The discussion revolves around determining the orbital radius of extrasolar planets, with participants expressing confusion about the methods to find this radius. The subject area includes concepts from orbital mechanics and gravitational forces.
The conversation is ongoing, with some participants seeking specific formulas while others provide insights into the relationships between forces acting on the planet. There is a recognition of the complexity involved in determining the necessary parameters.
Participants highlight the difficulty in obtaining certain measurements, particularly the mass of the star, which complicates the calculation of the orbital radius. The original poster expresses a need for clarity in understanding the underlying formulas.
Delphi51 said:We have a formula relating the period of the orbit to its radius. It is easy to observe the period, so the radius can then be calculated. The longer answer is that the formula has the mass of the star in it and that mass is not easy to observe. I think some guessing is involved but I don't really know. Stars are very interesting and a lot is known about how they work, so perhaps there is a way to guess the mass fairly well from observations of the star's characteristics.