# Drake's Equation Question Set: what fraction of stars form planets?

This is the second question in a series estimating input parameters for Drake's equation, inspired by a recent paper, on the Fermi paradox.

The first question in the series, with more explanation, is here

The model in question uses probability distributions over the following parameters:

• $R_∗$ log-uniform from 1 to 100.
• $f_p$ log-uniform from 0.1 to 1.
• $n_e$ log-uniform from 0.1 to 1.
• $f_l$ log-normal rate, $1 − e^{−λVt}$ (giving $f_l$ mean 0.5 and median - 0.63).
• $f_i$ log-uniform from 0.001 to 1.
• $f_c$ log-uniform from 0.01 to 1.
• $L$ log-uniform from 100 to 10,000,000,000.

In this case we will be addressing the second parameter in Drake's Equation, $f_p$. It is the fraction of the stars in the first parameter with planets. Predictors should use the sliders to best approximate their estimate and uncertainties in this parameter.

All evidence seems to indicate this will resolve very close to 1 (100%), though it is worth considering how this may be mistaken.

For example, if we consider a much broader set of suitable stars in the 1st parameter then it maybe the fraction is lower as stars less likely to possess planets are included.

We'll consider each planet to belong to a single star, so a binary star system with one planet, for example, corresponds to 50% of stars having planets.

The resolution to this question will be the scientific consensus 100 years from now, regardless of any remaining uncertainty.

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