Hey guys, i made a thread a couple of weeks ago about how to derive equations for exoplanet data, and so far i´ve managed to derive an equation for the radial velocity as:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]V_{rad}=K[cos(\theta + \omega) + ecos(\theta + \omega)[/tex]

Which i'm guessing would be the function to be plotting against the radial velocity data i get, although i have not been able to derive how [tex]\theta[/tex] is a function of time yet. But that's not what i'm trying to derive at right now. Right now i'm having troubles finding a equation to give me the mass of the planet from the given data i get from the plot. I'm guessing i get [tex]\omega, e, P,a[/tex] and the mass of the sun is already known, where e is eccentricity, P the period and a the semi-major axis.

This is pretty much where i'm stuck, i thought today i'd found a way. Since [tex]K=\frac{2\Piasin(i)}{P(1-e^2)^{1/2}}[/tex] and a can be written as [tex]a=\frac{L^2}{(1-e^2)GMm^2}[/tex], then i saw a formula (must admit that i have not trie deriving this formula yet, i just wanted to see if i could use it to get writ of L since that's a crossproduct and i wanted something with known constants insted of L), [tex]L=\frac{2\Pia^2(1-e^2)^{1/2}mM}{P(m+M)}[/tex], so i was thrilled and figured i could now write a as [tex]a=\frac{4 \pi^2 a^4M)}{GP^2(M+m)}[/tex] and could substitute that into my K equation to get [tex]K=\frac{8 \pi^3 a^4Msin(i)}{P^3G(M+m)^2(1-e^2)^{1/2}}[/tex] From which i could simply isolate m and get a nice equation for my mass, but this doesn't seem to give right results (if i just take data from exoplanets.org and put it in it does not agree with what they get), although checking the units i do seem to end up with Kg's.

Sorry for asking questions about this again and starting a new thread, but this isn't going too smoothly for me :yuck:

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# More exoplanet equation problems :/

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