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I was wondering about the light dimming of the 'alien megastructure' star. From what I understand, for it to be a planetary body, it would have to be some 20 times the size of Jupiter. Is it possible that it could be caused by some huge, dense gas cloud, orbiting around the star?
The light curves don't look at all like anything transiting. The ingress and egress profiles and the timing are way beyond that kind of explanation. Not planets, not comets, not clouds, not alien super structures.
No infrared light from dust or gas has been detected, as they should've been if the starlight had heated small particles. And since this is an F star with about 50% larger diameter than the Sun, which contains 99% of the mass in our Solar System, you can imagine how huge any comet/dust/gas cloud has to be to cover 22% of it.
No brightening of the starlight has been detected, as this allegedly huge"cloud" orbits behind the star and should reflect light to us. Shouldn't those huge icy comet clouds reflect some starlight?
Jupiter is about as large as a planet can get, even with 10+ times more mass, its volume would not increase by much. Gas giants differ much more in mass than in volume. An object 20 or 200 times more massive than Jupiter would be a roughly Jupiter sized red dwarf star, and that is not what has been observed at "Tabby's star".
The anomalies correlate strictly with the telescope's orbital period and orientation and are obviously a man made artefact because of some unforeseen malfunction of the instrument, nothing astrophysical is involved.
There are some theories to explain that. The following explanations, I took from wikipeda's article.
The star has a small companion red dwarf which just crossed its Oort cloud equivalent (at 885 UA). A passing star this close would surely cause havoc and serious disturbances to comets' orbits. This could result in a swarm of comets being thrown into the inner stellar system at once in highly excentric orbits. However, there are severe doubts about this.
It was also proposed that a planet with a very big ring system transits the star (or perhaps, nearly misses and just part of the rings transit the star). This is not unprecedent, and was already seen with another star.
Astronomer Jason Wright suggested that the star might be younger than it seems and it is still coalescing material around it.
Astronomer Bradley Schaefer presented just a few days ago (2016-01-13) a study where he concludes that the star dimmed roughly 20% from 1890 to 1989, and that this is unprecedent for a F-type star. So, there could be still more weird things going on than previously thought.
NASA Infrared Telescope Facility found similiarities with another star, Eta Corvi, which is undergoing a Late Heavy Bombardment.
Wikipedia's article also cites another possibility (which took some headlines around the world). But this is just some (unfortunately notable) sensacionalistic (un|pseudo)jornalistic claim that nobody can take seriously:
- There is an advanced alien civilization building a giant device like a Dyson Sphere or something similarly big.
LocalFluff posted an answer suggesting another possibility:
The anomalies correlate strictly with the telescope's orbital period and orientation and are obviously a man made artefact because of some unforeseen malfunction of the instrument, nothing astrophysical is involved.
So, the conclusion (at least my conclusion) is that we simply don't know yet what is happening and we need many follow up observations which will likely tell us a lot. Specially somewhere around May of 2017, when it is predicted that the strange megastructure transit should happen again.
I personally would guess that the close encounter with the red dwarf triggered a Late Heavy Bombardment. But this is only a guess from mine and I have no way to provide evidence for it.
I've been pondering the dimming of this star for a couple months now and have come up with a plausible explanation. The dimming is probably caused by a very dim companion dwarf star in a highly elliptical orbit where its closest approach to KIC8462852 (Tabby's Star) is on, or near, the same path as our line of sight. The gravitational pull from the dwarf would create tidal forces on Tabby's star causing it to bulge in the same way our moon causes the oceans to bulge.
As is commonly known, stars that spin very fast tend to bulge at their equators due to centripetal force and this results in decreased pressure within the star… this decreased pressure slows down the nuclear fusion causing a dimming effect at the equator. Consequently, as the bulging equator causes the north and south poles to get closer together, they get brighter due to the increased pressure because they are closer to the stars core. So with Tabby's star, as the dim dwarf is at its closest approach, it causes Tabby's star to bulge a bit… that bulging causes nuclear fusion to slow, causing a dimming affect… combine this with the dwarf star blocking some of the light itself and I think we could account for the 20% reduction. The next mystery that has to be explained is the 100 year dimming of the star… I believe that as the two companions interact with each other, material from each is probably ejected and probably stays within a close orbit of the main star. This would account for a pattern of continuous dimming as this material built up on each pass. This would also account for why we don't see any infrared signature because the ejected materials orbit is too close to distinguish it from the main star.
If I'm right, our telescopes should be able to see the main star wobble back and forth (alot) as the dwarf rapidly transits from its approach on one side of the star, then to the other side on during its departure.
‘Alien megastructure’ could explain mysterious new Kepler results
There’s a new mystery in the universe and it goes by the name KIC 8462852. It is a star approximately 1500 light years away from the Earth, and displays a strange pattern of dimming that has astronomers scratching their heads.
With many natural causes apparently ruled out, there is even the suggestion that the signals could be caused by a giant structure, built in space near the star, presumably by extraterrestrials.
The unexplained signals have been found in data collected by Nasa’s Kepler Space Telescope. The mission was launched in 2009 and was designed to find planets by looking for the small dip in light caused when a planet passes in front of the star and blocks a small portion of the light.
It has been remarkably successful adding thousands of planets to the known roster. But in all the 150,000 stars that Kepler has monitored, none have ever looked like KIC 8462852. It stands out because the star dims so dramatically.
