Why is combining data from the Transit method (size) and RV method (mass) crucial for planetary characterization?

Answer

It allows for the calculation of the planet's density

When the size derived from the Transit method is combined with the minimum mass derived from the RV method, astronomers can calculate the planet's density, which provides insight into its composition (rocky or gaseous).

Why is combining data from the Transit method (size) and RV method (mass) crucial for planetary characterization?
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