A KIC 8462852 (dipping again in March 2018)

[craigi]

There doesn't seem to be a thread about this, but it's very popular in the news today. I thought it'd be good to have a place to discuss it here.

 

[Borg]

KIC 8462852.

 

[DaveC426913]

Some really intriguing light curves here. Read the article for some explanation.

http://www.slate.com/blogs/bad_astr...ge_dips_in_brightness_are_a_bit_baffling.html

Look at the smooth curve lower left. That has got to be a single body transit. Multiple bodies couldn't make such a smooth curve. Yet that body results in a 15% drop in the light curve!
And it's cold, so not a companion star.

I don't see how exo-comet fragments can explain this.

Black dwarf?

 

[inuk2600]

Can we be sure that the obstructing bodies are local to KIC 8462852's system? Are they known to be in orbit around KIC 8462852?
Perhaps they appear so large because they may be a group of stray asteroids which are much closer to us than we think, and not in fact in orbit.

 

[DaveC426913]

That's been considered, yes.
The problem is, the farther from the star the more incredibly unlikely that they would line up and stayed lined up.

 

[inuk2600]

That's been considered, yes.
The problem is, the farther from the star the more incredibly unlikely that they would line up and stayed lined up.

Some really intriguing light curves here. Read the article for some explanation.

http://www.slate.com/blogs/bad_astr...ge_dips_in_brightness_are_a_bit_baffling.html

Look at the smooth curve lower left. That has got to be a single body transit. Multiple bodies couldn't make such a smooth curve. Yet that body results in a 15% drop in the light curve!
And it's cold, so not a companion star.

I don't see how exo-comet fragments can explain this.

Black dwarf?

The universe isn't old enough for black dwarfs, they would still be brown dwarfs radiating mad infrared at least.

 

[nsaspook]

KIC 8462852 – Where’s the flux?

http://arxiv.org/pdf/1509.03622v1.pdf

 

[Czcibor]

KIC 8462852.

Shouldn't a part of Dyson Sphere be a bit closer thus obscure its star in more regular and frequent pattern?
Those aliens really do a shoddy work and park their panels on wrong orbits. Next time, when they arrive to make crop circles someone would have to explain that to them ;)

EDIT: Media are delighted because right now no explanation is really convincing, but this "alien did it" part is also not so good.

Personally I'd opt for some collision stuff, planets with rings and selection bias.

 

[Vanadium 50]

It's not out of the question that the star itself is variable. It doesn't fit any known categories, but in 1994 neither did Gamma Doradus. (Now it's in the category of "Gamma Doradus variables".)

 

[nsaspook]

...
EDIT: Media are delighted because right now no explanation is really convincing, but this "alien did it" part is also not so good.

This is another case where IMO it takes 'Two to Tango'. Someone with book on Aliens sees the KIC 8462852 paper, makes a juicy line and calls a media friend to push it. The media person calls the author of the original paper and pushes them for an Alien connection that they probably laugh at and say sure that's, possible.

Next stop, Dyson Sphere and Time Ships.

 

[Artribution]

Shouldn't a part of Dyson Sphere be a bit closer thus obscure its star in more regular and frequent pattern?
Those aliens really do a shoddy work and park their panels on wrong orbits.

Aliens: Thank you, Earth ape. We'd love to have a look at one of your designs.

 

[TurtleMeister]

Some really intriguing light curves here. Read the article for some explanation.

http://www.slate.com/blogs/bad_astr...ge_dips_in_brightness_are_a_bit_baffling.html

Look at the smooth curve lower left. That has got to be a single body transit. Multiple bodies couldn't make such a smooth curve. Yet that body results in a 15% drop in the light curve!
And it's cold, so not a companion star.

I don't see how exo-comet fragments can explain this.

Black dwarf?

That lightcurve looks very similar (except for it's magnitude) to the one produced by KIC12557548, which is discussed in this Scientific American blog from May 2012. They also give a possible explanation.

 

[Vanadium 50]

That lightcurve looks very similar (except for it's magnitude) to the one produced by KIC12557548, which is discussed in this Scientific American blog from May 2012.

Same group too.

 

[DaveC426913]

The universe isn't old enough for black dwarfs, they would still be brown dwarfs radiating mad infrared at least.

I know. Looking for plausible explanations.

 

[DaveC426913]

Once we blow through all the alien jokes, maybe we can talk serious.

 

[inuk2600]

I know. Looking for plausible explanations.

It was new to me, I had to wiki it. Any new ideas bubbling up out there?