Whereas a planet will drop the light by a percent or two at most, this star dims by up to 20 percent. Also unlike a planet, which orbits the star and causes the drop to repeat, these dimmings took place at random intervals during the 1600 days that Kepler was monitoring the star.
Around the 800-day mark, the star’s light dropped by 15 percent, Then around the 1500-day mark, there was a flurry of dimming with one dropping 20 percent of the starlight. To fall that much, the object passing in front of the star must be almost half the diameter of the star. Yet Jupiter, the largest planet in our solar system, is only one-tenth the diameter of the Sun.
To rub salt into the wound, KIC 8462852, is estimated to be about 1.5 times larger than the sun, making the necessary object vast indeed. So it cannot be a planet.
Tabetha Boyajian, Yale University, led the investigations into the mysterious signals and found that the most likely natural cause was the break-up of a comet around the star. As the icy remains expand into giant clouds they could temporarily block out the light, causing the observed signal. But this should cause dust to scatter around the star, producing an excess of infra-red radiation that should be easily detected from Earth. As yet, no such signal has been found.
According to the The Atlantic, Boyajian said that there were “other scenarios” that she was considering. And these are where the aliens come in.
Jason Wright, an astronomer from Penn State University, has been investigating what a huge alien construction in space might look like from Earth. He told The Atlantic: “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.”
It would have to be a huge space station indeed to block out that amount of light, hence the epithet “alien megastructure” that is currently setting Google alight.
This is not the first time that astronomers have speculated about aliens when confronted with an unexplained phenomenon. Famously, the discovery of rotating stellar corpses, eventually called as pulsars, were first suggested to be aliens. The researchers even cheekily labelled the reading ‘LGM-1’ for “little green men”.
When hugely powerful gamma-ray bursts (GRBs) continued to defy explanation decades after their discovery, some suggested they could be the optical equivalent of a sonic boom, taking place because alien starships were accelerating to warp speed. The GRBs were eventually discovered to be exploding stars.
A natural explanation is almost certainly the case here too.
Many of the same objections to natural causes apply to the alien megastructure hypothesis too. Namely, the structure should be in orbit around the star and so should lead to periodic dips in the light.
Also, if something is absorbing 20 percent of a star’s light, it is going to get hot and that means it is going to re-radiate that energy at infrared wavelengths but, as mentioned, no IR-excess has been detected.
The only way to clear up this mystery is to make more observations. Boyajian suggests long-term monitoring from ground-based telescopes to look for a recurrence of the dimming events, and is working with Wright to use a radio telescope to listen in for alien broadcasts leaking from the system.
That ‘alien megastructure’ star might actually be a planet-eater
Tabby’s Star probably isn’t surrounded by an energy-sucking alien super-structure. But it may have eaten a nearby planet.
The star, known more formally as KIC 8462852, has baffled scientists by quickly and erratically losing brightness. In observations made over a period of just 100 days, the Kepler telescope captured the star dimming dozens of times, and once dramatically so—by 22 percent.
That’s not just mysterious—it’s nearly unexplainable.
Having ruled out other, less enthralling explanations, like interstellar dust, some astronomers suggested that advanced alien life might be responsible for altering the star’s luminosity. In theory, a civilization profoundly more advanced than ours could have built a Dyson Sphere around KIC 8462852, a concept developed by physicist Freeman Dyson in the 1960’s. Such a super-structure could (hypothetically) surround a star and collect the totality of its massive energy output. That could charge a lot of electric cars. . . or spaceships.
A new study set to be published Monday in the Monthly Notices of the Royal Astronomical Society suggests that smart aliens aren’t responsible for KIC 8462852’s dimming. Instead, the authors suggest, a planetary collision with Tabby’s Star is to blame. This crash would explain not only why Tabby’s Star has had wild fluctuations in brightness as of late, but why the star has been dimming gradually over the course of the last century.
It seems strange that a spectacular collision between a star and planet would cause a star to become dimmer, explains Ken Shen, a UC Berkeley astronomer and author on the study. But, says Shen, “the star has to eventually go back to being dimmer—the equilibrium state—the state that it was at before the collision.”
KC 8462852’s more recent and erratic dimming episodes, however, can be explained by a mess of debris moving around the star and absorbing its light, sometimes making it appear significantly dimmer to us Earthlings.
One possibility is that a rocky, Earth-like planet was pushed into Tabby’s Star. As it got closer, explains Brian Metzger, a Columbia University astrophysicist and one of the study’s authors, the star could tear off the planet’s mantle, leaving a hot, chaotic bunch of material—perhaps the mass of the moon—off-gassing around Tabby’s Star. The ensuing clouds of gas and dust could absorb Tabby’s light. Meanwhile, the star would consume the planet’s core.
Or, says Metzger, a massive Jupiter-sized planet could have been pushed into Tabby’s Star, leaving some of its moons to be stripped apart by Tabby’s gravity and leaving a wealth of cosmic wreckage in orbit around the star.
But what might have pushed a planet so dangerously close to Tabby’s Star in the first place? A short cosmic distance away—1,000 Astronomical Units, or 1,000 times the distance from the Earth to the Sun—Tabby may have a companion star, perhaps half its size, explains Metzger. “It’s possible that outer star is giving periodic gravitational kicks to the planets around Tabby’s Star,” he says.
