for ‘light curve,’ and is also a wink and a nod to the ‘L’as ‘C’umbres Observatory, for making the project happen. This dip [first] appeared to have a slow decline with a quick rise, which is close to a mirror image of Elsie, which had a quick decline with a slow rise. Elsie (or ‘L C’) in reverse is ‘C L’ or ‘ciel,’ which means ‘sky’ or ‘heavenly’ in French. ‘Celeste’ is the original Latin name from which ‘ciel’ is derived.”

Meanwhile, the dips that bore the name of lost cities were a reference to the activity (also ancient by human standards) astronomers have been observing from this distant star. “They’re ancient; we are watching things that happened more than 1,000 years ago,” the team wrote. “They’re almost certainly caused by something ordinary, at least on a cosmic scale. And yet that makes them more interesting, not less. But most of all, they’re mysterious. What the heck was going on there, all those centuries ago?”

One of the many robotic telescopes part of the Las Cumbres Observatory used to observe Tabby’s Star. Credit: LSU

In addition to providing the first truly solid explanation for Tabby’s Star, this study is also an indication of how the field of astronomical research is changing. Basically, it was conducted by experts in the field who conducted an observation campaign using state-of-the-art instruments. However, it would not have been possible without the engagement and financial support it received from the public.

The original discovery was also possible thanks in large part to citizen scientists and planet hunters, who helped sift through the massive amounts of data obtained by the Kepler mission. As Boyajian herself indicated, the assistance of the public is what made the biggest difference:

“If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked. Again, without the public support for this dedicated observing run, we would not have this large amount of data… It’s exciting. I am so appreciative of all of the people who have contributed to this in the past year – the citizen scientists and professional astronomers. It’s quite humbling to have all of these people contributing in various ways to help figure it out.”

Of course, there is much work to be done and many more questions that need to be answered. But in the meantime, it seems that the single-greatest question about Tabby’s Star – a natural cause or possible evidence of alien activity? – has been tentatively resolved. For those who were hoping that it might be the long-awaited resolution to Fermi’s Paradox I think it’s fair to say we all knew this had to happen sooner or later.

And in the end, is it not better to know that strange and mysterious events have a natural explanation, rather than to not know one way or another? Sure, if you don’t know, it leaves you free to speculate and think what you want, but that’s hardly a scientific attitude. And if we ever want to find evidence of extra-terrestrial intelligence, we need to be able to distinguish natural phenomena from something unnatural.

Remember Carl Sagan’s famous words: “The absence of evidence is not the evidence of absence”? Well, that works both ways! In the meantime, be sure to check out this video of Prof. Boyajian’s TED Talk about the star that bear’s her name:

Further Reading: LSU, The Astrophysical Journal Letters,

Not an Alien Megastructure, a Cloud of Dust on a 700-Day Orbit

The mystery of KIC 8462852 (aka. Boyajian’s Star or Tabby’s Star) continues to excite and intrigue! Ever since it was first seen to be undergoing strange and sudden dips in brightness (back in October of 2015) astronomers have been speculating as to what could be causing this. Since that time, various explanations have been offered, including large asteroids, a large planet, a debris disc or even an alien megastructure.

Many studies have been produced that have sought to assign some other natural explanation to the star’s behavior. The latest comes from an international team of scientists – which included Tabetha Boyajian, the lead author on the original 2016 paper. According to this latest study, which was recently published in The Astrophysical Journal, the star’s long-term dimming patterns are likely the result of an uneven dust cloud moving around the star.

The study, titled “Extinction and the Dimming of KIC 8462852“, was led by Huan Y. A. Meng of the Steward Observatory at the University of Arizona. The team also included members from the Astrolab IRIS in Belgium, the Johns Hopkins University Applied Physics Laboratory (JHUAPL), the University of Cambridge, Iowa State University, Pennsylvania State University, Louisiana State University, and the University of Leuven, Belgium.

Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Credit: NASA/JPL-Caltech

For the sake of their study, the team consulted data that was obtained by NASA’s Spitzer Space Telescope and the Swift Gamma-Ray Burst mission between January and December of 2016. Whereas Spitzer conducted observations in the infrared band, Swift gathered data in the ultraviolet band. This was then compared to visible light gathered during the same period by AstroLAB IRIS’s 68-cm (27-inch) reflecting telescope.

What they found was that KIC 8462852 experienced less dimming in the infrared band than in the ultraviolet. This, they concluded, was a strong indication that material transiting in front of the star was likely no larger than a few micrometers (about one ten-thousands of an inch) in diameter, since anything larger would cause the light to dim equally across all wavelengths.