 

[Andy Resnick]

Here it is, captured @ 85/2, 1 hr integration time, 300% magnification:

 

[Dotini]

It was new to me, I had to wiki it. Any new ideas bubbling up out there?

Here's a new idea from 1957:

 

[DaveC426913]

Here it is, captured @ 85/2, 1 hr integration time, 300% magnification:

I KNEW it!
Look at that giant ring. Aliens, plain as day!

 

[newjerseyrunner]

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?

I KNEW it!
Look at that giant ring. Aliens, plain as day!

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

 

[DaveC426913]

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

No, look at the picture! Post 17. Oh never mind, the joke's lost.

Besides, Larry Niven's Ringworld was around decades before today's video games... :P

 

[Drakkith]

Besides, Larry Niven's Ringworld was around decades before today's video games... :P

Nonsense! The world didn't exist before video games!

 

[ZenShadow]

We'll know more when SETI tunes in ... and, oh let's point ole Hubble at 'er and see what's up.

 

[sophiecentaur]

Perhaps they appear so large because they may be a group of stray asteroids which are much closer to us than we think, and not in fact in orbit.

Would it be naive of me to suggest that, if that were the explanation, they would be regularly blocking off the light from many other sources? That would take an almost trivial test to verify the idea or otherwise.

 

[Bandersnatch]

Before jumping to conclusions and speculation, I'd suggest people first read the paper linked by nsaspook in post #7. Section 4.4.1 provides constraints on the size and orbit of the debris.
To be frank, I don't even see where the whole Dyson sphere (or swarm or ring) idea came from, other than an off-kilter comment by one of the scientists. It doesn't fit the constraints at all.

 

[inuk2600]

Would it be naive of me to suggest that, if that were the explanation, they would be regularly blocking off the light from many other sources? That would take an almost trivial test to verify the idea or otherwise.

If we had the capabilitity to apply Kepler level analysis to whole sky then yes I think we would see such a thing happening. Are you suggesting the possibility of a stray but dense swarm of asteroids (ok how about comets) in interstellar space is absurd?

 

[inuk2600]

Before jumping to conclusions and speculation, I'd suggest people first read the paper linked by nsaspook in post #7. Section 4.4.1 provides constraints on the size and orbit of the debris.
To be frank, I don't even see where the whole Dyson sphere (or swarm or ring) idea came from, other than an off-kilter comment by one of the scientists. It doesn't fit the constraints at all.

The author specifies constraints based on the assumption of a circular orbit.

 

[Bandersnatch]

The author specifies constraints based on the assumption of a circular orbit.

Follow to section 4.4.5.

 

[inuk2600]

Follow to section 4.4.5.

Still the author is assuming the objects are in orbit. However unlikely the relative speeds may be, can we confidently rule out the possibility that the objects are in interstellar space?
What other crazy ideas are we considering here? Orbital comets that massively occult a star that's bigger than the sun and an alien Dyson sphere.

 

[Dotini]

What other crazy ideas are we considering here? Orbital comets that massively occult a star that's bigger than the sun and an alien Dyson sphere.

I prefer Hoyle's black cloud to an alien Dyson sphere.

 

[Bandersnatch]

Still the author is assuming the objects are in orbit. However unlikely the relative speeds may be, can we confidently rule out the possibility that the objects are in interstellar space?
What other crazy ideas are we considering here? Orbital comets that massively occult a star that's bigger than the sun and an alien Dyson sphere.

The problem with an interstellar cloud of debris is that you need it to maintain sufficient spread for the required occultation, without collapsing under its own gravity to form a more compact object.

 

[inuk2600]

The problem with an interstellar cloud of debris is that you need it to maintain sufficient spread for the required occultation, without collapsing under its own gravity to form a more compact object.

Is it really a problem or a failure of imagination?

 

[Ernest S Walton]

Still the author is assuming the objects are in orbit. However unlikely the relative speeds may be, can we confidently rule out the possibility that the objects are in interstellar space?

The authors clearly rule it out, saying "...clumps that are too distant move too slowly across the stellar disk to explain the observed duration regardless of their size; e.g., a 3-day duration dip cannot arise from a clump beyond 15 AU." And they go on to say "... the middle solid line and a depth of = 20% therefore decreases the outer limit on the clump locations mentioned above to closer to 8 AU."

