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Old 08-25-2017, 04:06 PM   #1
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Default Exocomets around a star

One of the possible explanations for the anomalous behavior of the famous Tabby Star (KIC 8462852) is the presence of giant clouds of comets around it. But for the moment it has not been possible to confirm this hypothesis, nor that the variations of brightness are due to alien structures. Obviously detecting a comet around another star is not as fascinating as discovering extraterrestrial megastructures, but it is an impressive achievement. And while we wait for news of the Tabby Star it seems that at last we can exclaim eureka! With respect to the extrasolar comets, because a team of researchers with Saul Rappaport at the head has announced the discovery -provisional, as it usually happens- of the first exocometas (not sets of kites or Kuiper belts in other stars, but solitary exocomets. ).

During the primary mission of Kepler, between 2009 and 2013, the star underwent six transits, that is, something went ahead six times. The deepest transits block between 0.12% and 0.15% of the light of the star, but since they are not equispaced in time and their depth is not equal it can not be a planet.

The six transits of KIC 3542116 (Rappaport et al.).
And if it is not a planet, what is it? Rappaport and his colleagues interpret the strange light curves of these transits as comets with long tails that pass through the star's disc. The shapes of the light curves coincide with the theoretical models of exocometas, so we would be before six different comets. To explain the observed transits the tail of each kite must have a minimum mass of 1013 kg of dust. The speed of each kite around the star would be between 35 and 50 km / s for deeper transits (implying periods ranging from a few days to 300 days) and between 75 and 90 km / s for the kites of the Transits less striking. Comets with a mass greater than 3 1014 kg could explain the transits, which goes into the feasible considering that this is more or less the mass of the comet Halley. The cometary hypothesis is reinforced because Rappaport and his people have found another star, KIC 11084727, with a similar transit to the six of KIC 3542116, so we would be talking about seven exocometas in total.
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Old 08-25-2017, 06:58 PM   #2
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0.12-0.15% makes sense for comets... >20% dips with KIC 8462852 makes zero sense for comets, IMO. Plus there's that whole long-term dimming thing with KIC 8462852 too.
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