This finding contradicts many theories that have been ventured since the mysterious dimming of Tabby’s Star was first noticed. As Dr. Meng indicated in a recent NASA press statement:

“This pretty much rules out the alien megastructure theory, as that could not explain the wavelength-dependent dimming. We suspect, instead, there is a cloud of dust orbiting the star with a roughly 700-day orbital period.”

Artist’s concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

Based on the strong dip in the ultraviolet band, the research team also concluded that the particles must be larger than interstellar dust. Otherwise, the pressure caused by KIC 8462852’s solar wind would drive these particles out into space over time. A circumstellar disk of dust particles would not only be able to remain in orbit, it would also explain the uneven changes in the star’s brightness.

So far, this is the best explanation for the mysterious long-term behavior of Tabby’s Star. As with previous observations, much of the credit for this latest study goes to amateur astronomers who assisted in the observations. It was participants in the Planet Hunters project, which provides open to access Kepler mission data, that first noticed that light coming from KIC  8462852 was experiencing strange dips.

In addition, it was the work of amateur astronomers – who provided the necessary technical and software support to AstroLAB – allowed for this study to take place. After the Astrolab group posted the data they had obtained on Tabby’s star in a public astronomy archive, George Rieke (one of the co-authors on this latest study) contacted them and proposed combining their results.

The AstroLAB group consists of Franky Dubois, who operated the telescope during the Tabby’s Star observations, Ludwig Logie, who helps with technical issues on the telescope, and Steve Rau, who processes observations of star brightness, is a trainer at a Belgian railway company. Together, they began monitoring Tabby’s Star after they read Dr. Boyajian 2016 study.

Ever since it was first announced in 2015, there has been speculation as to what could account for the dimming of KIC 8462852. Credit: SentientDevelopments.com

Naturally, more observations and research is needed to confirm this latest study. While it does fit the long-term observations, there is still the matter of shorter-term dimming events. These include the three-day spurts that were noticed in 2017, as well as the major 20-percent dips that were observed during Kepler’s primary mission. The theory that these could have been the result of a swarm of comets is also still a possible explanation.

This theory, which was based on data collected by the Wide-field Infrared Survey Explorer (WISE) mission, could explain both the short period dips and the longer-term dips. Whereas the comets passing in front of the star could explain the former, dust produced by the sublimation of material from the comets as they draw nearer the star (or through collisions) could explain the latter. As Vanaverbeke said:

“Tabby’s Star could have something like a solar activity cycle. This is something that needs further investigation and will continue to interest scientists for many years to come.”

So for those hoping that Tabby’s Star was the first indication of an alien megastructure, there’s still hope (albeit a faint one)! As Professor Loeb of the Harvard Smithsonian Center for Astrophysics (CfA) told Universe Today recently (with regards to a new study he co-authored), there’s always the possibility that dimming patterns are due to massive structures – like a magnetic shield – passing in front of a host star:

“The imprint of a shield built by another civilization could involve the changes it induces in the brightness of the host star due to occultation (similar behavior to Tabby’s star)  if the structure is big enough,” he said. “The situation could be similar to Dyson’s spheres, but instead of harvesting the energy of the star the purpose of the infrastructure is to protect a technological civilization on a planet from the flares of its host star.”

While the Kepler mission is no longer in a position to observe Tabby’s Star (now that it is conducting its K2 mission), next-generation telescopes are expected to pick up where it left off. These include NASA’s James Webb Space Telescope, the Wide Field Infrared Survey Telescope (WFIRST), and ground-based observatories like the Extremely Large Telescope (VLT) array.

Further Reading: NASA, The Astrophysical Journal

Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?

KIC 8462852 (aka. Tabby’s Star) continues to be a source of both fascination and controversy. Ever since it was first seen to be undergoing strange and sudden dips in brightness (in October of 2015) astronomers have been speculating as to what could be causing this. Since that time, various explanations have been offered, including large asteroids, a large planet, a debris disc or even an alien megastructure.

The latest suggestion for a natural explanation comes from the University of Antioquia in Colombia, where a team of researchers have proposed that both the larger and smaller drops in brightness could be the result of a ringed planet similar to Saturn transiting in front of the star. This, they claim, would explain both the sudden drops in brightness and the more subtle dips seen over time.

