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Solar System comets
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Title: The Tidal Downsizing hypothesis for planet formation and the composition of Solar System comets
Authors: Sergei Nayakshin, Seung-Hoon Cha, John Bridges (Leicester)

Comets are believed to be born in the outer Solar System where the temperature is assumed to have never exceeded T ~ 100 K. Surprisingly, observations and samples of cometary dust particles returned to Earth showed that they are in fact made of a mix of ices, as expected, but also of materials forged at high-temperatures (T ~ 1500 K). We propose a radically new view regarding the origin of the high-temperature processed materials in comets, based on the recent "Tidal Downsizing" (TD) hypothesis for planet formation. In the latter, the outer proto-planetary disc is gravitationally unstable and forms massive giant planet embryos (GEs). These hot (T ~ hundreds to 2000 K) and dense regions, immersed in the background cold and low density disc, are eventually disrupted. We propose that both planets and the high-T materials in comets are synthesised inside the GEs. Disruption of GEs separates planets and small solids as the latter are "frozen-in" into gas and are peeled off together with it. These small solids are then mixed with the ambient cold disc containing ices before being incorporated into comets. Several predictions of this picture may be testable with future observations of the Solar System and exoplanets.

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RE: Comet
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Scientists from the Max Planck Institute for Solar System Research identify the active regions on the surface of comets

Studying comets can be quite dangerous - especially from close up. Because the tiny particles of dust emitted into space from the so-called active regions on a comet's surface can damage space probes. Scientists from the Max Planck Institute for Solar System Research in Germany have now developed a computer model that can locate these regions using only the information available from Earth. The new method could help calculate a safe flight route for ESA's space probe Rosetta, which is scheduled to arrive at the comet Churyumov-Gerasimenko in 2014. (Astronomy & Astrophysics, 512, A60, 2010)
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Comets
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Comets, the Solar System's Most Spectacular Nomads

An interactive web site provides an overview of comets - including details on their anatomy and information on comets that have been visited by spacecraft.
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RE: Comet
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The Taurid meteor shower that rains down on the Earth every autumn is the visible remains of a comet that once broke up in Earth's orbit. To ancient civilisations these fiery streaks of light in the sky were nothing less than Gods - bringers of life or harbingers of doom. But what of the comet itself - where did it come from and what happened to it? This programme explores both the current deep-space missions that are revealing the origin and nature of comets, and historical myths that surrounded these beautiful celestial phenomena.


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Life in the inner galaxy would be bombarded by comets

We're lucky Earth resides in the Milky Way's suburbs. Intense comet bombardment near the galaxy's centre may make it tough for life to gain a foothold there.
Earth and the other planets of our solar system suffer occasional impacts when comets are disturbed from their orbits around the sun by the gravity of nearby stars and gas clouds.
The effect is stronger closer to the galaxy's centre, where stars and gas clouds are more tightly packed.

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Twelve Sungrazing Comets

Orbital elements:
Comet T q e Peri. Node Incl. C
CK09B080 2009 Jan. 21.629 0.00478 1.0 84.680 5.210 143.226 X
CK09B090 2009 Jan. 29.798 0.00668 1.0 58.277 328.572 132.966 X
CK09B110 2009 Jan. 31.403 0.00512 1.0 83.745 4.910 143.000 X
CK09C030 2009 Feb. 5.650 0.00477 1.0 82.563 3.894 144.553 X
CK09C040 2009 Feb. 9.118 0.00644 1.0 77.941 1.043 143.688 X
CK09D020 2009 Feb. 19.768 0.00621 1.0 75.465 0.224 143.452 X
CK09D030 2009 Feb. 19.838 0.00496 1.0 87.042 8.678 143.647 X
CK09D040 2009 Feb. 23.436 0.00533 1.0 83.614 4.877 144.469 X
CK09D050 2009 Feb. 24.413 0.00354 1.0 85.460 3.565 143.305 X
CK09D070 2009 Feb. 27.554 0.00537 1.0 79.112 358.962 144.051 X
CK09E020 2009 Mar. 1.868 0.00292 1.0 97.276 14.240 142.356 X
CK09E040 2009 Mar. 11.078 0.00582 1.0 78.481 359.671 143.954 X

