User:Dhrm77/exoplanets

Introduction
In the last few years, after the discovery of the first hundreds of exoplanets, there has been a few lists of most earth-like exoplanets, but these lists were somewhat random lacking a way to quantify the similarities.

Note that this is NOT an article, and will most likely never be. To obtain a similarity index, an arbitrary choice has been made concerning how much weight each parameter has in its calculation. Therefore it is highly subjective.

Similarity index
Here is a table where a similarity index was calculated based on the Mass, Radius, Flux, Temperature, and orbital period of each planet compared to earth. When that information wasn't available, a best estimate was used.

This table isn't by any mean complete. New discoveries and added information should lead to an updated version of it from time to time.

Ideally, the composition of the atmosphere of each planet would be included in the calculation of the index, but that information is currently scare or non-existent. And in order to obtain a list of significant size, it is not included. Obviously, when that information becomes available, the ranking of each planet is likely to drastically change.

Here is how the similarity index was calculated:

First a weight for each parameter is chosen: This is somewhat arbitrary. Mass and Radius are somewhere redundant since they are both related to gravity. Flux and temperature are somewhat related but more important then gravity. The orbital period is somewhat not that important, so a low value was chosen. Then the absolute value of the log of the ratio of each parameter divided by that parameter for Earth is calculated. Then each value is multiplied by its corresponding weight. Then, let's take S as the sum of all weights. The index is calculated by dividing S by [S plus the sum of all the weighted values].