The study, titled “Anomalous Lightcurves of Young Tilted Exorings“, recently appeared online. Led by Mario Sucerquia, a postdoctoral student at the University of Antioquia’s Department of Astronomy, the team performed numerical simulations and semi-analytical calculations to determine if a the transits of a ringed gas giant could explain the recent observations made of Tabby’s Star.

An artist impression of an exomoon orbiting a ringed exoplanet. Credit: Andy McLatchie

Currently, exoplanet-hunters use a number of methods to detect planetary candidates. One of the most popular is known as the Transit Method, where astronomers measure dips in a star’s brightness caused by a planet passing between it and the observer (i.e. transiting in front of a star). How a gas giant with rings would dim a star’s light was of concern here because it would do so in an irregular way.

Basically, the rings would be the first thing to obscure light coming from the star, but only to a small degree. Once the bulk of the gas giant transited the star, a significant drop would occur followed a second smaller drop as the rings on the other side passed by. But since the rings would be at a different angle every time, the smaller dips would be larger or smaller and the only way to know for sure would be to compare multiple transits.

In the past, researchers from the University of Antioquia developed a novel method for detecting rings around exoplanets (“exorings”). Essentially, they showed how an increase in the depth of a transit signal and the so-called “photo-ring” effect (often mistaken for false-positives in previous surveys) could be interpreted as signs of an exoplanet with a Saturn-like ring structure.

The team that devised this method was led by Jorge I. Zuluaga of the Harvard Smithsonian Center for Astrophysics (CfA), who was also a co-author on this study.  To test this theory with KIC 8462852, the team simulated a light curve from a ringed planet that was about 0.1 AU from the star. What they found was that a tilted ring structure could explain the dimming effects detected from Tabby’s Star in the past.

Artist’s impression of an exoplanet with an extensive ring system. Credit and Copyright: Ron Miller

They also found that a tilted ring structure would undergo short-term changes in shape and orientation as a result of the star’s gravitational tug on them. These would be apparent due to strong variations of transit depth and contact times even between consecutive transits. This too would likely be interpreted as anomalies in signal data, or lead to miscalculations of a planet’s properties (i.e. radius, semi-major axis, stellar density, etc).

This is not the first time that a ringed-structure has been suggested as an explanation for the mystery that is Tabby’s Star. And the team admits that there are other possible explanations, which include the possibility of an exomoon breaking up around a larger planet (i.e. leaving a debris disk). But as Sucerquia indicated in an interview with New Scientist, this latest study does offer some compelling food for thought:

“The point of this work is to show the community that there are mechanisms that can alter the light curves. These changes can be generated by the dynamics of the moons or the rings, and the changes in these systems can occur in such short scales as to be detected in just a few years.”

Another interesting takeaway from the research study is the fact that oscillating ring structures could also account for the strangeness of some light-curves that are already known. In other words, its possible that astronomers have already found evidence of ringed exoplanets, and simply didn’t know it. Looking ahead, it is possible that future surveys could turn up plenty more of these worlds as well.

Of course, if this study should prove to be correct, it means that what some consider our best hope of finding an alien megastructure has now been lost. Admittedly, this would be a disappointment. If there’s one thing about the mystery of Tabby’s Star that has been consistently intriguing, it’s the fact that a megastructure couldn’t be ruled out. If we have come to that point at last, there’s not much more to say.

Except, perhaps, that’s it’s a big Universe! There’s sure to be a Kardashev Type II civilization out there somewhere!

Further Reading: New Scientists, arXiv

New Ideas for the Mysterious Tabby’s Star: a Gigantic Planet or a Planet With Rings

KIC 8462852 (aka. Tabby’s Star) captured the world’s attention back in September of 2015 when it was found to be experiencing a mysterious drop in brightness. A week ago (on May 18th), it was announced that the star was at it again, which prompted observatories from all around the world to train their telescopes on the star so they could observe the dimming as it happened.

And just like before, this mysterious behavior has fueled speculation as to what could be causing it. Previously, ideas ranged from transiting comets and a consumed planet to alien megastructures. But with the latest studies to be produced on the subject, the light curve of the star has been respectively attributed to the presence of a debris disk and Trojan asteroids in the system and a ring system in the outer Solar System.

The first study, titled “KIC 8462852: Will the Trojans return in 2021?“, was written by a team from the University of Valencia, the Institute of Physics of Cantabria (IFCA) and the Astrophysical Institute of Andalusia (IAA). The paper was recently submitted to the Monthly Notices of the Royal Astronomical Society, and presents the argument that the dimming of Tabby’s Star can be explained by the presence of stable debris.