The Dyson Sphere still remains a hypothetical contender in the endeavor to explain Tabby’s mystery. But Metzger believes that Tabby’s Star might not be so rare. The Kepler telescope, which found Tabby’s Star, only looked at 100,000 stars in a small part of the sky, which is not too many, he says. But if all the stars in the galaxy, or beyond, were observed, millions of other planet-consuming stars might be found that also produce this curious light-dimming effect.
Otherwise, says Metzger, “You would have to believe that there are a million other alien civilizations assembling Dyson Spheres right now.”
Patrick Rowan's Skywatch: Is alien megastructure blocking this star's light?
Radio telescopes of the Allen Telescope Array used by SETI are seen in Hat Creek, Calif.
Whatever is going on, it is strange. A deep space mystery this big hasn't cropped up since the discovery of pulsars half a century ago.
A group called Planet Hunters made use of their own eyes (as opposed to computer algorithms) to identify unusual dips in the graphs of one particular star's light. One dip revealed a 22 percent drop in brightness. a very big deal.
The star KIC 8462852 was observed over time by the Kepler Space Telescope as part of its search for extrasolar planets. Some refer to KIC 8462852 as Tabby's star, after Tabetha Boyajian, the lead author of the paper detailing this find. For simplicity, I will do that here.
The paper, by the way, is subtitled: "Where's the Flux", affectionately abbreviated "WTF" for the puzzling data. The magnitude of the dips in brightness and irregular patterns can't be explained by planets orbiting the star, so more exotic models, including clouds of comets disturbed by a passing star, have been proposed.
What internet message boards are abuzz over however, is speculation that these light dips may be evidence of some massive megastructure around that star built by an alien civilization. It sounds like science fiction. But is it?
On Oct. 19, the SETI Institute began searching for possible radio emissions from the vicinity of Tabby's star using the Allen Telescope Array in California. Optical telescopes around the world are also seeking additional dimming events, which could tell us whether it was gas, dust, or solid obscuring the star's light. Solid would boost the case for alien construction.
Would we really be surprised? No doubt. Should we be? Maybe not.
Last week, I talked about this with Dr. Steve Lord, an astronomer I first met at the Five College Radio Astronomy Observatory (FCRAO) based in Amherst, MA in the 1970's. Back then, he was already designing his own search of the galactic axis for extraterrestrial signals, and has been working in various aspects of astrobiology and SETI ever since.
Lord, currently with the SETI Institute, has helped quantify the existence of pre-biotic chemistry in interstellar space here and in other galaxies. "The conditions that formed life on the Earth, are omnipresent in the universe" he said. "The carbon, nitrogen, oxygen, iron. the chemistry of all the galaxies varies, but is pretty similar."
Lord believes Tabby's star will have a natural explanation, but also that life is everywhere in the universe. "I don't think we're special. In fact its a little scary because about half the sun-like stars were born before our sun -- and we're talking about billions of years, so there could be civilizations billions of years older than our Earth civilization" he speculated.
That sounds like ɺ long, long time ago, in a galaxy far, far away. ' But will humans progress so far? "We could annihilate ourselves in about a hundred years" Lord warns, "but (non-human) life on Earth is very difficult to annihilate. sort of like locker room toe rot. It's hard to repress." Microbes on earth are able to survive and thrive in environments too hostile for us, so they probably dominate the life-scape of our universe.
Many researchers are excited about Tabby's star, but caution that the "alien solution" remains unlikely. Another star with odd but less dramatic light curves (KIC 4110611) proved to be part of a five-star system. History is filled with such warnings.
In the late 1950's and early 1960's, astronomers detected radio signals (and eventually light) from sources 12 billion light years and more away. Something out there was producing more energy than entire galaxies, yet their output changed more quickly than a single star could. The ET hypothesis was briefly bandied about, but now we call these quasars. Powered by supermassive black holes busy vacuuming up matter in the cores of distant galaxies, they send blasts of radiation through the cosmos.
In 1967, astronomers discovered sharp radio pulses that were initially dubbed LGMs (Little Green Men) because nothing known in nature could produce such signals. The explanation involves one of the universe's most bizarre objects, the rotating neutron star. These impossibly compact and magnetic orbs force their emissions into beams that sweep through space like cosmic lighthouses. These are pulsars. No ET here, but a surprise nonetheless.
The legendary "Wow!" signal of 1977 is more ambiguous. Named for the exclamation written and circled in the margin of a computer printout by Jerry Ehman, the signal filled the entire 72 second observing window (constrained by Earth's rotation) that the Big Ear radio telescope at Ohio State University was capable of. Despite repeated efforts, astronomers have never seen it again.
We "answered" with a message to Sagittarius in 2012, using the giant Arecibo telescope in Puerto Rico. Thirty eight years earlier, in 1974, the first and most powerful broadcast ever deliberately beamed into space was also from Arecibo, and sent toward the globular cluster M-13. Those radio waves have swept over hundreds of star systems, but any aliens listening would only get a one-off similar to the "Wow!" event. The 2012 Arecibo broadcast has not reached any stars yet.
So, was the "Wow!" signal from aliens? Maybe. But there are, of course, other possibilities.
Lord's involvement began with a paper about the signal by Robert Gray. He remembers tossing and turning in his room at UMass, "wondering what I should do" and ultimately recommending that the journal Nature reject the report.
