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 16 2016, 06:39 PM
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#2
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
Okay, I've decided to download the full archive of Harvard Observatory observations of this object. I went to the DASCH Lightcurve Access page, and entered the object's coordinates: 20 06 15.457 +44 27 24.61 and got a text file that I converted to a spreadsheet file (which I tried to upload to this post, but it was not allowed).
I extracted the magnitude measurements with an RMS equal to or less than 0.2 (1265 data points) and created a chart with a second-order polynomial trend line: There is a definite decline of about 0.2 magnitude (the trend line appears to underestimate this), but it also appears relatively flat from 1890 to 1953, and when observations resume in the late 1960s, the average brightness appears to be well below the earlier values and steadily declining. |
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Jan 25 2016, 05:50 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
The use of archival data to study the brightness variations lead me to another thought: How many other stars have shown this (or another) sort of hitherto-unexplained dimming? If we had data like this on KIC 8462852, and Kepler was only observing 1/400th of the sky, it is seemingly almost certain that more stars like this exist… depending on the definition of "like this."
Here are the basic observed facts about KIC 8462852, to summarize: 1) Progressive dimming over several decades, which may be occurring in steps rather than smoothly. 2) Sudden and reversible dimming on rare occasions during the Kepler observations. The baseline during this time was quite constant, and the dips occurred during a tiny fraction of the Kepler observations. The duration of these events was similar to planetary occultation, but the magnitude was anomalously large, the timing between them was irregular, and the shape of them was unlike any planet or star transit. 3) The IR spectra indicates that there is not a large amount of warm dust in the system. The reason why the comet explanation seems to fit (2) and (3) is because comets spend almost all of their time far from the star, and so could absorb a bit of warmth in a small time and radiate it over a long time; the radiation must be re-radiated, but could happen at a longer wavelength than warm dust would. To assimilate all of these into one exogenous explanation, all I can come up with is: KIC 8462852 is surrounded by a massive amount of material that is occulting it, to a considerable degree, all the time, but the individual particles are predominantly in highly elliptical orbits. Ongoing catastrophic events are generating progressively more occulting material, so the fraction of the star's light that is being blocked is increasing from an already-high degree to an even higher degree. Alternately, something internal to the star may be occurring, and therein I have no insight to offer. As with the exogenous explanation, any endogenous cause must certainly be something rare and therefore unusual. It's a puzzler. It's like astronomy as written by Agatha Christie. |
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Jan 25 2016, 08:26 PM
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#4
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
... To assimilate all of these into one exogenous explanation, all I can come up with is: KIC 8462852 is surrounded by a massive amount of material that is occulting it, to a considerable degree, all the time, but the individual particles are predominantly in highly elliptical orbits. Ongoing catastrophic events are generating progressively more occulting material, so the fraction of the star's light that is being blocked is increasing from an already-high degree to an even higher degree. ... It's a puzzler. It's like astronomy as written by Agatha Christie. Well, just because a star is middle aged and main sequence, doesn't mean things with the planets can't get, er, interesting.... QUOTE (On the Dynamical Stability of the Solar System) Konstantin Batygin, Gregory Laughlin (Submitted on 11 Apr 2008) A long-term numerical integration of the classical Newtonian approximation to the planetary orbital motions of the full Solar System (sun + 8 planets), spanning 20 Gyr, was performed. ... The experiments yielded one evolution in which Mercury falls onto the Sun at ~1.261Gyr from now, and another in which Mercury and Venus collide in ~862Myr. In the latter solution, as a result of Mercury's unstable behavior, Mars was ejected from the Solar System at ~822Myr. http://arxiv.org/abs/0804.1946 Apply that sort of scenario to Tabby's star, two rocky planets collide, a third is ejected (likely scattering comets) and there ought to be plenty of material around to create long term and periodic dimming of the star. |
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