def R_roche(rho_pl, rho_sat):
    """
    Compute roche radius of a planet as a function of the planet's radius
    
    Parameters:
    ----------
    rho_pl: Array-like;
        density of the planet
        
    rho_sat: Array-like;
        density of the satellite
          
    Returns
    -------
    
    R_roche: Array-like;
        Roche radius of the planet
    """    
    
    return  2.44*((1.0*rho_pl)/rho_sat)**(1/3.)