"You can't make claims of extraterrestrial contact so easily" Lord told me, adding that "proof of the origin of the extraterrestrial signal was not strong." He was also troubled that the signal frequency was "so precisely matched to the filter bank, suspiciously pointing to instrumental effects."
He also noted that the signal did not repeat, and the star region it appears to have originated from is not unique. So in the end, caution won out. "The field needs to be solid" he said, then chuckling "I repressed the announcement that we found alien life in my graduate career!" How many people can claim that?
There were no hard feelings, and Lord even helped with Gray's book "The Elusive Wow: Searching for Extraterrestrial Intelligence". Gray has devoted much of his life to finding a repeat of that signal. "He's got six hours on the VLA (Very Large Array) next month" Lord announced with enthusiasm.
Regarding Tabby's Star, Lord calls this event "unprecedented, because it's one of maybe 150,000 cases of Kepler light curves." Regarding the speculation, he says "We don't reject the guy who's got megastructures, we don't reject the guy who's got comet capture. We say, 'you guys have got theories. Let's go forward. What does your theory predict should happen next year?'"
"This is the freedom of the scientific method" he said. "It's open, not closed. It says you shouldn't trust one idea. You should test an idea against observations."
The possibility of some megastructure built by an advanced civilization around an otherwise ordinary star is exciting, but doubtful. Still, it's harder to contemplate the heavens without thoughts of ET today than even a few years ago. Lord calls himself "delusionally optimistic", guessing that "we will find evidence of extraterrestrial life in our lifetimes."
"We're just in our babyhood" he observes, "We're just reaching out. we're going to enter the galactic club eventually."
So now may be a good time to ask yourself how differently would you see the night sky if that were to happen, say, next week. Tabby's star is in the constellation Cygnus, which moves from overhead to the west these evenings. It is 1465 light years away. Do you suppose that's far enough?
Find rise and set times for the sun and moon, and follow ever-changing celestial highlights in the Skywatch section of the Weather Almanac in The Republican and Sunday Republican.
Patrick Rowan has written Skywatch for The Republican since 1987 and has been a Weather Almanac contributor since the mid 1990s. A native of Long Island, Rowan graduated from Northampton High School, studied astronomy at the University of Massachusetts-Amherst in the ❰s and was a research assistant for the Five College Radio Astronomy Observatory. From 1981 to 1994, Rowan worked at the Springfield Science Museum's Seymour Planetarium, most of that time as planetarium manager. Rowan lives in the Florence section of Northampton with his wife, Clara, and cat, Luna.
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Tabby’s Star Megastructure Mystery Continues To Intrigue
Last fall, astronomers were surprised when the Kepler mission reported some anomalous readings from KIC 8462852 (aka. Tabby’s Star). After noticing a strange and sudden drop in brightness, speculation began as to what could be causing it – with some going so far as to suggest that it was an alien megastructure. Naturally, the speculation didn’t last long, as further observations revealed no signs of intelligent life or artificial structures.
But the mystery of the strange dimming has not gone away. What’s more, in a paper posted this past Friday to arXiv, Benjamin T. Montet and Joshua D. Simon (astronomers from the Cahill Center for Astronomy and Astrophysics at Caltech and the Carnegie Institute of Science, respectively) have shown how an analysis of the star’s long-term behavior has only deepened the mystery further.
To recap, dips in brightness are quite common when observing distant stars. In fact, this is one of the primary techniques employed by the Kepler mission and other telescopes to determine if planets are orbiting a star (known as Transit Method). However, the “light curve” of Tabby’s Star – named after the lead author of the study that first detailed the phenomena (Tabetha S. Boyajian) – was particularly pronounced and unusual.
According to the study, the star would experience a
20% dip in brightness, which would last for between 5 and 80 days. This was not consistent with a transitting planet, and Boyajian and her colleagues hypothesized that it was due to a swarm of cold, dusty comet fragments in a highly eccentric orbit accounted for the dimming.
However, others speculated that it could be the result of an alien megastructure known as Dyson Sphere (or Swarm), a series of structures that encompass a star in whole or in part. However, the SETI Institute quickly weighed in and indicated that radio reconnaissance of KIC 8462852 found no evidence of technology-related radio signals from the star.
Other suggestions were made as well, but as Dr. Simon of the Carnegie Institute of Science explained via email, they fell short. “Because the brief dimming events identified by Boyajian et al. were unprecedented, they sparked a wide range of ideas to explain them,” he said. “So far, none of the proposals have been very compelling – in general, they can explain some of the behavior of KIC 8462852, but not all of it.”
To put the observations made last Fall into a larger context, Montet and Simon decided to examine the full-frame photometeric images of KIC 8462852 obtained by Kepler over the last four years. What they found was that the total brightness of the star had been diminishing quite astonishingly during that time, a fact which only deepens the mystery of the star’s light curve.
Photometry of KIC8462852 obtained by the Kepler mission, showing a period of more rapid decline during the later period of observation. Credit: Montet & Simon 2016
As Dr. Montet told Universe Today via email:
“Every 30 minutes, Kepler measures the brightness of 160,000 stars in its field of view (100 square degrees, or approximately as big as your hand at arm’s length). The Kepler data processing pipeline intentionally removes long-term trends, because they are hard to separate from instrumental effects and they make the search for planets harder. Once a month though, they download the full frame, so the brightness of every object in the field can be measured. From this data, we can separate the instrumental effects from astrophysical effects by seeing how the brightness of any particular star changes relative to all its neighboring stars.”
