A KIC 8462852 (dipping again in March 2018)

[Drakkith]

I think you are a bit too harsh. Extraterrestrial explanation is a "serious" contenter (it _is_ possible, it's not insane or totally stupid).

I disagree that a "serious" contender is one that simply isn't outright impossible.

To those reading this thread take note of the tone of my posts and the tone of this one: personal, emotional.

And also logical. Your support for your assertions so far has been "we can't rule it out therefor we should take it seriously". That's not how one does science. The "serious" contenders are the ones that we think are most probable based on our prior experience and current knowledge. That's where you start and that's where you begin to rule out the various possibilities.

This person has also done what a few other replies have done and characterize my assertion that the extraterrestrial hypothesis be a "serious" contender. I've only ever said it should be a contender and taken seriously.

Those are equivalent in many people's view.

This reply makes my point better than I've been able that there's a societal bias whenever the subject of extraterrestrials (in any context) comes up. It's not this person or anyone else's fault since it's been pushed in our culture for over fifty years. The impulse to shrug off, ridicule, dismiss, and in the case of the scientific community looked down on with derision. We have generations that have been marinated in the stereotypes of people taking aliens as serious as being crackpots, eccentric and unhinged. While it's pretty easy to understand where this bias came from it has no business in the scientific community.

Nonsense. We have hundreds of years of experience in explaining unknown phenomena and so far exactly zero of them have been attributed to extraterrestrials. On a list of possible explanations for the peculiar light curves of KIC 8462852, extraterrestrial aliens are so far down that they fall well outside the "serious" or "likely" sections. I'd put it in the "neat, but extremely unlikely" section at best.

 

[Drakkith]

All of astronomy has "extraterrestrial" explanations except maybe some lunar and near Earth orbits. Perhaps you intend to mean biological, sentient, or artificial?

Sentient extraterrestrial life.

 

[stefan r]

If there is a Dyson sphere somewhere we can recognize it as made by aliens. No one doubts that.
But if there is no Dyson sphere, it doesn't mean there are no aliens. And that direction is the problem.

I doubt that. And agree that there is a problem.

I can write about Dyson spheres because I do not have a telescope (at least not one worth mentioning). I do not have a lab. There is no budget for future projects that may be compromised by weird publicity. My employment would not be effected even if I was diagnosed insane or senile.

If you see evidence for a Dyson sphere the right thing to do is categorize it as a Vega type star. Then you should get more/better data. It would be a disservice to the public, your students, and/or your coworkers if you lose access. In the current social/political environment the right thing to do is not report what you believe you saw. Just document hard data so that someone in a future and less hostile environment can access your data and put together long term trends.

--
Note that KIC8462852 does not look like a Vega type star.

 

[Pdgenoa]

How dare you recall it a planet...

I get the joke but I want to point out that a "dwarf" planet is still a planet the same as a human with dwarfism is still a human

*additionally: suck it NDT!

 

[jerromyjon]

I get the joke but I want to point out that a "dwarf" planet is still a planet

R.I.P. formally planet known as Pluto in tribute to the artist formerly known as Prince...

 

[Drakkith]

I get the joke but I want to point out that a "dwarf" planet is still a planet the same as a human with dwarfism is still a human

No it isn't. Per the IAU:

The IAU therefore resolves that planets and other bodies, except satellites, in our Solar System be defined into three distinct categories in the following way:
(1) A planet¹ is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d)is not a satellite.

Planets and dwarf planets are in two distinct categories. A dwarf planet is not a subtype of planet, despite what the name leads you to believe.

 

[mfb]

The star keeps dipping. A fourth dip started, at more than 1.5% and potentially still getting deeper.

From here

Independent observations

 

[smartalek86]

I'm just wondering, what is our resolving power at those distances, i.e. what can we eliminate...
also is there any point in point an x-ray telescope at it?

