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Wikipedia claims that Saturn's rings may be as old as Saturn itself; NASA says that they could be only a few hundred million years old. The 4.something-billion-years-old fits in with one of the two theories of the rings' formation - that Saturn swept up material from the protoplanetary disk. The date makes sense, because there's no way the disk would last ...

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Planet "candidates" are Kepler Objects of Interest (KOIs)that have a transit-like light curve and have passed a number of observational tests. They are candidates, because although they do show a transit in the light curve of the star in question, there is no independent confirmation of a planetary mass. One problem to overcome is that of "false ...

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Here is a plot I generated in 5 minutes at the site exoplanets.org To construct this I took planets discovered by the transit method and which had a $M \sin i$ measured using radial velocities. I divided the $M \sin i$ by the sine of the measured inclination angle (this is required to avoid using masses that have been estimated using an assumed mass-radius ...

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With regard to gas giants, there is no mass limit. Conceptually, what's the difference between a star plus a Jupiter-class gas giant versus a star plus a brown dwarf companion versus a star plus a red dwarf versus a binary pair of stars of more or less the same mass? This is a spectrum with no clear boundary, no clear limits. With regard to density, there's ...

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Arguably, "rogue planets" have already been discovered by direct imaging. Giant planets when first formed are big and hot. They radiate their own light, mostly in the infrared. So young isolated planets can be seen directly. There have been various claims in the literature that objects as small as a few Jupiter masses have been identified in young star ...

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