Something other than a transiting planet makes the Kepler star KIC fluctuate wildly and unpredictably in brightness. Astronomers suspect a shattered comet, but who knows? Credit: NASA

What’s Orbiting KIC 8462852 – Shattered Comet or Alien Megastructure?

Article Updated: 23 Dec , 2015

by

“Bizarre.” “Interesting.” “Giant transit”.  That were the reactions of Planet Hunters project volunteers when they got their first look at the light curve of the otherwise normal sun-like star KIC 8462852 nearly.

Of the more than 150,000 stars under constant observation during the four years of NASA’s primary Kepler Mission (2009-2013), this one stands alone for the inexplicable dips in its light. While almost certainly naturally-caused, some have suggested we consider other possibilities.

Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist's conception of a simultaneous transit of three planets observed by NASA's Kepler spacecraft on Aug. 26, 2010. Image credit: NASA/Tim Pyle

Kepler-11, a sun-like star orbited by six planets. At times, two or more planets pass in front of the star at once, as shown in this artist’s conception of a simultaneous transit of three planets observed by the Kepler spacecraft on Aug. 26, 2010. During each pass or transit, the star’s light fades in a periodic way. 
Credit: NASA/Tim Pyle

You’ll recall that the orbiting Kepler observatory continuously monitored stars in a fixed field of view focused on the constellations Lyra and Cygnus hoping to catch  periodic dips in their light caused by transiting planets. If a drop was seen, more transits were observed to confirm the detection of a new exoplanet.

And catch it did. Kepler found 1,013 confirmed exoplanets in 440 star systems as of January 2015 with 3,199 unconfirmed candidates. Measuring the amount of light the planet temporarily “robbed” from its host star allowed astronomers to determine its diameter, while the length of time between transits yielded its orbital period.

Graph showing the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude. Credit: Boyajian et. all

Graph showing 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

Volunteers with the Planet Hunters project, one of many citizen science programs under the umbrella of Zooniverse, harness the power of the human eye to examine Kepler light curves (a graph of a star’s changing light intensity over time), looking for repeating patterns that might indicate orbiting planets. They were the first to meet up with the perplexing KIC 8462852.

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A detailed look at a small part of the star’s light curve reveals an unknown, regular variation of its light every 20 days. Superimposed on that is the star’s 0.88 day rotation period. Credit: Boyajian et. all

This magnitude +11.7 star in Cygnus, hotter and half again as big as the Sun, showed dips all over the place. Around Day 800 during Kepler’s run, it faded by 15% then resumed a steady brightness until Days 1510-1570, when it underwent a whole series of dips including one that dimmed the star by 22%. That’s huge! Consider that an exo-Earth blocks only a fraction of a percent of a star’s light; even a Jupiter-sized world, the norm among extrasolar planets, soaks up about a percent.

Exoplanets also show regular, repeatable light curves as they enter, cross and then exit the faces of their host stars. KIC 8462852’s dips are wildly a-periodic.

Could a giant comet breakup followed by those pieces crumbling into even smaller comets be the reason for KIC's erratic changes in brightness? Credit: NASA

Could a giant comet breakup and subsequent cascading breakups of those pieces be behind KIC 8462852’s erratic changes in brightness? Credit: NASA

Whatever’s causing the flickering can’t be a planet. With great care, the researchers ruled out many possibilities: instrumental errors, starspots (like sunspots but on other stars), dust rings seen around young, evolving stars (this is an older star) and pulsations that cover a star with light-sucking dust clouds.

What about a collision between two planets? That would generate lots of material along with huge clouds of dust that could easily choke off a star’s light in rapid and irregular fashion.

A great idea except that dust absorbs light from its host star, warms up and glows in infrared light. We should be able to see this “infrared excess” if it were there, but instead KIC 8462852 beams the expected amount of infrared for a star of its class and not a jot more. There’s also no evidence in data taken by NASA’s Wide-field Infrared Survey Explorer (WISE) several years previously that a dust-releasing collision happened around the star.