 

[mfb]

Hubble has an angular resolution of ~0.05 arcseconds, at 1300 light years this corresponds to 20 AU. VLT in interferometry mode can reach 0.004 arcseconds, corresponding to 1.6 AU. This does not mean you could see anything a few AU away from the star, however: It is roughly a billion times brighter than possible planets.
ELT will get a 10⁸ contrast for 0.03 arcseconds separation (~12 AU), if there is something bright far away from the star that could be visible. 2024+The fourth dip is over, peak dimming was a bit more than 2%.

 

[smartalek86]

can something like this https://www1.lehigh.edu/news/‘styrofoam’-planet-may-help-solve-mystery-giant-planets
be eliminated?

 

[Drakkith]

can something like this https://www1.lehigh.edu/news/‘styrofoam’-planet-may-help-solve-mystery-giant-planets
be eliminated?

Probably. I don't think the interval between dips is short enough or regular enough to be explained by such a planet, which, according to the article, is a type of "hot Jupiter". These planets general have an orbital period of a few days and they cause predictable dips in the light curve instead of erratic dips.

 

[mfb]

There is some periodic structure, but nothing a single planet could do. The dips observed by Kepler are way too deep for any sort of planet, and they also last too long and have a structure too complex for a planet.

Multiple planets with ring systems are possible.

 

[stefan r]

can something like this https://www1.lehigh.edu/news/‘styrofoam’-planet-may-help-solve-mystery-giant-planets
be eliminated?

Alien fifth graders making a mega-structure does not have any evidence that I can find. Would be a sub category in "aliens made it". A megastructure made out of polystyrene seams as plausible as aluminum, steel, shell (silica, calcium carbonate), or spider silk. Any would still be a remarkable find.

A polystyrene foam with density 0.05 g/cm² and Earth radius would collapse into high density polystyrene. High temperatures and pressure would then modify the chemistry. I believe a Jupiter mass planet made out of an equal parts mix of hydrogen and carbon would be denser than Jupiter. Adding more mass does not increase the volume. Brown dwarfs are close to Jupiter's volume. A hollow shell with 20X Jupiter's surface might not collapse. It is hard to explain how that would come to exist.

Astronomers have found low density planets with radii larger than Jupiter. The article referred to KELT 11b. Hot Jupiter planets orbit close to stars and are hot. The high temperatures help explain the low densities. A 760 day orbit would not add much more heat than Earth gets from the sun (per square meter).

The thing around KIC 8468252 would have to have 1/5th KIC 8468252's cross section in order to block enough light. A hot surface radiates infrared radiation. When a hot Jupiter passes in front of a star the infrared should drop less than the measured visible light. When a hot Jupiter passes behind a star the measured infrared drops but visible light will measure normal for that star.

As a hot Jupiter sphere revolves the visible light should gradually change as the light reflecting off the surface waxes and wanes. Like full moon to new moon phase cycles. The reflected light also eclipses when the planet passes behind the star. The object around KIC 8468252 could be extremely dark and/or not a sphere.

 

[newjerseyrunner]

Alien fifth graders making a mega-structure does not have any evidence that I can find. Would be a sub category in "aliens made it". A megastructure made out of polystyrene seams as plausible as aluminum, steel, shell (silica, calcium carbonate), or spider silk. Any would still be a remarkable find.

A polystyrene foam with density 0.05 g/cm² and Earth radius would collapse into high density polystyrene. High temperatures and pressure would then modify the chemistry. I believe a Jupiter mass planet made out of an equal parts mix of hydrogen and carbon would be denser than Jupiter. Adding more mass does not increase the volume. Brown dwarfs are close to Jupiter's volume. A hollow shell with 20X Jupiter's surface might not collapse. It is hard to explain how that would come to exist.

Astronomers have found low density planets with radii larger than Jupiter. The article referred to KELT 11b. Hot Jupiter planets orbit close to stars and are hot. The high temperatures help explain the low densities. A 760 day orbit would not add much more heat than Earth gets from the sun (per square meter).