Specifically, they found that over the course of the first 1000 days of observation, the star experienced a relatively consistent drop in brightness of 0.341% ± 0.041%, which worked out to a total dimming of 0.9%. However, during the next 200 days, the star dimmed much more rapidly, with its total stellar flux dropping by more than 2%.
For the final 200 days, the star’s magnitude once again consistent and similar to what it was during the first 1000 – roughly equivalent to 0.341%. What is impressive about this is the highly anomalous nature of it, and how it only makes the star seem stranger. As Simon put it:
“Our results show that over the four years KIC 8462852 was observed by Kepler, it steadily dimmed. For the first 2.7 years of the Kepler mission the star faded by about 0.9%. Its brightness then decreased much faster for the next six months, declining by almost 2.5% more, for a total brightness change of around 3%. We haven’t yet found any other Kepler stars that faded by that much over the four-year mission, or that decreased by 2.5% in six months.”
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Of the over 150,000 stars monitored by the Kepler mission, Tabby’s Starr is the only one known to exhibit this type of behavior. In addition, Monetet and Cahill compared the results they obtained to data from 193 nearby stars that had been observed by Kepler, as well as data obtained on 355 stars with similar stellar parameters.
From this rather large sampling, they found that a 0.6% change in luminosity over a four year period – which worked out to about 0.341% per year – was quite common. But none ever experienced the rapid decline of more than 2% that KIC 8462852 experienced during that 200 days interval, or the cumulative fading of 3% that it experienced overall.
Montet and Cahill looked for possible explanations, considering whether the rapid decline could be caused by a cloud of transiting circumstellar material. But whereas some phenomena can explain the long-term trend, and other the short-term trend, no one explanation can account for it all. As Montet explained:
“We propose in our paper that a cloud of gas and dust from the remnants of a planetesimal after a collision in the outer solar system of this star could explain the 2.5% dip of the star (as it passes along our line of sight). Additionally, if some clumps of matter from this collision were collided into high-eccentricity comet-like orbits, they could explain the flickering from Boyajian et al., but this model doesn’t do a nice job of explaining the long-term dimming. Other researchers are working to develop different models to explain what we see, but they’re still working on these models and haven’t submitted them for publication yet. Broadly speaking, all three effects we observe cannot be explained by any known stellar phenomenon, so it’s almost certainly the result of some material along our line of sight passing between us and the star. We just have to figure out what!”
So the question remains, what accounts for this strange dimming effect around this star? Is there yet some singular stellar phenomena that could account for it all? Or is this just the result of good timing, with astronomers being fortunate enough to see a combination of a things at work in the same period? Hard to say, and the only way we will know for sure is to keep our eye on this strangely dimming star.
And in the meantime, will the alien enthusiasts not see this as a possible resolution to the Fermi Paradox? Most likely!
Did Astronomers Find Evidence of an Alien Civilization? (Probably Not. But Still Cool.)
A paper by a team of astronomers is getting some notice because of aliens.
Now let’s have a care here. The paper doesn’t mention aliens, and it doesn’t even imply aliens. Not directly, at least. But the astronomers found a star so odd, with behavior so difficult to explain, that it’s clear something weird is happening there. And some of the astronomers who did the work are now looking into the idea that what they’ve found might (might!) be due to aliens.
But don’t let this idea run away with you (as it has with some folks on social media and, no doubt, will in some sketchier “media” outlets any minute now). The scientists involved are being very skeptical and approaching this the right way: more of an interested “Hey, why not?” follow-up, as opposed to the Hollywood renegade astronomer who just knows it’s aliens but (fist shaking in the air) just can’t convince those uptight Big Astro sellouts!
OK, so first, what’s the science?
The star is called KIC 8462852, and it’s one of more than a hundred thousand stars that was observed by NASA’s Kepler mission. Kepler stared at these stars, looking for dips in their brightness. These very slight dimmings can be due to many factors, but one is if the star has planets, and one (or more) of them orbits the star in such a way that it passes directly in front of the star as seen from Earth. If it does—what we call a transit—we see a tiny diminution of starlight, usually by less than a percent.
Thousands of exoplanets have been found this way. Usually the planet is on a short orbit, so the dip we see is periodic, repeating every few days, weeks, or months, depending on the size of the planet’s orbit.
KIC 8462852 is a star somewhat more massive, hotter, and brighter than the Sun. It’s about 1,500 light-years away, a decent distance, so it’s too faint to see with the naked eye. The Kepler data for the star are pretty bizarre: There are dips in the light, but they aren’t periodic. They can be very deep one dropped the amount of starlight by 15 percent, and another by a whopping 22 percent!
Straight away, we know we’re not dealing with a planet here. Even a Jupiter-sized planet only blocks roughly 1 percent of this kind of star’s light, and that’s about as big as a planet gets. It can’t be due to a star, either we’d see it if it were. And the lack of a regular, repeating signal belies both of these as well. Whatever is blocking the star is big, though, up to half the width of the star itself!