Our featured star shines around 12th magnitude in the constellation Cygnus the Swan (Northern Cross) high in the southern sky at nightfall this month. A 6-inch or larger telescope will easily show it. Use this map to get oriented and the map below to get there. Source: Stellarium

Our featured star shines at magnitude +11.7 in the constellation Cygnus the Swan (Northern Cross) high in the southern sky at nightfall this month. A 6-inch or larger telescope will easily show it. Use this map to get oriented and the map below to get there. Source: Stellarium

After examining the options, the researchers concluded the best fit might be a shattered comet that continued to fragment into a cascade of smaller comets. Pretty amazing scenario. There’s still dust to account for, but not as much as other scenarios would require.

Detailed map showing stars to around magnitude 12 with the Kepler star identified. It's located only a short distance northeast of the open cluster NGC 6886 in Cygnus. North is up. Source: Chris Marriott's SkyMap

Detailed map showing stars to around magnitude 12 with the Kepler star identified. It’s located only a short distance northeast of the open cluster NGC 6886 in Cygnus. North is up. Click to enlarge. Source: Chris Marriott’s SkyMap

Being fragile types, comets can crumble all by themselves especially when passing exceptionally near the Sun as sungrazing comets are wont to do in our own Solar System. Or a passing star could disturb the host star’s Oort comet cloud and unleash a barrage of comets into the inner stellar system. It so happens that a red dwarf star lies within about 1000 a.u. (1000 times Earth’s distance from the Sun) of KIC 8462852. No one knows yet whether the star orbits the Kepler star or happens to be passing by. Either way, it’s close enough to get involved in comet flinging.

So much for “natural” explanations. Tabetha Boyajian, a postdoc at Yale, who oversees the Planet Hunters and the lead author of the paper on KIC 8462852, asked Jason Wright, an assistant professor of astronomy at Penn State, what he thought of the light curves. “Crazy” came to mind as soon he set eyes on them, but the squiggles stirred a thought. Turns out Wright had been working on a paper about detecting transiting megastructures with Kepler.

There are Dyson rings and spheres and this, an illustration of a Dyson swarm. Could this or a variation of it be what we're detecting around KIC? Not likely, but a fun thought experiment. Credit: Wikipedia

There are Dyson rings and spheres and a Dyson swarm depicted here. Could this or a variation of it be what we’re seeing around KIC 8462852? Not likely, but a fun thought experiment. Credit: Wikipedia

In a recent blog, he writes: “The idea is that if advanced alien civilizations build planet-sized megastructures — solar panels, ring worlds, telescopes, beacons, whatever — Kepler might be able to distinguish them from planets.” Let’s assume our friendly aliens want to harness the energy of their home star. They might construct enormous solar panels by the millions and send them into orbit to beam starlight down to their planet’s surface. Physicist Freeman Dyson popularized the idea back in the 1960s. Remember the Dyson Sphere, a giant hypothetical structure built to encompass a star?

From our perspective, we might see the star flicker in irregular ways as the giant panels circled about it. To illustrate this point, Wright came up with a wonderful analogy:

“The analogy I have is watching the shadows on the blinds of people outside a window passing by. If one person is going around the block on a bicycle, their shadow will appear regularly in time and shape (like a regular transiting planet). But crowds of people ambling by — both directions, fast and slow, big and large — would not have any regularity about it at all.  The total light coming through the blinds might vary like — Tabby’s star.”

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 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. Credit: NRAO/AUI/NSF

Even Wright admits that the “alien hypothesis” should be seen as a last resort. But to make sure no stone goes  unturned, Wright, Boyajian and several of the Planet Hunters put together a proposal to do a radio-SETI search with the Green Bank 100-meter telescope. In my opinion, this is science at its best. We have a difficult question to answer, so let’s use all the tools at our disposal to seek an answer.

Star with a mystery, KIC 8462852, photographed on Oct. 15, 2015. Credit: Gianluca Masi

KIC 8462852, photographed on Oct. 15, 2015. It’s an F3 V star (yellow-white dwarf) located about 1,480 light years from Earth. Credit: Gianluca Masi

In the end, it’s probably not an alien megastructure, just like the first pulsar signals weren’t sent by LGM-1 (Little Green Men). But whatever’s causing the dips, Boyajian wants astronomers to keep a close watch on KIC 8462852 to find out if and when its erratic light variations repeat. I love a mystery, but  answers are even better.

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N70SAK
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N70SAK
October 16, 2015 11:46 AM

Calling Louis Wu!