 

[inuk2600]

The authors clearly rule it out, saying "...clumps that are too distant move too slowly across the stellar disk to explain the observed duration regardless of their size; e.g., a 3-day duration dip cannot arise from a clump beyond 15 AU." And they go on to say "... the middle solid line and a depth of = 20% therefore decreases the outer limit on the clump locations mentioned above to closer to 8 AU."

This is true if the objects are in orbit and local to the system. Remember these constraints assume the objects are in orbit.

 

[sophiecentaur]

Remember these constraints assume the objects are in orbit

Do you have any other suggestions?

 

[inuk2600]

Do you have any other suggestions?

That's all I got.

 

[Lanniakea]

Can someone point me towards the mathematics behind estimating the size of an object from the dip in light curve? I read somewhere (I can't remember for the life of me where) that if the object blocking this star was the size of Jupiter, the dip in flux would have been less than 1%. This is a periodic dip of 15-22%, which is insane if correct. Can anyone verify these estimations?

 

[Bandersnatch]

Can someone point me towards the mathematics behind estimating the size of an object from the dip in light curve? I read somewhere (I can't remember for the life of me where) that if the object blocking this star was the size of Jupiter, the dip in flux would have been less than 1%. This is a periodic dip of 15-22%, which is insane if correct. Can anyone verify these estimations?

Since the star and occulting object is so far away, you can assume the light rays coming from the disc of the star to be parallel. The percentage of luminosity dip caused by the occulting object is then just the percentage of the disc of the star that is covered by the object. In other words, the dip is proportional to the ratio of the cross-sectional areas of the object and the star.

You know how Jupiter is roughly 10 times smaller than the Sun by radius? Compare the area of a circle with radius 1/10 R (Jupiter) with the area of a circle with radius R (Sun):
$\frac{A_{planet}}{A_{star}}$
$\frac{\pi (0.1R_{Sun})^2}{\pi R_{Sun}^2}=0.01$
Or 1%. The star being the subject of this discussion is larger than the Sun, so a Jupiter-sized planet would occult less than the 1%. To calculate how much less, do the same calculation as above, only with the radius of the star equal to 1.58 R.

 

[Lanniakea]

Since the star and occulting object is so far away, you can assume the light rays coming from the disc of the star to be parallel. The percentage of luminosity dip caused by the occulting object is then just the percentage of the disc of the star that is covered by the object. In other words, the dip is proportional to the ratio of the cross-sectional areas of the object and the star.

You know how Jupiter is roughly 10 times smaller than the Sun by radius? Compare the area of a circle with radius 1/10 R (Jupiter) with the area of a circle with radius R (Sun):
$\frac{A_{planet}}{A_{star}}$
$\frac{\pi (0.1R_{Sun})^2}{\pi R_{Sun}^2}=0.01$
Or 1%. The star being the subject of this discussion is larger than the Sun, so a Jupiter-sized planet would occult less than the 1%. To calculate how much less, do the same calculation as above, only with the radius of the star equal to 1.58 R.

Thank you! My only question is, how much would the distance from the star contribute? For example let's say Jupiter was orbiting this star at 2 AU away, would it not theoretically block more light from our perspective if it were say 8 AU away? It is established that this object does orbit the star (or else it's an astronomical coincidence) with a period of about 750 days. If this local distance effect is negligible and if I'm doing the maffs correctly, then here are some results:

If the object occulting this star were a sphere with the radius of Jupiter, it would block 0.4% of the incoming light.
If the occulting object is a sphere that blocks between 15% and 22% of the incoming light (as observed), its radius would have to be between 61% and 74% of our sun's radius.
For perspective, TrES-4b is the fourth biggest planet discovered according to wikipedia, and it's radius is about 1.8 that of Jupiter, which gives us very roughly 18% solar radii.

What the hell is that?

 

[newjerseyrunner]

@Lanniakea that's why it's more likely a fairly small object (in terms of mass.) If it were huge, we'd also see the star getting pulled around by it's gravity.

Dense objects like planets have small radii, defuse objects can be much much larger. If you were looking at our solar system, the widest object isn't Jupiter, it's Saturn. A comet approaching the sun's coma also can be significantly wider than Jupiter.

I wonder if a large moon or plutoid being pushed inward could create the affect. What would happen if a fairly large stray object (rogue planet) passed close enough to Jupiter to pull one of it's moon away. Would it act like a short term comet? I imagine if a comet 50 miles across can create a coma thousands of miles across, an icy object 500 miles across could make a mind bogglingly huge coma.

 

[Lanniakea]

@Lanniakea that's why it's more likely a fairly small object (in terms of mass.) If it were huge, we'd also see the star getting pulled around by it's gravity.