Diagram of the KIC 8462852 system, showing the possible influence of Trojans on its brightness. Credit: F. Ballesteros et al.

Led by Fernando J. Ballesteros, the team used data obtained by the Kepler mission to create a model of the system that could account for all the dips in brightness. These include the up to 20% drop that was observed in 2015 and the non-periodic repetitions and asymmetric dips that followed. From this, they determined that a ringed body and Trojan asteroids that share its orbit could explain the first large dip and the subsequent period of dips.

This explanation not only offers an entirely natural account of what could be causing the star to dim, but also offers a prediction that (if true) would confirm their theory. As they state in their paper:

“Whereas most of the scenarios that have already been discussed by other authors invoke the presence of astronomical objects that have never been directly observed, from the comet clouds in Boyajian et al. (2016) to the Dyson sphere in Wright et al. (2016), our model requires the presence of relatively familiar objects, namely a large planet with orbiting rings and a cloud of Trojan asteroids. Moreover, our model allows us to make a definite prediction: the leading Trojan cloud should induce a new period of irregularities in the light curve approximately in 2021.”

Interestingly, Jason Wright – an associate professor from Penn State University and the one who proposed the alien megastructure theory – chimed in on this paper. And it only seems fair, since the team refer to his work in their study! As he indicated on his website, AstroWright, the theory does have several strong points, but does not account for certain observations.

Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Credit: NASA/JPL-Caltech

As he states, the dips observed from Tabby’s Star are quite steep, which is something natural phenomena cannot easily account for. Their study also does not address things like secular dimming, or the upper limits of IR and millimeter wave-observations. But perhaps most glaring, according to Wright, is the mass that would be required to create the kind of dimming that has been seen:

“They need a lot of asteroids: they don’t actually say how much, but the number they do give is huge: over a Jupiter mass of them!  It’s not clear to me how stable such a swarm could be co-orbital to an actual planet.  Part of the reason Jupiter’s Trojan asteroids work as they do is that they don’t really perturb Jupiter. Also, how do you keep a Jupiter mass of material from collapsing or falling into the planet?  Also, where would you get a Jupiter mass of rock?!”

The second paper, titled “Tabetha’s Rings”, was also recently submitted to MNRAS. Written by Professor Jonathon Katz of the Department of Physics and McDonnell Center for the Space Sciences at Washington University, the paper argues that the dips observed from Tabby’s Star could be caused by matter in the Solar System – specifically, a ringed object that lies between Kepler’s line of sight and KIC 8462852.

Based on the interval between dips, and the orbit and line of sight of the Kepler mission, Katz calculated what the distance of this possible ring would be, and provides estimates on the size and distribution of particulate matter within it as well. As he wrote in his study, a 600 m large object would be able to obscure all light coming from the Tabby’s Star, although only briefly.

Could a ring-like structure in the outer Solar System be what’s causing the observed dimming of Tabby’s Star? Credits: NASA/JHUAPL/SwRI

What’s more, given the orbital motion of Kepler (and the Earth), the observed dips in brightness would require the existence of an obscuring cloud that extends along the ring a distance equal to the distance the telescope travels. Ultimately, this paper is more of a thought experiment than a definitive hypothesis, one which Katz acknowledges in his conclusions.

“The occurrence of deep dips in two epochs separated by about two Kepler-years is a hint that the phenomenon may be local rather than circumstellar,” he states. “This evidence is suggestive but not statistically compelling because the interval differs from an exact integer multiple of Kepler-years by a few percent. However, the difficulty of developing a compelling circumstellar model and the history of discovery of narrow planetary rings by stellar occultation justify investigation of possible explanations involving Solar System rings.”

Another interesting aspect of Katz’s study is the fact that it too makes predictions about future dimming events. In short, his hypothesis indicates that future dips may be observed from Earth at intervals that are just a year apart. But according to Wright, who commented on this paper as well, this seems like a miscalculation.

“Some of the implications are worked out, but some of the math seems wrong to me (he predicts that the dips will be visible every 365.25 days from earth, which ignores the orbital motion of that object),” he wrote. However, Wright also congratulates Katz for making this argument since it is similar to one he himself made a year ago (which Katz acknowledged in his paper).

