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2

Some time back, I made a jupyter notebook (in French, but the names of the satellites are similar enough) that compares the angular diameter of Jupiter as seen from its moons to the angular diameter of our own Moon seen from Earth. This way, you can get an idea of how big Jupiter would look in comparison to a more familiar sight. For instance, if the Moon (...


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Science fiction writers and scientists have imagined the possibility of exomoons orbiting giant exoplanets in other star systems being habitable. And htere have been scientific articles discussing the possible limits of exomoon habitabilty. In my answer to this question: https://worldbuilding.stackexchange.com/questions/176513/what-do-i-bear-in-mind-...


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You can simply startup Stellarium and have a look yourself. Choose any locations you are interested in. The Galilean satellites of Jupiter are inside the default list of locations. The attached image shows Jupiter as viewed from Io at the given time, Europa is the bright object to the right; with -9 mag it is considerably brighter than Venus when viewed ...


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The sun is the nearest star to Alpha Centauri (unless you count Proxima Centauri, which is really part of the same system). There is a very small and dim pair of brown dwarfs, called Luhman 16 that are closer, at about 3.6 light years from Alpha Centauri. Brown dwarfs are not true stars, but they do glow from their own heat. They were only discovered in ...


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For small angles the Laurent series of $1/ \tan(x)$ about zero begins: $$\frac{1}{\tan(x)} = \frac{1}{x} - \frac{x}{3} - ... = \frac{1}{x} \left( 1 - \frac{x^2}{3} -...\right)$$ so for small $\alpha$ the approximation $1/ \alpha$ will be high by about the fraction $\alpha^2/3$. This means that the error in the distance determined by parallax will be only ...


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For angles of magnitude 1/50 arcsecond (of the order $10^{-7}$, the difference between $\tan\alpha$ and $\alpha$ is truly negligible (if alpha is in radians) and only a matter of a choice of units if you don't. It is quite correct to say: distance (in AU) = 1/angle (in radians) to get the distance from the angle in radians. Using parsecs a means that we ...


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