Dense objects like planets have small radii, defuse objects can be much much larger. If you were looking at our solar system, the widest object isn't Jupiter, it's Saturn. A comet approaching the sun's coma also can be significantly wider than Jupiter.

I wonder if a large moon or plutoid being pushed inward could create the affect. What would happen if a fairly large stray object (rogue planet) passed close enough to Jupiter to pull one of it's moon away. Would it act like a short term comet? I imagine if a comet 50 miles across can create a coma thousands of miles across, an icy object 500 miles across could make a mind bogglingly huge coma.

The object has a period of about 750 days and the first time it passed it created a 15% dip, and then 750 days later a 22% dip + many smaller dips around this time. I'm by no means an astronomer, but what kind of diffuse object or even pack of comets blocks 61-74% of the sun's radius worth of light at a periodic interval? In the paper they say a broken up exocomet is the most likely scenario of all they considered, and I with my completely unprofessional opinion agree, a broken up/smeared out object seems to be by far the most likely explanation, but 61-74% solar radius? Wow

EDIT: The 4th biggest planet I mentioned is basically a big ball of gas that is speculated to have a huge tail and hilariously low density. I don't see what density has to do with anything here?

 

[Bandersnatch]

My only question is, how much would the distance from the star contribute? For example let's say Jupiter was orbiting this star at 2 AU away, would it not theoretically block more light from our perspective if it were say 8 AU away?

The distance doesn't contribute, because the thing you're looking at is so far away.
If you were to draw light rays coming to your eye from the edges of an object, you'd get something like this:

If you place an object between the source and the observer, how much light reaches the observer will depend on the proportion of the distance between the two lines that the object obscures.

Now imagine the distance d increases to an absurdly large value as compared to the size of the object being observed (here, ~1500 light-years vs 1.58 Sun radii). The angle alpha becomes very small, and the lines of light rays become indistinguishable from parallel on the scale of a stellar system. So whether the object is 1 AU or 1 ly from the star, the distance between the lines of light rays is practically unchanged, and the same amount of light gets blocked.

 

[DaveC426913]

In the paper they say a broken up exocomet is the most likely scenario of all they considered, and I with my completely unprofessional opinion agree, a broken up/smeared out object seems to be by far the most likely explanation, but 61-74% solar radius? Wow

EDIT: The 4th biggest planet I mentioned is basically a big ball of gas that is speculated to have a huge tail and hilariously low density. I don't see what density has to do with anything here?

Well, equivalent to. As a cloud of smaller objects, it won't be and object of that radius.

But even at that, what sized comet would be required to create a debris field that can eclipse 15-22% of a star's light?

Here's a math question for someone:
What is the smallest mass of a cloud that could eclipse 22% of this sun? We'd have to assume some typical shape to the cloud. (If it were a flat disk, seen face-on, like a wall then you'd need far smaller mass, but that's not a plausible shape) And we have no idea how much larger than the star's disc the cloud is. Also donlt know what size particles are.

Let's start with a basic ideal shape. Let's say the cloud is entirely contained within the sun's disc, and let's say the cloud it is spherical. What is the minimum mass of the cloud to occlude 22% of the sun's disc?

 

[Bandersnatch]

Let's start with a basic ideal shape. Let's say the cloud is entirely contained within the sun's disc, and let's say the cloud it is spherical. What is the minimum mass of the cloud to occlude 22% of the sun's disc?

Minimum?
Then you need only one particle in a whole cloud per line of sight. That is, you can compress the spherical cloud of particles into a solid disc, with thickness equal to the size of the particles (assuming they're uniform).

The radius of the disc to obscure 22% of 1.58 solar radii star is about 0.75 solar radii. That gives an area of about 10e18 m^2.
Let's say the size of the dust particles is about 1mm across, and that they are composed of water ice. That gives mass in the ballpark of 10e18 kg, or 1/1000th of Ceres' mass.

 

[DaveC426913]

Minimum?
Then you need only one particle in a whole cloud per line of sight. That is, you can compress the spherical cloud of particles into a solid disc, with thickness equal to the size of the particles (assuming they're uniform).

You stopped reading halfway though, didn't you?

We'd have to assume some typical shape to the cloud. (If it were a flat disk, seen face-on, like a wall then you'd need far smaller mass, but that's not a plausible shape)

 

[Bandersnatch]

You stopped reading halfway though, didn't you?

