Quote:
Originally Posted by Sporally
And here are some data about the sizes of each planet in Jupiter masses:
Gliese 876c: 0.56
HD 92788b: 3.86
HD 16175b: 4.5
HD 20367b: 1.07
HD 142415b: 1.62
HD 142b: 1
HD 108874b: 1.36 (that solar system also features a Jupiter sized planet 2.5 times as far away from the sun - maybe helping in the defence of a possible moon with life)
HD 150706b: 1
HD 190228b: 4.99
So from the data above i would say when we get those planets with a size like:
HD 92788b
HD 16175b
HD 190228b
... as possible planets with a Earth-sized moon around them.
Is the calculation of how big a moon typically would be if you for instance double the size of the planet? I mean, taking a planet with 2 Jupiter-masses, would that mean that it is likely we would get a 2 Ganymedes-masses moon around that planet or isn't it a linear calculation?
BTW: Would it be easier or harder to find a Earth-sized moon around a planet than a Earth-sized planet around a star if we would search just as many of each type? I'm not talking about in which situation there are most Earth-sized planets/moons, but what future telescopes like Kepler would find easier finding.
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If the moons and the planet condense from the same proto-Jovian disk then there has to be some relationship between the masses, but other factors could have a substantial effect. Someone here referenced a paper that concluded that the satellites of a planet that condense with it should be about 1/10000th (?) the mass of the planet. <calculates mentally> the regular moons of Jupiter would add up to about 1/5000th the mass of Jupiter, and Saturn similarly, so that sounds about right. By that token an Earth mass satellite would be unlikely around anything smaller than a brown dwarf. A Mars sized body though wouldn't surprise around a big Jovian.
As to which are easier to find, I dunno. But there's
talk of finding exomoons around transiting planets.
I estimated the bolometric luminosities by applying the
Stefan–Boltzmann law to the temperatures (and radii) on exoplanets.eu. The approximation probably gets ratty for cool M dwarfs. Another way would be to have looked up the spectral types in a bolometric correction table. That was too tedious. Note that at least one prominent website devoted to the habitability of exoplanets uses uncorrected visual luminosities resulting in incorrect conclusions (such as Gl581c being cooler than Earth).