KIC 8462852 Observations |
KIC 8462852 Observations |
Oct 15 2015, 04:45 PM
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#1
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Kepler found one very, very strange case:
http://www.theatlantic.com/science/archive...-galaxy/410023/ In a nutshell, while Kepler was observing it, the star (larger and brighter than the Sun) exhibited four dimming events that took place at irregular intervals, blocked a lot more light than a Jupiter-sized planet would block, and had a "shape" that varied in all four cases and did not resemble a planet. This case is attracting some wild speculation… in fact, it is seemingly certain that something wild must be going on; it's just a matter of which wild scenario is the correct one. If I had to throw my hat in the ring, I'd guess that a distant collision and breakup has placed big swarms of matter into a very long-period orbit. But there's no hypothesis that's been offered that doesn't seem problematic. |
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Jan 25 2016, 10:04 PM
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#2
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Junior Member Group: Members Posts: 68 Joined: 27-March 15 Member No.: 7426 |
If I recall correctly, the Kepler Space telescope found no periodicities in the dips in light from this star. We're assuming, it seems, that the plane in which any planets, or their shattered debris would travel, aligns with the star from our point of view.
Even if two planets had collided and destroyed themselves, we might have expected other planets, or even just one, to be found, mightn't we? If there was a complete absence of planets around this star, these collisional scenarios would seem to be unworkable. |
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Jan 26 2016, 12:52 AM
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#3
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
If I recall correctly, the Kepler Space telescope found no periodicities in the dips in light from this star. We're assuming, it seems, that the plane in which any planets, or their shattered debris would travel, aligns with the star from our point of view. The did see something with a 750 day period. For reference, mars' orbit is 687 days, so assuming the "something big" is in orbit, that would be, eh, roughly around the inner edge of our asteroid belt. Even if two planets had collided and destroyed themselves, we might have expected other planets, or even just one, to be found, mightn't we? If there was a complete absence of planets around this star, these collisional scenarios would seem to be unworkable. Brilliant question! Complex answer. Rephrased- "If Kepler was looking at our own solar system from Tabby's planet, how many of our planets would it see transit?" If all the planets around a sun have the same angle, and the same 'phase' (argument of perihelion?) then yes. In practice, no. Here are our planet's orbital tilts relative to earth. Mercury 7.01° Venus 3.39° Earth 0 Mars 1.85° Jupiter 1.31° Saturn 2.49° Uranus 0.77° Neptune 1.77° https://en.wikipedia.org/wiki/Orbital_inclination It's a difference of a few degrees, but at several million KM away from the sun, a small angle leads to a big distance above or below the orbital plane. And, each tilt is going to be oriented in a different direction- imagine looking down at the solar system as if it were a compass. So, Mercury's tilt is above the plane towards North and below towards South, but Venus' might be above at East and below at West. Another way to think about it- why are solar eclipses special? Even though we have a (relatively) large moon, that is close to the same plane as the sun, it's actually quite rare for the orbit of the moon to line up with the orbit of the sun. |
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Jan 26 2016, 09:20 AM
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#4
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
The did see something with a 750 day period. No. The first dip, which by itself resembled one planetary transit, was seen at mission day ~792 and then a very strange series of several dips took place roughly from days 1510 to 1570. Nothing in the later series of dips is obviously a repeat of the first observed dimming event. The paper has a section discussing the possibility of the second event being related to the first, with a ~750 day period; in the discussion, that possibility is called "problematic." Follow-up observations showing a lack of IR excess further discredit that possibility. Without a third observation, the inference that two light curve dips indicate one specific "something" is doubtful even in a less strange case. An observer elsewhere could see Venus and Earth both transit the Sun, but wouldn't know whether those two transits were caused by one planet or two planets until a third transit was seen. Whatever was seen between days ~1510-1570 was seen only once, and what was seen at day ~792 was not obviously seen even one more time, much less two more times. |
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