Also, it turns out there are lots of these dips in the star’s light. Hundreds. And they don’t seem to be periodic at all. They have odd shapes to them, too. A planet blocking a star’s light will have a generally symmetric dip the light fades a little, remains steady at that level, then goes back up later. The dip at 800 days in the KIC 8462852 data doesn’t do that it drops slowly, then rises more rapidly. Another one at 1,500 days has a series of blips up and down inside the main dips. There’s also an apparent change in brightness that seems to go up and down roughly every 20 days for weeks, then disappears completely. It’s likely just random transits, but still. It’s bizarre.
The authors of the paper went to some trouble to eliminate obvious causes. It’s not something in the telescope or the processing the dips are real. It’s not due to starspots (like sunspots, but on another star). My first thought was some sort of planetary collision, like the impact that created the Moon out of the Earth billions of years ago that would create a lot of debris and dust clouds. These chunks and clouds orbiting the star would then cause a series of transits that could reproduce what’s seen.
Drawing by NASA/JPL-Caltech/T. Pyle (SSC)
The problem with that is that there’s no excess of infrared light from the star. Dust created in such impacts warms up and glows in the IR. We know how much IR stars like KIC 8462852 give off, and we see just the right amount from it, no more. The lack of that glow means no (or very little) dust.
The last idea the astronomers looked at was a series of comets orbiting the star. These could be surrounded by clouds of gas and other material that could produce the dips seen. The lack of IR is puzzling in that case, but not too damning. If another star happened to pass nearby, then its gravity could disturb the first star’s Oort cloud, the region billions of kilometers out where we think most (if not all) stars have billions of icy objects. This disturbance could send these ice chunks flying down toward the star, where they could break up, creating all those weird dips—ices in them would heat up, blow off as a gas, and could explain the odd shapes of the dips detected, too.
And, as it happens, there is another star pretty close to KIC 8462852 a small red dwarf about 130 billion kilometers out. That’s close enough to affect the Oort cloud.
This doesn’t close the case, though. Comets are a good guess, but it’s hard to imagine a scenario where they could completely block 22 percent of the light from a star that’s a huge amount. Really huge.
So where does that leave us?
Wondering if there might be more to this, Tabetha Boyajian, the lead author on the paper, showed the results to Jason Wright, an astronomer who studies exoplanets and, not coincidentally, has researched how to look for signatures of advanced alien civilizations in Kepler data.
Look at our own civilization. We consume ever-increasing amounts of power, and are always looking for bigger sources. Fossil, nuclear, solar, wind … Decades ago, physicist Freeman Dyson popularized an interesting idea: What if we built thousands of gigantic solar panels, kilometers across, and put them in orbit around the Sun? They’d capture sunlight, convert it to energy, and that could be beamed to Earth for our use. Need more power? Build more panels! An advanced civilization could eventually build millions, billions of them.
This idea evolved into what’s called a Dyson Sphere, a gigantic sphere that completely encloses a star. It was popular back in the 1970s and 80s there was even an episode of Star Trek: The Next Generation about one. Dyson never really meant that we’d build an actual sphere just lots of little panels that might mimic one.
But it raises an interesting possibility for detecting alien life. Such a sphere would be dark in visible light but emit a lot of infrared. People have looked for them, but we’ve never seen one (obviously).
Which brings us back to KIC 8462852. What if we caught an advanced alien civilization in the process of building such an artifact? Huge panels (or clusters of them) hundreds of thousands of kilometers across, and oddly-shaped, could produce the dips we see in that star’s light.
Now I imagine some of you might expect me to rail against this idea, call it ridiculous, and pooh-pooh the notion of aliens and all that
This photo is an Internet meme and is everywhere. This specific instance is from Quickmeme.
Well, surprise! I actually kinda like it. I’m not saying it’s right, mind you, just that it’s interesting. Wright isn’t some wild-eyed crackpot he’s a professional astronomer with a solid background. As he told me when I talked to him over the phone, there’s “a need to hypothesize, but we should also approach it skeptically” (paraphrasing a tweet by another astronomer, David Grinspoon), with which I wholeheartedly agree.
Look, I think it’s pretty obvious this scenario is, um, unlikely. But hey, why not? It’s easy enough to get follow-up observations of the star to check the idea out. It’s low probability but high stakes, so probably worth a shot. And it’s not exactly science fiction Wright and a few other astronomers have submitted a paper (pending publication) to the prestigious Astrophysical Journal examining the physics of these structures and detailing how they could be detected around other stars.
As reported in the Atlantic (which is what started all the social media interest in the first place), Wright and Boyajian are indeed proposing to use a radio telescope to look for signals from the star. An alien civilization building such a structure might leak (or broadcast!) radio waves that could be detectable from 1,500 light-years away. That’s the whole basis of SETI, the Search for Extraterrestrial Intelligence (see the movie Contact, or better yet read the book, for more on this). Telescope time is controlled by a committee, and it’s not clear if the proposal will pass or not. I hope so it shouldn’t take too much telescope time, and under modest assumptions it shouldn’t be too hard to detect a signal.
If one exists. This is still a very, very long shot. But again, this isn’t a huge effort costing zillions of dollars. The effort is minimal, but the payoff could be pretty big. Also, radio observations of the star might prove useful in solving the mystery, even if it’s not aliens. Which, I’ll reiterate, it really likely isn’t.