LouisWu
Member
LouisWu
October 18, 2015 4:29 AM

What do you think you are a pearson puppeteer?

robst247
Member
October 16, 2015 2:24 PM

If these massive dips in brightness are not occuring periodically there’s no reason to think that the obscuring objects are orbiting the star in question. Exit silly alien megastructure / ‘Dyson sphere’ hypothesis. What about rogue black dwarfs (dead stars that emit neither light nor heat radiation) drifting far from KIC 8462852 and coincidentally crossing our line of sight to that star?

Qev
Member
Qev
October 16, 2015 2:48 PM

These would actually cause the star to brighten due to lensing, IIRC?

robst247
Member
October 16, 2015 2:59 PM

IIRC = if I reason correctly?
Would such a small star have enough gravity to cause lensing? Anyway, black dwarfs can’t exist, and a single cold object drifting in interstellar space wouldn’t cause the cluster of dips. I don’t accept the comet-that-broke-apart theory either. Too small. It IS perplexing.
Anybody got a brilliant theory?

SteveZodiac
Member
SteveZodiac
October 17, 2015 8:58 AM

Yes, look up exoplanet discovery by microlensing

robst247
Member
October 17, 2015 6:45 PM

SteveZodiac – I found this article on microlensing: http://www.planetary.org/explore/space-topics/exoplanets/microlensing.html?referrer=https://www.google.nl/
BUT – and it’s a big BUT – microlensing causes an UPWARD spike in brightness. Another possible explanation bites the dust.

FarAwayLongAgo
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FarAwayLongAgo
October 16, 2015 2:57 PM

Thin artificial solar panels can be rotated at will, for whatever reason. Cooling? Assembly process? Disarray as a leftover of a demised civilization?

FarAwayLongAgo
Member
FarAwayLongAgo
October 16, 2015 2:54 PM

How could comets cover 22% of a star, an F3 star with 1.58 Solar radius? It can’t be dust because AFAIK that would be seen in IR. So, substantial cometary blocks together corresponding to about a 0.7 solar radius object. In our line of sight all at once. I don’t understand why that is even proposed as a hypothesis.

Why don’t these high albedo icy comets boost the light curve by 10%+ with reflected light when they orbit at the other side of the star?

robst247
Member
October 16, 2015 5:34 PM

I was just watching the Weekly Space Hangout over at UniverseToday.com with Kimberly Cartier at Penn State (http://sites.psu.edu/astrolady/), who is directly involved in this research. The point is not only that the light-curve dips are aperiodic and extreme (Jupiter in front of this star would only cause a 1% dip), but that their profiles are widely variant and asymmetrical! The objects must therefore be irregularly shaped. Huge, irregularly shaped objects – the mind boggles!

Pete
Member
Pete
October 16, 2015 5:54 PM

How far is KIC 8462852? ie: Is there any possibility that improved resolution devices might someday actually resolve the larger-dip-causing elements?
We now have Pluto and Charon proving that binary planets occur. Is it possible that more than one binary (or even tertiary?) planet system orbiting the star could produce the dips we see?
22% dip in the light curve? 15% dip? Wow! Is there a too-dim-to see, multi-star system (with its own groups of multi-planet systems) orbiting this star?
Or all that plus star-spots? What is the maximum theoretical dimming from a star spot or start spot system?
I, for one, am clinging to natural causes.

BlackWolfStanding
Member
BlackWolfStanding
October 16, 2015 5:59 PM

We are possibly seeing a lot of planets orbiting the star. The periods of which would vary so that we are seeing irregular ‘shadows.’ Simple solution is plot all the ‘shadows’ and then measure for periods of equal length. The odd ‘shadows’ are just planets with longer periods than what the combined data has. I’m thinking some of the planets may be huge planetoids that just never formed into one whole planet because of the proximity to a gas giant.