Dyson Sphere by Eburacum45
Could this be what’s causing Tabby’s Star to experience drops in brightness, an alien megastructure? Credit: Eburacum45

Last summer (August 31st, 2016), when writing on the subject of what could be causing Tabby’s Stars observed dips in brightness, Wright considered the possibility that a Solar System Cloud might be responsible:

“If there is something between us and the star, then proper motion should change our line of sight through it… For the moment, let’s put the hypothetical cloud out at 10,000 AU. Parallax would make it appear to move by about 20 arcseconds, and its orbital motion would move it by about the same amount over 100 years. So if the cloud is 20″ across, it could be responsible for the long-term dimming.  This would also help explain the 1.96 Kepler year gap between the two dips (although not the lack of dips at 0.98 years): that’s the time it takes our line of sight from Kepler to return to about the same place, with ~1% taken off due to the cloud’s own orbital motion.”

However, Wright also pointed out the flaws in this theory, stating that such a ring could not account for all the observations made of Tabby’s Star, and that he and other astronomers were at a loss to explain how such a ring could have been caused. “Not only is Boyajian’s Star way above the ecliptic (but does that even matter at 10,000 AU?), but a 20″ cloud at 10,000 AU would be 1 AU across.  What could cause it?” he wrote.

In the end, we may never know what is behind KIC 8462852’s strange behavior. But our ongoing efforts to gather additional information are making increasingly educated guesses possible. As we eliminate more and more in the way of possibilities, we are getting closer to an explanation that actually fits.

Next generation telescopes will certainly help in this regard. And who knows? Someday we may actually be able to explore this system directly and see if any our theories were correct!

Further Reading: AstroWright, MNRAS, (2)

The Star That Probably Doesn’t Have an Alien Megastructure (But Maybe it Does) is Dimming Again

In September of 2015, scientists announced that the star known as KIC 8462852 (aka. “Tabby’s Star” or “Boyajian’s Star”) was experiencing a strange dip in luminosity. At the time, astronomers indicated that this mysterious behavior could be the result of comets transiting in front of the star, but other (perhaps more hopeful) individuals claimed that it could also be the result of an alien megastructure.

This led to a flurry of studies and articles that sought to offer entirely natural explanations for what has been observed. Even SETI weighed in, indicating that they would begin searching for indications of radio signals coming this mysterious star. But after two years and multiple studies that offer explanations other an alien Dyson Sphere (or some other type of megastructure), the star is at it again!

The first indications that the star was dimming again were reported late last month by the Fairborn Observatory in Arizona. The robotic telescope spotted what might be a dip in brightness on April 24th, 2017. Within a week, the brightness returned to normal levels, but the event (known as “Event 1” in the star’s light curve, shown below) caught the interest of astronomers around the world.

Preliminary analysis of incoming data of KIC 8462852, showing the apparent dip. Credit: Matthew Muterspaugh/Tennessee State University/CEISEM

Then on May 18th, a more significant drop began, which prompted the observatory’s scientists to put out the call to observatories around the world to begin turning their telescopes to Tabby’s Star. According to the alert issued by the Observatory, the star had already dimmed by 2% after just one night of observation. As soon as the Sun set in their respective regions, observatories around the world began monitoring the star and recording its light curve.

This included the Center of Excellence for Information Systems Engineering and Management (a research laboratory at the University of Tennessee), the W.M. Keck Observatory in Manau Kea, the American Association of Variable Star Observers (AAVSO), and the MMT Observatory in Arizona (which has been providing additional spectroscopy).

The Las Cumbres Observatory Global Telescope Network (LCOGT), which was regularly monitoring the star already, also joined the observation party. While this was happening, Tabetha Boyajian (for whom the star is named) called Jason Wright – an associate professor of astronomy at Pennsylvania State University – to tell him the news. Wright received the call on Friday, May 19th, at 4 a.m., at which point, he was told that the dimming had reached 3%.

Wright then tweeted the news out 24 minutes later (4:24 a.m. EDT) to let the world know that the most mysterious star in the known Universe was acting up again! Hours later, Wright and SETI Director Andrew Siemion also held a live webcast to update the public on everything that was being learned and to explain precisely what the scientific community was looking for.

As Wright said during the course of the webcast, which began at 2 p.m. EDT (11 a.m. PDT), the goal here is to obtain a “spectral fingerprint” from the star:

“Tabby’s star… went through a lot of very strange dimming events that got up to 22% dimmer during the Kepler Mission, and since then we’ve been eagerly awaiting another dip. And the reason that we’ve been waiting for that is that whatever is causing the star to get dimmer will leave a spectral fingerprint behind. So if it’s a lot of dust between us and the star that’s passing by, it should block more blue light than red light. If there’s gas in that dust, that gas should absorb very specific wavelengths. So we’ve been eager to see one of these changes, these dips in the star, so we can take the spectra.