I would also support follow-up observations (as indicated in the Boyajian paper) looking for signals from comets. Some molecules in comets glow quite brightly when comets get near a star, and that signal may not be too difficult to detect either. Also, there could simply be natural possibilities no one has thought of yet. More observations means stirring the pot a little more and could inspire new thinking.
Whether there are aliens constructing huge megastructures to feed their power needs at KIC 8462852, or—overwhelmingly more likely—it’s a more natural scenario, this is a pretty weird and interesting star. And it’s definitely worth investigating further.
Alien megastructure? Forget about it, weird star’s discoverers say after further study
Astronomer Tabetha Boyajian discusses Tabby’s Star, “the most mysterious star in the universe,” during a TED talk in February 2016 in Vancouver, B.C. (TED via YouTube)
The astronomers who once speculated that an alien megastructure might be responsible for the weirdly fluctuating light from a distant star have now fully ruled out that way-out explanation.
Their conclusion, reported in a paper published today by Astrophysical Journal Letters, is based on a crowdfunded analysis of the light patterns in a wide range of wavelengths.
The authors of the paper include Louisiana State University’s Tabetha Boyajian, who led the discovery team for the star known as KIC 8462852 or “Tabby’s Star” and Penn State’s Jason Wright, who first proposed the alien-megastructure hypothesis.
Tabby’s Star was discovered about 1,500 light-years away in the constellation Cygnus, thanks to an analysis of data from NASA’s Kepler space telescope. Soon after the discovery was announced in 2015, it was dubbed the “most mysterious star in the universe,” because its brightness underwent dramatic dips over intervals ranging from five to 80 days.
Wright suggested that the variations in brightness might be due to the blocking effect of a huge structure that was built around the star. He acknowledged that the presence of an alien megastructure, such as a Dyson sphere, was highly unlikely. Nevertheless, he and his colleagues thought the hypothesis was worth checking out.
“We were hoping that once we finally caught a dip happening in real time, we could see if the dips were the same depth at all wavelengths,” he explained today in a news release. “If they were nearly the same, this would suggest that the cause was something opaque, like an orbiting disk, planet, or star, or even large structures in space.”
This chart shows variations in the brightness of the star KIC 8462852 between May 2017 and December 2017, as recorded by telescopes in Texas (ELP), Hawaii (OGG) and the Canary Islands (TFN). Significant dips have been nicknamed Elsie, Celeste, Skara Brae and Angkor. (Boyajian et al.)
To help pay for the observations and analysis, Wright and his colleagues raised more than $100,000 in a Kickstarter campaign.
A network of telescopes around the world, coordinated through the Las Cumbres Observatory in California, detected four sustained dips in the starlight between March 2016 and December 2017. The team went so far as to name each of the dips. The first two were called Elsie and Celeste, while the latter two were named after lost cities (Skara Brae in Scotland and Angkor in Cambodia).
The authors wrote that as far as they were concerned, the dips in brightness had some things in common with those lost cities.
“They’re ancient we are watching things that happened more than 1,000 years ago,” they said. “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?”
When the light levels in various wavelengths were measured, Tabby’s Star became a little less mysterious. The team found that the dimming was much less pronounced in some wavelengths than in others.
“Dust is most likely the reason why the star’s light appears to dim and brighten,” Boyajian said. “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.”
A healthy amount of mystery still remains.
“The latest research rules out alien megastructures, but it raises the probability of other phenomena being behind the dimming,” Wright said. “There are models involving circumstellar material — like exocomets, which were Boyajian’s team’s original hypothesis — which seem to be consistent with the data we have.”
There’s also a chance that the dimming is being caused by an as-yet-unknown stellar phenomenon rather than a band of dust or a swarm of comets that’s blocking the starlight.
Boyajian said the discovery and study of KIC 8462852 should be seen as a certifiable win for citizen-backed astronomy, even though it turns out aliens aren’t involved. She pointed out that the star would never have been studied if it weren’t for its discovery by volunteers in the Planet Hunters citizen-science campaign, the interest from more than 200 astronomers, and the support of more than 1,700 Kickstarter donors.
“It’s exciting,” she said. “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.”
KIC 8462852 may be known as Tabby’s Star, but it turned out to be a star the whole world could claim.
Boyajian is the principal author of the paper in Astrophysical Journal Letters, titled “The First Post-Kepler Brightness Dips of KIC 8462852.” Co-authors include James Davenport of Western Washington University, who is also a DIRAC Fellow at the University of Washington. To trace the history of the mystery (or donate to the cause), check out the project website, which is called “KIC 8462852: Where’s the Flux?”
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.
The "alien" point of light in the sky is known as Tabby's star, which was named after Tabetha Boyajian, the Louisiana State University astrophysicist who in 2015 first noticed the unusual patterns in its starlight that others initially attributed to alien construction projects. Boyajian noticed that the star tended to dip in brightness at odd intervals, sometimes slightly and sometimes by significant fractions of its total light. It was also slowly losing brightness over time. She later called it in a TED Talk the "most mysterious star in the universe" because no straightforward astrophysical theory could explain the dimming pattern &mdash though she also expressed skepticism about suggestions that the dimming was the result of a "megastructure" constructed around the star by an advanced civilization.
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.
Over the course of millions of years, that material would form an irregular cloud around the star along the orphaned moon's eccentric orbit, he told Live Science, adding that such a cloud would periodically block some of the star&rsquos light from reaching Earth &mdash just like the effect originally attributed to a Dyson sphere megastructure.