The thing around KIC 8468252 would have to have 1/5th KIC 8468252's cross section in order to block enough light. A hot surface radiates infrared radiation. When a hot Jupiter passes in front of a star the infrared should drop less than the measured visible light. When a hot Jupiter passes behind a star the measured infrared drops but visible light will measure normal for that star.

As a hot Jupiter sphere revolves the visible light should gradually change as the light reflecting off the surface waxes and wanes. Like full moon to new moon phase cycles. The reflected light also eclipses when the planet passes behind the star. The object around KIC 8468252 could be extremely dark and/or not a sphere.

Hot Jupiter's also make the star itself wobble which there is no evidence for there. Whatever is passing in front of the star seems to have negligible mass.

 

[stefan r]

Hot Jupiter's also make the star itself wobble which there is no evidence for there. Whatever is passing in front of the star seems to have negligible mass.

This article claims they only measured within 400 m/s radial velocity. In their model they have a planet with orbital period ~12 years and trojans making the 2 year events. They calculate total mass less than 130 Jupiters.

The ESO has HARPS installed on a telescope and they claim 1 m/s velocity measurements. They built one for the northern hemisphere but measurements of KIC 8462852 did not come up in a google search. I would not call 1/4th Jupiter mass "negligible".

 

[Simon Peach]

A conglomeration of dark matter?

 

[Drakkith]

A conglomeration of dark matter?

Unlikely. The dark matter model that best fits the available evidence points towards dark matter which doesn't conglomerate.

 

[stefan r]

A conglomeration of dark matter?

"Dark matter" is a single concept. Does not mean the same thing as "matter which is dark". In order to be "dark matter" it does not emit, adsorb, or reflect light.

 

[Elroch]

NASA have concluded the explanation is most likely fine dust. The difference in dimming between ultraviolet and infrared makes larger solid objects unlikely explanations.

 

[Pdgenoa]

Yeah, the dust "proof" settles everything.

Except the gradual, century long dimming.
Or the periodic brightening of the star.
Or why the dust hasn't been pulled into the star if it's in the system.
Or how dust that's far away but in between us and it could have such dramatic occlusion.

So I'm just SURE this hypothesis won't end up like the past 27 hypotheses.
Yeah.

 

[mfb]

Do you have a reference that dust cannot explain these?

 

[stefan r]

Spitzer measured infrared at 4.5μm . If a black body at 370 degrees C it should radiate 4.5μm radiation. Is there a way to distinguish between a filter that blocks only UV and a filter that blocks some of everything and also emits lower frequencies? The temperature on Mercury's equator rises over 400C.

 

[mfb]

During January and February, the star is too close to the Sun for observations. Measurements resumed two weeks ago, and since March 16 the star shows another dip. Currently 4% below the baseline, the deepest dip seen since the end of Kepler observations.

Image source and more information: tldr: DIPPING!

 

[mfb]

A second dip just a week later. - probably ~5% but with infrequent measurements around the dip time.

 

[rootone]

Could it be that the visible star has two or more very large but non-luminous brown dwarf objects associated in that system?

 

[stefan r]

A second dip just a week later. - probably ~5% but with infrequent measurements around the dip time.

View attachment 222859

How are they calculating the error?
How are they determining normal?

Could it be that the visible star has two or more very large but non-luminous brown dwarf objects associated in that system?

A brown dwarf has close to the same radius as Jupiter. A 4% dip requires more like 7 Jupiter sized objects.

Brown dwarf stars close to KIC8462852 would show some Doppler shift. There could be lots of cold brown dwarfs in many places.

 

[jerromyjon]

Could it be that the visible star has two or more very large but non-luminous brown dwarf objects associated in that system?

It doesn't come in gradually, like a body transiting. It dims suddenly. And randomly.?

 

[mfb]

How are they calculating the error?
How are they determining normal?