Halley
Member
Halley
October 16, 2015 10:30 PM

Maybe it’s getting ready to nova…

Bo Zo
Member
Bo Zo
October 16, 2015 11:35 PM
None of the proposed explanations sound right to me. Comets, dust, planets, even record setting gas giants, are all too small to account for 20% occlusion. Even a maximum brown dwarf companion seems too small, and I expect a brown dwarf would show detectable variations in the infrared. (Would it?) With brown dwarfs or huge planets, there’d be wobble. And it would hardly be unique. Why no talk of stellar dynamics? Can’t the star be doing it on its own? That seems more reasonable to me than such wild transits. I also thought of this: Maybe something like a pair of brown dwarfs is in the nearby foreground, orbiting each other, occasionally occluding the background star. Brown dwarfs… Read more »
FarAwayLongAgo
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FarAwayLongAgo
October 17, 2015 3:49 AM

Stellar dynamics could maybe solve the periodicity, but astrophysicists have good models for stellar physics, so I don’t think it is a popular suggestion. Maybe it is unusual after some unusual merger history and has been completely wrongly classified. Irregular convections darkening its surface. Although it is nothing like Betelgeuse, it has an irregular light curve too (which is much better understood):

Bo Zo
Member
Bo Zo
October 17, 2015 8:27 AM
Ordinarily I would agree, astrophysicists think they mostly understand stellar dynamics. The problem is, astrophysicists also mostly understand large orbital bodies & comets & such. So whatever this is, it appears to be something less well understood. Either it’s unicorns, or it’s something new about stars or orbital bodies. Stellar dynamics is mostly understood through theory. Practice is always messier. As you suggest, maybe a large planet collided with the star and these are the residual effects – or any other rare event that we haven’t got much experience observing. Or a herd of unicorns. Or it’s just something stars do, but very rarely. How many of these large dimmings have been observed? Just two? If so, however… Read more »
permanently_ad_hoc
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permanently_ad_hoc
October 17, 2015 1:20 AM

Who says planet collisions have to generate observable amounts of dust? Why not two gas giants in some hit-and-run collision? I would guess that would pull out streamers and clumpy clouds. You would need relatively little mass to create large clouds that could dim the star light significantly.

Bo Zo
Member
Bo Zo
October 17, 2015 1:47 AM

That doesn’t sit quite right with me either, but it might turn out to be the best guess. Sounds more likely than aliens or invisible brown dwarfs. (crackpot!) And a belt of irregular gas streamers might account for the irregular transit times and “odd shapes”.

Still, i think you’d need a lot of gas. It would heat quickly and I’d think glow brightly in the IR. I think that’s exactly what they don’t detect.

permanently_ad_hoc
Member
permanently_ad_hoc
October 17, 2015 9:37 PM

I don’t think gas like this would glow in the IR. That is from warm blackbody radiation from solid objects. Atoms or molecules of gas, probably mostly hydrogen from a gas giant, would radiate in discrete lines and then only if its electrons were pumped up by something else. If those discrete lines are there, they might be hard to detect against a background of a zillion other sources. Maybe Mr. King knows if that holds, or not.

sangos
Member
sangos
October 17, 2015 1:52 AM

Excellent Bob your writeup throws up the max info and angles to this extremely curious discovery.

Not planets and NOT comets either NOR any cosmic body. The clues are VARIABLE upto 22% dip in light and IRREGULARLY timed transits. Whatever is going around that star is in an active propelled orbit, made up of multiple shaped objects swinging around with variable orbital distances and is HUMONGOUS to block out half the light of an already massive star. So whats going on folks?!

mewo
Member
mewo
October 17, 2015 1:54 AM

Wouldn’t a partially built alien megastructure also show up in the infrared, for the same reasons that dust would?

I have another objection to the Dyson Sphere hypothesis, and that is why an alien civilisation would want to build one. Could they possibly need that much energy? What would they do with it?

FarAwayLongAgo
Member
FarAwayLongAgo
October 17, 2015 5:20 AM

High energy physics to fuse dark matter into artefacts with unique properties, such as probing the center of a planet or a star unaffected by temperature and pressure? Nature uses high energy, so there are certainly ways to make use of it. But I think you’re right that a Dyson sphere would shine bright in IR. Jason Wright himself (as does Freeman Dyson) says that this is physically unavoidable regardless of technological efficiency. Here’s a SETI talk about how Jason has searched for Dyson spheres:
http://www.seti.org/weeky-lecture/wise-search-large-extraterrestrial-civilizations-complementary-approach-traditional

Btw, do they use microwave ovens near the DSN antenna receiving data from Kepler? ;-D

SteveZodiac
Member
SteveZodiac
October 17, 2015 9:01 AM

Let’s wait for the doppler and spectroscopic studies, that will tell us about the mass of any orbiting objects. Would love it to be aliens (just for the effect on politicians) but if not it could be something very interesting indeed.