They suspect an orphaned moon, as opposed to a planet, is off-gassing the cloud, because it's difficult to explain how an icy planet could end up in that irregular orbit in the first place. Based on our own solar system, he said, scientists know that solid, rocky bodies tend to make up the inner parts of a system, while bigger, gaseous planets dominate the outer system. And those planets are often orbited by icy moons.
Metzger and his colleagues described orbital calculations in which a planet like Jupiter, orbited by large moons and following an eccentric orbit, gets knocked (perhaps by another nearby star) into a collision course with its host star. As it falls to its doom, the star would rip those moons from their orbits. Most of the moons would fall into the star or fly out of the system, they showed, but in about 10% of all cases, a moon would end up in an eccentric orbit. And, critically, that orbit would likely place the moon within its star's "ice line" &mdash the point within which the star's radiation would blast ice off the moon's surface.
If the moon were made up of the right materials, they wrote, it would start to break apart due to the increased radiation of its new, closer orbit, spilling that material into interplanetary space like a gargantuan comet. And even though we'd never see the moon with our existing telescopes, that spilled material would form a cloud of dust and gas big enough to block Tabby's star's light in strange and unpredictable ways. Over time, the star would appear to get dimmer and dimmer, just like Tabby's star, as the total amount of dust in its orbit increased.
Nothing's certain, of course. Metzger said it's still possible some other phenomenon is creating the effect. But this moon theory offers a compelling explanation for a distant flickering once chalked up (at least in the popular press) to aliens.
The paper, available as a draft online in the preprint journal arXiv, will be published in a forthcoming issue of the journal Monthly Notices of the Royal Astronomical Society.
'Alien Megastructure' Star Is at It Again with the Strange Dimming
The perplexing cosmic object known as "Boyajian's star" is once again exhibiting a mysterious pattern of dimming and brightening that scientists have tried to explain with hypotheses ranging from swarms of comets to alien megastructures.
Today (May 19), an urgent call went out to scientists around the world to turn as many telescopes as possible toward the star, to try and crack the mystery of its behavior.
"At about 4 a.m. this morning I got a phone call … that Fairborn [Observatory] in Arizona had confirmed that the star was 3 percent dimmer than it normally is," Jason Wright, an associate professor of astronomy at Pennsylvania State University, who is managing a study of Boyajian's star, said during a live webcast today at 2 p.m. EDT (1800 GMT). "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."
Star KIC 8462852, or Boyajian's star (also nicknamed "Tabby's star," for astronomer Tabetha Boyajian, who led the team that first detected the star's fluctuations), has demonstrated an irregular cycle of growing dimmer and then returning to its previous brightness. These changes were first spotted in September 2015 using NASA's Kepler Space Telescope, which was built to observe these kinds of dips in a star's brightness, because they can be caused by a planet moving in front of the star as seen from Earth.
But the brightness changes exhibited by Boyajian don't show the kind of regularity that is typical of a planet's orbit around its star, and scientists can't see how the changes could be explained by a system of planets.
Scientists have hypothesized that the changes could be due to a swarm of comets passing in front of the star, that they're the result of strong magnetic activity, or that it's some massive structure built by aliens. But no leading hypothesis has emerged, so scientists have been eager to capture a highly detailed picture of the light coming from the star during one of these dimming periods. This detailed view is what scientists typically call an object spectra. It can reveal, for example, the specific chemical elements that are in a gas. It can also tell scientists if an object is moving toward or away from the observer.
"Whatever's causing the star to get dimmer will leave a spectral fingerprint behind," Wright said during the webcast, which took place in the Breakthrough Listen laboratory at the University of California, Berkeley. "So if there is a lot of dust between us and the star … it will block more blue light than red light. If there is gas in that dust, that gas should absorb very specific wavelengths and we should be able to see that. And so, we've been eager to see one of these changes in one of these dips of the star so we can take some spectra."
But the scientists couldn't predict when the next dimming event would occur or how long it will last. (Dips detected by Kepler lasted for between two and seven days, according to Wright.) Professional-grade telescopes typically schedule observing time weeks or months in advance, so Wright and his colleagues knew their observations would have to come at the behest of colleagues who were already using the telescopes for other projects.
"We need to have a network of people around the world that are ready to jump on [and observe it]," Wright said. "Fortunately, Tabby's star is not too faint and so there are a lot of observers and telescopes … that have graciously agreed to take some time out of their science to grab a spectrum for us [tonight]."
Wright said the call had gone out to amateur as well as professional astronomers to observe Boyajian's star during this dimming period. The largest and most powerful telescopes that will heed the call are the twin 10-meter telescopes at the W.H. Keck Observatory in Hawaii. The team is working to gain observing time on at least three other large telescopes on the U.S., according to Wright.
The Breakthrough Listen initiative, which searches for signs of intelligent life in the universe, has also taken an interest in the star and will be observing it with the Automated Planet Finder telescope at Lick Observatory in California, according to Andrew Siemion, director or the Berkeley SETI Research Center, said in the webcast.
"It's Super Bowl Sunday," Siemion said of the atmosphere at the during the webcast. "There's a palpable tension."
Breakthrough and the Berkeley center are now trying to get some observing time on the Green Bank radio telescope in West Virginia, according to Siemion.