I don't know, see the linked web page for details. Kepler just normalized to the flux outside the dips, but the star seems to have a non-constant apparent magnitude outside the dips as well.

It doesn't come in gradually, like a body transiting. It dims suddenly. And randomly.?

Compared to planet transits the dips have quite long slopes. Jupiter moves by 1 diameter in its orbit every 1.5 hours, but the dips start and end over 1-3 days.

 

[JMz]

So the object in orbit is very close, has too little mass to create much of a wobble in the host star, but covers a surface area much larger than Jupiter?

Giant ring huh? Obviously a Halo joke, but it gave me an idea.

If you tipped Saturn on it's side like Uranus and put it close to the sun, would it block enough light? It'd be quite variable since sometimes you'd see the rings head on and it'd block only as much light as the planet disc itself, but sometimes you'd see the rings from "above" and it'd have a shadow of hundreds of thousands of miles.

If the planet is that close to the star, it's moons are probably quite active and could easily create a ring I wo

Saturn's rings have a radius of 120,000 km but are only partially opaque, whereas the Sun has a radius > 400,000 km. So at most, the rings would absorb about 8% if they were opaque and properly oriented wrt the star and properly oriented wrt us.

Note that there is no direction in which a star could see Saturn's rings oriented that way wrt to the Sun.

BTW, if Saturn were so oriented, then every time it passed between the Sun and that star, it would present the same face. That star would not see only the planet sometimes, and planet+rings other times.

 

[Vanadium 50]

BTW, if Saturn were so oriented, then every time it passed between the Sun and that star, it would present the same face.

Why?

 

[stefan r]

Why?

Same reason you see Polaris as the north star.

 

[JMz]

A refinement: The face it presented would change its orientation only very slightly over a few years. (Remember, we have only a few years of observations of this star.)

Because of conservation of angular momentum: the same reason that the Earth's polar axis changes only slightly over a few years, completing a full circuit in 26,000 years ("precession of the equinoxes").

 

[Vanadium 50]

Same reason you see Polaris as the north star.

That didn't clarify anything. Why would a ringed system necessarily show the same face to us every orbit?

 

[stefan r]

That didn't clarify anything. Why would a ringed system necessarily show the same face to us every orbit?

sorry,

If Earth had an ring over the equator then astronomers on Polaris would always see the ring face on. The moon (and earth) would always be near quarter full. The polar ice cap would face Polaris year round but would stop reflecting in the winter when it got dark.

The pole star can be any angle. Uranus has Eta Ophiuchi as a pole star.

 

[Vanadium 50]

Right, but suppose your aliens lived on Regulus rather than Polaris. They would see Earth or Saturn - or better still, Uranus - transit the sun - why is the ring orientation necessarily constant?

 

[JMz]

Because, just like the planet, the rings have angular momentum, and angular momentum is conserved unless acted on by an external torque. What would you propose for the source of that torque?

 

[JMz]

To clarify (I hope): The rings would always appear face-on, whether or not they were between the Sun and that star (though they wouldn't be visible when they weren't occulting the Sun). They don't change orientation relative to the star as they orbit the Sun, just as the Earth's axis doesn't change orientation relative to Polaris or any other star over the course of a year.

 

[stefan r]

To clarify (I hope): The rings would always appear face-on, whether or not they were between the Sun and that star (though they wouldn't be visible when they weren't occulting the Sun). They don't change orientation relative to the star as they orbit the Sun, just as the Earth's axis doesn't change orientation relative to Polaris or any other star over the course of a year.

When Galileo first looked at Saturn he noticed that Saturn had ears. If the rings had been face on it would have looked like another sphere. Rings viewed off of axis might be better for explaining strange light curves.

 

[mfb]

Right, but suppose your aliens lived on Regulus rather than Polaris. They would see Earth or Saturn - or better still, Uranus - transit the sun - why is the ring orientation necessarily constant?