In other words, if we’re dealing with entirely natural phenomena – like clouds of debris, comets, a consumed planet or anything other than an alien megastructure – that will become clear from the spectra we obtain from the star. If, however, the spectra does not conform to these parameters, we will once again be back to speculating about the possible cause. And you can bet your bottom dollar the alien megastructure crowd will be out in full force!

As Wright went on to explain, during the preceding week, there were indications that something was happening around the star. However, none of it was significant enough for observatories to go from “yellow alert” – i.e. in a heightened state of readiness – to actively training their telescopes on the star. The reason for this is that telescopes have their observation time scheduled weeks or even months in advance.

Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Credit: NASA/JPL-Caltech

As such, no one can hit the override button and demand that their telescopes be trained on a new target without having a very good reason. However, on Thursday, the staff at Pennsylvania State University were waiting for data that would indicate if the dip was really happening. By Friday, in the early morning hours, that is precisely what they got! As Wright recounted during the broadcast:

“[At] about 4 a.m. this morning I got a phone call from [Tabitha Boyajian] that Fairborn Observatory in Arizona had confirmed that the star was 3 percent dimmer than it normally is. That is enough that we are absolutely confident that this is no statistical fluke. We’ve now got it confirmed at multiple observatories, I think.”

So far, several observatories have provided spectra that indicates that the star really is in the process of dimming. And in the coming days and weeks, additional observatories are expected to join in. This may include the Green Bank Observatory, which will collect radio observations, and even space-based observatories like the Swift Space Telescope – which will provide both optical and ultraviolet data.

Regardless of what they find, you can expect we will be hearing about shortly thereafter! And in the meantime, be sure to check out the full live broadcast below:

Further Reading: Sky & Telescope

Weekly Space Hangout – January 27, 2017: Kimberly Cartier & Exoplanet WASP 103b

Host: Fraser Cain (@fcain)

Special Guest: Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )

Kimberly Cartier is a PhD candidate in the Department of Astronomy & Astrophysics at the Pennsylvania State University where her primary research interest is extra-solar planets. Kimberly focuses on communication, public speaking, teaching, and public outreach, and is a regular contributor to the Weekly Space Hangout.

Kimberly is the lead author on a recent paper in which the atmospheric characteristics of exoplanet WASP 103b are analysed. (https://arxiv.org/pdf/1611.09272v1.pdf) Please join us today as Kimberly discusses their findings.

Guests:
Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)
Paul M. Sutter (pmsutter.com / @PaulMattSutter)

Their stories this week:
Using AI to study supernovae

We finally made metallic hydrogen!

Quality control problems with Russian rockets

A new test for life on other planets

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page

Finally, An Explanation for the Alien Megastructure?

Back in October of 2015, astronomers shook the world when they reported how the Kepler mission had noticed a strange and sudden drop in brightness coming from KIC 8462852 (aka. Tabby’s Star). This was followed by additional studies that showed how the star appeared to be consistently dimming over time. All of this led to a flurry of speculation, with possibilities ranging from large asteroids and a debris disc to an alien megastructure.

But in what may be the greatest explanation yet, a team of researchers from Columbia University and the University of California, Berkley, have suggested that the star’s strange flickering could be the result of a planet it consumed at some point in the past. This would have resulted in a big outburst of brightness from which the star is now recovering; and the remains of this planet could be transiting in front of the star, thus causing periodic drops.

For the sake of their study – titled “Secular dimming of KIC 8462852 following its consumption of a planet“, which is scheduled to appear in the Monthly Notices of the Royal Astronomical Society – the team took the initial Kepler findings, which showed sudden drops of 15% and 22% in brightness. They then considered subsequent studies that took a look at the long-term behavior of Tabby’s Star (both of which were published in 2016).

Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Could these be responsible for its peculiar dips in brightness or is there a biological reason?  A small red dwarf star (above, left) lies near Tabby’s. Credit: NASA/JPL-Caltech

The first study, conducted by Bradley Schaefer of Louisiana State University, showed a decrease of 14% between the years of 1890 and 1989. The second study, conducted by Ben Monet and Joshua Simon (of Caltech and the Carnegie Institution of Washington, respectively), showed how the star faded by 3% over the course of the four years that Kepler continuously viewed it.

They then attempted to explain this behavior using the Kozai Mechanism (aka. Kozai Effect, Lidov-Kozai mechanism), which is a long-standing method in astronomy for calculating the orbits of planets based on their eccentricity and inclination. Applied to KIC 8462852, they determined that the star likely consumed a planet (or planets) in the past, likely around 10,000 years ago.