I kinda did , but then I read again and realized that editing is unnecessary as the answer is still correct - a solid disc is the minimum mass approximation of an obscuring sphere of dust. As was said, you only need one particle in your line of sight, so take that 1-particle-thick disc of dust, and spread it around in 3d - it doesn't matter what gaps are there between particles, as long as you never have two particles in the same line of sight, and you don't spread them beyond the visible disc of the star.

The point being, if you spread it well enough, even a medium-size asteroid-worth of dust is enough to account for the luminosity dip.

Or to put it another way, if you start with a fully-compacted object of mass m, unbind it, and start spreading it around in a spherical fashion, at some point you will have spread it to the extent where the separation between particles comprising the cloud is sufficiently large to avoid more than one particle per line of sight. That's the maximum the mass m can block of the background object, and it's the same as if you just made a solid disc of the same mass.

 

[Lanniakea]

The distance doesn't contribute, because the thing you're looking at is so far away.
If you were to draw light rays coming to your eye from the edges of an object, you'd get something like this:
View attachment 90551
If you place an object between the source and the observer, how much light reaches the observer will depend on the proportion of the distance between the two lines that the object obscures.

Now imagine the distance d increases to an absurdly large value as compared to the size of the object being observed (here, ~1500 light-years vs 1.58 Sun radii). The angle alpha becomes very small, and the lines of light rays become indistinguishable from parallel on the scale of a stellar system. So whether the object is 1 AU or 1 ly from the star, the distance between the lines of light rays is practically unchanged, and the same amount of light gets blocked.

Thank you so much for this, when you explain it like that it becomes almost obvious!

They talk about about a nearby star within about 1000AU passing by that could of in theory disturbed the star's oort cloud in a way that sent a massive cloud of fragments that somehow ended up in an orbit in our line of sight. And this is as far as I know the most logical explanation. But that has to be one helluva cloud to block so much light... Is it reasonable for it to stay coalesced like this (at such a scale) and not give off a detectable IR signal?

Also I haven't seen much light curves like this before, but can dusty/particulate masses create such sharp and well defined dips during transit?

Ahh why did Kepler have to not work in April, this is like an itch I can't scratch. x)
Maybe aliens are decommissioning a very large ice skating rink?

 

[DaveC426913]

I kinda did , but then I read again and realized that editing is unnecessary as the answer is still correct

You're still missing the point. We have to assume a plausible shape to the dust cloud. Flat discs (whose plane is tangential to the star) are impossible, and no such shape will give us any first order approximation of the mass required. Reject it.

Let's assume a spherical cloud. So a sphere of diameter 1.58 Sols. (This too is not a likely shape, but it'll be a lot closer.)

 

[newjerseyrunner]

You're still missing the point. We have to assume a plausible shape to the dust cloud. Flat discs (whose plane is tangential to the star) are impossible, and no such shape will give us any first order approximation of the mass required. Reject it.

Let's assume a spherical cloud. So a sphere of diameter 1.58 Sols. (This too is not a likely shape, but it'll be a lot closer.)

Ignorant question: what is a sol? A solar diameter?

I have a question: how does a big planet migrate inward? I know that many of the first exoplanets discovered were gas giants orbiting very closely to their star, to close to have formed there. Do they migrate in slowly or does it happen in a few well timed gravitational tugs? If gas giant with icy moons migrates inwards, wouldn't all of those moon start to sublimate all at once and produce a monstrous cloud / ring system? If the planet started out on it's side like Uranus, wouldn't it create a flat disc perpendicular to the planet's orbit?

 

[DaveC426913]

Ignorant question: what is a sol? A solar diameter?

Simpler. A Sol is simply our sun.
So a sphere of diameter 1.58 Sols is a sphere of diameter 1.58x our sun's.

I have a question: how does a big planet migrate inward? I know that many of the first exoplanets discovered were gas giants orbiting very closely to their star, to close to have formed there. Do they migrate in slowly or does it happen in a few well timed gravitational tugs? If gas giant with icy moons migrates inwards, wouldn't all of those moon start to sublimate all at once and produce a monstrous cloud / ring system? If the planet started out on it's side like Uranus, wouldn't it create a flat disc perpendicular to the planet's orbit?

Pretty sure migration happens over astronomical times scales, i.e. tens of millions of years.

No lunar orbit can be maintained at any near distance from the star. (eg. Mercury and Venus have no moons) .
If the planet and moons migrated inward, the moons would form a ring around the star, in the same plane and orbit as the planet.