Gmack65
Member
Gmack65
October 17, 2015 1:22 PM

Great article Bob!

One question, couldn’t that be an entirely new class of variables, possibly due to a short transition in the life of a star (one that lasts just a few thousand years or so ?)
Do we have already seen (in reality, not just on computer models) what exactly happens when a main sequence star run out of fuel in the nucleus and begins contracting and burning H in the inner shell ?
Couldn’t that (or something of that kind) explain these apparently random dips in luminosity ?

UFOsMOTHER
Member
UFOsMOTHER
October 17, 2015 4:40 PM

O.K. We have no solid proof what is causing this but i think there is a Black Hole between the Star and Earth that is warping the true effect..

robst247
Member
October 17, 2015 6:51 PM

Would it be fair to say that this is the most important ‘smoke signal’ we’ve ever received from the cosmos? I just can’t think of a natural explanation for this phenomenon. Not even highly chaotic motions of a large number of huge protoplanets fits the bill, because there have been long periods without any dips in brightness, and there is no evidence of periodicy.

sangos
Member
sangos
October 18, 2015 1:50 AM

Absolutely. SETI should call it the ‘OMG’ signal. Btw dunno if its official but read the star has a shorter more easy rename WTF-001. F = flux wink

Senwaxa
Member
October 18, 2015 9:32 PM
Not enough is being said about the ‘brightness that seems to go up and down roughly every 20 days for weeks, then disappears completely.’ (Slate) Mercury orbits our Sun every 88 days. KIC 8462852’s Star is 1.5 times the size as our Sun. A 20-day orbit around 8462852 I would assume would be very fast and very hot. Hot enough for smelting I assume? It seems like if you were building a mega-structure or adding new panels to a mega-huge solar power array, you’d probably want the smelting plant somewhat close to what you’re building. Then every 20-days the smelting facility ‘flings’ out the mega-huge smelted piece towards it’s intended destination. At the same time some fairly common… Read more »
prospector
Member
prospector
October 20, 2015 7:57 PM
First off i would like to say how interesting and well written this article is as well as the comments that followed. Looking at the problem, it seems there are innumerable conclusions that can be drawn based on the evidence i have seen, and that evidence also raises a lot of questions. One of these being the light dips of the star, are they completely static throughout the duration of the anomaly or is there a path to it? If so can this path be traced in repetition, suggesting a orbit of some kind or form. On the subject of a Dyson sphere seems odd to me that any kind of advanced intelligent life would use a solid… Read more »
Bo Zo
Member
Bo Zo
October 20, 2015 9:18 PM

I’ll bet a beverage that we humans work out a plausible solution very soon, and a solid solution very soon after. It may (or may not) require more observational data. It may be much sooner (it may have happened yesterday), but I bet, conservatively, this will be in the bag by 2017.

Don’t forget, one of the intelligent species in the Milky Way is us. We were clever enough to invent WISE and Keppler, and to make note of the KIC anomaly. Now we want to know what it is.

grabsjoker
Member
grabsjoker
October 23, 2015 10:24 AM

Curious about something. If a civilization is advanced enough to create solar panels in space, presumably the next/ultimate step would be to make a proper dyson sphere. Given this, how long in that civilizations existence would the solar panels be around before being replaced by a sphere? 10 years? 100? 1000? What are the chances that we’d detect a civilization in this intermediate stage?

robst247
Member
October 23, 2015 10:39 AM
Interestingly, I was just reading this article on http://www.EarthSky.org about a new discovery of a small planetary object that seems to be breaking apart around a white dwarf: http://earthsky.org/space/astronomers-find-dead-star-destroy-a-planet This paragraph seems particularly relevant in the context of KIC-tel.no.: “A research team found an unusual, but vaguely familiar pattern in the data. While there was a prominent dip in brightness occurring every 4.5 hours, blocking up to 40 percent of the white dwarf’s light, the transit signal of the tiny planet did not exhibit the typical symmetric U-shaped pattern. It showed an asymmetric elongated slope pattern that would indicate the presence of a comet-like tail. Together these features indicated a ring of dusty debris circling the white dwarf,… Read more »
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