This process would have caused a temporary brightening from which the star is now returning to normal (thus explaining the long term trend). They further determined that the periodic drops in brightness could be caused by the remnants of this planet passing in high-eccentricity orbits in front of the star, thus accounting for the sudden changes.

Their calculations also put mass constraints on the planet (or planets) consumed. By their estimates, it was either a single Jupiter-sized planet, or a large number of smaller objects – such as moon-mass bodies that were about 1 km in diameter. This latter possibility seems more inviting, since a large number of objects would have produced a field of debris that would be more consistent with the dimming rate observed by previous studies.

Artist’s concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

These results are not only the best explanation of this star’s strange behavior, they could have serious implications for the study of stellar evolution – in which stars gobble up some of their planets over time. As Brian D. Metzger, an assistant professor from the Columbia Astrophysics Laboratory and the lead author on the paper, explained in an interview with New Scientist:

“We estimated that if Tabby’s star were representative, something like 10 Jupiters would have to fall into a typical star over its lifetime, or maybe even more… These transits only last a few days, so when we see one, we have to alert all the telescopes and basically point every telescope we have at Tabby’s star.”

No doubt, the mystery of Tabby’s star will endure for some time to come. We can only hope that with ongoing observation, we might sort out exactly what is taking place in this far-flung system. But for the time being, the possibility that what are we seeing is the star returning to its normal state, and being occasionally dimmed by transiting pieces of debris, is the most plausible explanation yet.

Suffice it to say, the alien megastructure enthusiasts will likely be taking this latest study with a grain of salt! You have to admit, a megastructures is a VERY enticing possibility!

Further Reading: ArXiv

Weekly Space Hangout – November 18, 2016: Dr. Jason Wright and Tabby’s Star

Host: Fraser Cain (@fcain)

Special Guest:
Dr. Jason Wright is Professor in Penn State University’s Department of Astronomy and Astrophysics. Jason studies nearby stars, their ages and activity levels, and their planetary systems (exoplanets.) Jason also does a lot of outreach and research about Tabby’s Star (the “”alien magastructure”” star.)

Guests:

Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )
Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)

Their stories this week:

The tilting of Pluto

GOES-R weather satellite

More about Saturn’s hexagon

High-energy electron shenanigans around Earth

Close-ups of Ceres’ bright spot

Great Valley found on a shrinking Mercury

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page.

The Search Is On For Alien Signals Around Tabby’s Star


There’s a remote chance that inexplicable light variations in a star in the Northern Cross may be caused by the works of an alien civilization.

1,480 light years from Earth twinkles one of the greatest mysteries of recent times.  There in the constellation Cygnus the Swan, you’ll find a dim, ordinary-looking point of light with an innocent sounding name — Tabby’s Star.  Named for Louisiana State University astronomer  Tabetha Boyajian, who was the lead author on a paper about its behavior, this star has so confounded astronomers with its unpredictable ups and downs in its brightness, they’ve gone to war on the object, drilling down on it with everything from the Hubble to the monster 393.7-inch (10-meter) Keck Telescope in Hawaii.

Tabby’s Star was uncovered by the Kepler Space Telescope during its examination of of more than 150,000 stars in the Milky Way. Kepler sought out stars accompanied by planets. By recording tiny, repeating fading of the star’s light as a planet passes in front a star, astronomers could determine the planet’s size, orbit and much more. All told, Kepler nabbed more than 2,300 new planets orbiting a host of stars in the constellations Lyra and Cygnus.

This graph shows the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude up to 22%. The usual drop in light when an exoplanet transits its host star is a fraction of a percent. The star’s normal brightness has been set to “1.00” as a baseline. Credit: Boyajian et. all
This graph shows the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude up to 22%. The usual drop in light when an exoplanet transits its host star is a fraction of a percent. The star’s normal brightness has been set to “1.00” as a baseline. Credit: Boyajian et. all

Among the stars Kepler viewed in its survey was one KIC 8462852 (Tabby’s Star). Unlike the others, its light dimmed in a completely unpredictable way. Things in orbit produce repeatable patterns, so astronomers began searching for alternative explanations. Might the star be variable? Lots of stars undergo physical changes such as pulsations or even explosions that cause them to vary in brightness. Nope. Based on its type, a stable star similar to the sun, and the fact that most of the time, it remains shining with a steady light, it didn’t fit the pattern.