It is not*, but the stellar occultation always happens at the same point in the orbit. And at the same point of the orbit the orientation of a ring system would be constant over short timescales. If precession would be relevant over tens of orbits then the ring system should be extremely short-living.

*edit: I was wrong. It is, see two posts below, the same point in the orbit is not even necessary.

 

[JMz]

When Galileo first looked at Saturn he noticed that Saturn had ears. If the rings had been face on it would have looked like another sphere. Rings viewed off of axis might be better for explaining strange light curves.

The more tilted the rings are, the less they will occult. This hypothesis is already aiming for substantially more coverage than even Saturn's unusually large and dense rings can provide, even if they were oriented like Uranus's.

 

[DaveC426913]

That didn't clarify anything. Why would a ringed system necessarily show the same face to us every orbit?

Am I missing something here? Or are you? (I question myself because I know you're super smart.)

From a distant viewpoint a planet's axial tilt and ring system will always look the same, no matter where it is in its orbit, and no matter what year you look at it.

Planets are gyroscopes!

Saturn's axis and rings are likewise fixed relative to the stellar background. From outside our solar system, it too will always be seen at the same angle.

Like so: (but with rings)

It is only because we are in the solar system that we see Saturn from different angles, and therefore different orientations of its rings.

 

[mfb]

The more tilted the rings are, the less they will occult. This hypothesis is already aiming for substantially more coverage than even Saturn's unusually large and dense rings can provide, even if they were oriented like Uranus's.

We don't know if Saturn's rings are unusually large. J1407b probably has a ring system with 200 times the diameter of Saturn's rings. Easily large enough to obscure the whole star, leading to a massive (>90%) dip in brightness.
The duration and frequency of the dips in KIC 8462852 rule out a similar explanation there.

 

[Vanadium 50]

I now see what you're saying, and my problem is I wrote what I wrote, not what I meant. What I was imaging was a set of irregular rings, darker/thicker in spots, partially obscured by the planet. This would give you a kind of irregular periodicty.

 

[Birrabenzina]

This star is pretty interesting.
Has someone any link to some paper which analyzes this star in detail? Maybe it's a double system with a type Y or T brown dwarf

 

[JMz]

We don't know if Saturn's rings are unusually large. J1407b probably has a ring system with 200 times the diameter of Saturn's rings. Easily large enough to obscure the whole star, leading to a massive (>90%) dip in brightness.
The duration and frequency of the dips in KIC 8462852 rule out a similar explanation there.

A good point. For rings in the Solar System, big planets have rings -- but they're all insignificant (in blocking sunlight for distant observers) except for Saturn. My unstated hypothesis was that large, dense ring systems are very rare, and that the few we know of are known just because of a very strong observational selection effect.

But of course, even if that's true, this star could be one of those few -- after all, it's obviously a rare beast, one way or another.

 

[JMz]

I now see what you're saying, and my problem is I wrote what I wrote, not what I meant. What I was imaging was a set of irregular rings, darker/thicker in spots, partially obscured by the planet. This would give you a kind of irregular periodicty.

Got it -- sort of like Neptune's. My impression is that such rings would not be both large/dense and incomplete, except for a brief interval soon after formation. (And this star is not newly born.) But whether or not that's typical, we are dealing with an atypical system: All explanations so far are either poor fits to the data or improbable scenarios.

 

[stefan r]

This star is pretty interesting.
Has someone any link to some paper which analyzes this star in detail? Maybe it's a double system with a type Y or T brown dwarf

Here is the "official" web site. It has links to peer reviewed papers and also an ongoing blog with current data. The wikipedia entry is fairly good.

A brown dwarf would not eclipse 20% of a type-F main sequence star. It might block 1% or 2%. The light curve of a planet or brown dwarf transiting a star has a flat bottom. The flat bottom light curve is there if you toss a basketball in front of a movie projector. Moths in front of street lights also have flat bottom light curves. You could get a pointy light curve by throwing a basketball partially in front of a street light. The object has to be big.