KIC 8462852 (dipping again in March 2018)

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In summary: KIC 8462852 is a star that has been exhibiting strange dips in brightness, which some are suggesting could be due to an alien presence.
  • #281
Vanadium 50 said:
Why?
Same reason you see Polaris as the north star.
 
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  • #282
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").
 
  • #283
stefan r said:
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?
 
  • #284
Vanadium 50 said:
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.
 
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  • #285
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?
 
  • #286
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?
 
  • #287
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.
 
  • #288
JMz said:
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.
 
  • #289
Vanadium 50 said:
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.
 
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  • #290
stefan r said:
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.
 
  • #291
Vanadium 50 said:
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)
axial-tilt.jpg


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

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  • #292
JMz said:
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.
 
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  • #293
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.
 
  • #294
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
 
  • #295
mfb said:
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.
 
  • #296
Vanadium 50 said:
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.
 
  • #297
Birrabenzina said:
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.
 
<h2>1. What is KIC 8462852 and why is it significant?</h2><p>KIC 8462852, also known as Tabby's Star, is a mysterious and unique star located in the constellation Cygnus. It gained attention in 2015 when it was observed to have unusual and irregular dips in its brightness. These dips cannot be explained by any known natural phenomenon and have sparked speculation of extraterrestrial activity.</p><h2>2. What caused the sudden dip in March 2018?</h2><p>The exact cause of the dip in March 2018 is still unknown. Some scientists believe it could be due to a swarm of comets passing in front of the star, while others suggest it could be caused by a large object passing between the star and Earth. However, more research and data analysis is needed to determine the true cause.</p><h2>3. Has KIC 8462852 shown any other strange behavior?</h2><p>Yes, Tabby's Star has shown irregular dips in brightness multiple times since its discovery in 2015. These dips have varied in duration and intensity, leading to further confusion and speculation about the cause. However, no definitive explanation has been found yet.</p><h2>4. What are some theories about the unusual dips in KIC 8462852's brightness?</h2><p>Some theories suggest that the dips could be caused by a massive alien structure known as a Dyson sphere, which would block the star's light as it orbits. Others propose the possibility of a large planet or debris field passing in front of the star. However, these are all just theories and have not been confirmed.</p><h2>5. How are scientists studying KIC 8462852 and its unusual behavior?</h2><p>Scientists are using various methods to study Tabby's Star, including ground-based telescopes and space-based telescopes like the Kepler Space Telescope. They are also analyzing data and looking for patterns in the star's behavior to try and understand the cause of the dips in brightness. Additionally, scientists are searching for any signs of radio signals or other evidence of extraterrestrial activity in the star's vicinity.</p>

1. What is KIC 8462852 and why is it significant?

KIC 8462852, also known as Tabby's Star, is a mysterious and unique star located in the constellation Cygnus. It gained attention in 2015 when it was observed to have unusual and irregular dips in its brightness. These dips cannot be explained by any known natural phenomenon and have sparked speculation of extraterrestrial activity.

2. What caused the sudden dip in March 2018?

The exact cause of the dip in March 2018 is still unknown. Some scientists believe it could be due to a swarm of comets passing in front of the star, while others suggest it could be caused by a large object passing between the star and Earth. However, more research and data analysis is needed to determine the true cause.

3. Has KIC 8462852 shown any other strange behavior?

Yes, Tabby's Star has shown irregular dips in brightness multiple times since its discovery in 2015. These dips have varied in duration and intensity, leading to further confusion and speculation about the cause. However, no definitive explanation has been found yet.

4. What are some theories about the unusual dips in KIC 8462852's brightness?

Some theories suggest that the dips could be caused by a massive alien structure known as a Dyson sphere, which would block the star's light as it orbits. Others propose the possibility of a large planet or debris field passing in front of the star. However, these are all just theories and have not been confirmed.

5. How are scientists studying KIC 8462852 and its unusual behavior?

Scientists are using various methods to study Tabby's Star, including ground-based telescopes and space-based telescopes like the Kepler Space Telescope. They are also analyzing data and looking for patterns in the star's behavior to try and understand the cause of the dips in brightness. Additionally, scientists are searching for any signs of radio signals or other evidence of extraterrestrial activity in the star's vicinity.

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