Tabby's Star shines at magnitude +11.7 in the constellation Cygnus the Swan (Northern Cross) high in the southwestern sky at nightfall in late October. A 6-inch or larger telescope will easily show it. Source: Stellarium
Tabby’s Star shines at magnitude +11.7 in the constellation Cygnus the Swan (Northern Cross) high in the southwestern sky at nightfall in late October. A 6-inch or larger telescope will easily show it. Source: Stellarium

The star dims by as much as 22% for days at a time at irregular intervals. Stars fade and re-brighten, but not in the way this star does according to astronomers. Researchers ruled out many possibilities including instrumental errors, starspots (like sunspots but on other stars), dust rings seen around young, evolving stars (this is an older star) and pulsations that can cloak it with light-absorbing dust clouds. Dust clouds don’t work because they’d warm up in the star’s light and radiate heat that we could detect with infrared telescopes. We see no excess of glowing dust, ruling that possibility out, too.

Casting about for potential answers, Boyajian and team hit on the hypothesis that an enormous cloud of comets might be behind the light fluctuations. Imagine these comets, fragile creatures that they are, breaking up into fragments that cascade into smaller pieces over time, creating a host of irregular and chaotic variations in Tabby’s light.

Artist's impression of an orbiting swarm of dusty comet fragments around Tabby's Star. Could these be responsible for its peculiar dips in brightness or is there a biological reason?  A small red dwarf star (above, left) lies near Tabby's. Credit: NASA/JPL-Caltech
Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Could these be responsible for its peculiar dips in brightness or is there a biological reason?  A small red dwarf star (above, left) lies near Tabby’s. Credit: NASA/JPL-Caltech

While that may be a reach, there’s even a stranger possibility.  Jason Wright, an assistant professor of astronomy at Penn State, would like us to consider an alien civilization as the cause. Although the possibility is a remote one, he asks us to consider that an alien civilization may be building a megastructure known as a Dyson Sphere around its home star. A Dyson Sphere is a hypothetical sphere constructed around a star. Built of enormous solar panels, it would capture the star’s energy and convert it into electricity to power a technological civilization.

Now imagine if you will, thousands of huge panels in various stages of construction and position orbiting Tabby’s Star, and you just might have an explanation for its mysterious ups and downs. Far-fetched? Of course. But there may be a way to prove it.

The Green Bank Telescope is the world’s largest, fully-steerable telescope. The GBT’s dish is 100-meters by 110-meters in size, covering 2.3 acres of space. The telescope is currently being used in a new SETI (Search for Extraterrestrial Intelligence) attempt to look for possible alien radio signals from Tabby's Star. Credit: NRAO/AUI/NSF
The Green Bank Telescope is the world’s largest, fully-steerable telescope. The GBT’s dish is 100-meters by 110-meters in size, covering 2.3 acres of space. The telescope is currently being used in a new SETI (Search for Extraterrestrial Intelligence) attempt to look for possible alien radio signals from Tabby’s Star. Credit: NRAO/AUI/NSF

A technologically advanced civilization would presumably need to communicate over long distances just like humans do. We use radio and TV, both of which transmit at very specific and narrow frequencies. Every time you go up and down the radio dial, each station you hear is beaming powerful radio waves at a specific frequency or vibration rate. Natural processes are more casual with a broader spread of frequencies. If we could detect a powerful signal at a specific frequency coming from Tabby’s Star, it could potentially be an indication of an alien species at work transmitting their own version of Dancing with the Stars.

One possibility for the weird light variations from Tabby's Star might be a Dyson Sphere built by an alien civilization around the star to harness its power. Credit: UC Berkeley
One possibility for the weird light variations from Tabby’s Star might be a Dyson Sphere built by an alien civilization around the star to harness its power. Credit: UC Berkeley

So how do we do this? How can even know what frequencies they’ll be using to transmit? Well, you take the Green Bank Radio Telescope, the largest fully steerable radio telescope on the planet, and hook it up with a new SETI instrument that can look at an enormous swath of bandwidth simultaneously in billions of different radio channels. That’s exactly what happened Wednesday night (Oct. 26) as part of the Breakthrough Listen project, a $100 million initiative by Russian tycoon Yuri Milner to search for intelligent life in the universe.  

University of California Berkeley astronomers devoted eight hours of scope time last night “listening” to Tabby’s Star for potential signs of an extraterrestrial civilization. They’ll spend two more nights in the coming two months at it and then analyze the data, a process that will take more than a month. Perhaps then we’ll finally get an answer. I hope it’s an alien one, but of course that’s a long shot. Stay tuned.

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