MPEC 2009 - X45


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Thirteen Sungrazing Comets

Orbital elements:
Comet T q e Peri. Node Incl. C
CK08B020 2008 Jan. 28.413 0.00481 1.0 76.962 357.388 144.125 X
CK08K040 2008 May 23.842 0.00460 1.0 82.786 3.725 144.537 X
CK08N020 2008 July 4.529 0.00472 1.0 78.214 358.188 143.974 X
CK08N080 2008 July 9.224 0.00523 1.0 83.663 4.645 144.501 X
CK08P030 2008 Aug. 7.372 0.00477 1.0 78.266 358.420 143.992 X
CK08R100 2008 Sept. 9.267 0.00453 1.0 79.283 358.621 143.946 X
CK08X110 2008 Dec. 6.121 0.00729 1.0 86.162 7.558 143.870 X
CK08X120 2008 Dec. 9.969 0.00530 1.0 85.147 6.661 144.172 X
CK08Y060 2008 Dec. 22.160 0.00509 1.0 85.921 6.946 144.055 X
CK08Y070 2008 Dec. 22.219 0.00516 1.0 85.010 6.093 144.269 X
CK08Y100 2008 Dec. 23.067 0.00527 1.0 80.933 1.081 143.742 X
CK08Y130 2008 Dec. 28.506 0.00490 1.0 91.617 13.517 142.297 X
CK08Y150 2008 Dec. 30.452 0.00473 1.0 90.236 11.664 141.454 X

MPEC 2009 - X38


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Eleven Sungrazing Comets

Orbital elements:
Comet T q e Peri. Node Incl. C
CK07C030 2007 Feb. 2.468 0.00390 1.0 84.490 4.106 143.634 X
CK07C060 2007 Feb. 7.228 0.00553 1.0 63.735 338.361 139.192 X
CK07C130 2007 Feb. 16.156 0.00360 1.0 91.124 12.212 144.157 X
CK07F030 2007 Mar. 28.273 0.00790 1.0 60.216 336.363 138.539 X
CK07M040 2007 June 26.368 0.00712 1.0 84.005 5.060 144.513 X
CK07N070 2007 July 14.543 0.00487 1.0 85.353 7.043 144.837 X
CK07S050 2007 Sept. 28.108 0.00489 1.0 85.958 7.718 144.698 X
CK07V040 2007 Nov. 3.815 0.00459 1.0 77.944 357.745 144.044 X
CK07V110 2007 Nov. 12.192 0.00459 1.0 83.111 4.126 144.356 X
CK07X100 2007 Dec. 14.450 0.00464 1.0 77.190 357.003 144.096 X
CK07Y050 2007 Dec. 24.065 0.00969 1.0 74.831 354.376 143.845 X

MPEC 2009 - X37


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Light Curves of Comets
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Title: "Atlas of Secular Light Curves of Comets"
Authors: Ignacio Ferrin

In this work we have compiled 37,692 observations of 27 periodic and non-periodic comets to create the secular light curves (SLCs), using 2 plots per comet. The data has been reduced homogeneously. Our overriding goal is to learn the properties of the ensemble of comets. More than 30 parameters are listed, of which over ~20 are new and measured from the plots. We define two ages for a comet using activity as a proxy, the photometric age P-AGE, and the time-age, T-AGE. It is shown that these two parameters are robust, implying that the input data can have significant errors but P-AGE and T-AGE come out with small errors. This is due to their mathematical definition. It is shown that P-AGE classifies comets by shape of their light curve. The value of this Atlas is twofold: The SLCs not only show what we know, but also show what we do not know, thus pointing the way to meaningful observations. Besides their scientific value, these plots are useful for planning observations. The SLCs have not been modeled, and there is no cometary light curve standard model as there is for some variable stars (i.e. eclipsing binaries). Comets are classified by age and size. In this way it is found that 29P/Schwassmann-Wachmann 1 is a baby goliath comet, while C/1983 J1 Sugano-Saigusa-Fujikawa is a middle age dwarf. There are new classes of comets based on their photometric properties. The secular light curves presented in this Atlas exhibit complexity beyond current understanding.

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RE: Comet
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Four new comets were discovered on archive images taken by the STEREO-A satellite (instruments HI1-A and COR2-A) and by the STEREO-B satellite (instrument COR2-B).
All the comets belong to the Kreutz orbital group.

C/2009 A8 (STEREO) Alan Watson
C/2009 A9 (STEREO) Rob Matson
C/2009 A10 (STEREO) Alan Watson
C/2009 O1 (STEREO) Michal Kusiak


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