Radio waves can indeed pass through planets and stars, although their behavior may be influenced by the properties of the objects they encounter.
When radio waves encounter planets, they can pass through the planet's atmosphere and continue their propagation. However, the atmosphere can affect the radio waves by causing absorption, scattering, or reflection, depending on the composition and density of the planet's atmosphere. For instance, certain wavelengths of radio waves can be absorbed by molecules in an atmosphere, limiting their transmission through it. Additionally, the atmosphere may scatter or reflect the radio waves, altering their direction or intensity.
As for stars, radio waves can also travel through the outer layers of a star, including the photosphere and the chromosphere. However, once the waves encounter the dense and turbulent regions of a star's interior, they can be absorbed or scattered due to the high densities and temperatures present. The absorption and scattering of radio waves within stellar interiors make it difficult to observe or receive radio signals from the core or deeper regions of a star.
Nevertheless, radio astronomy allows scientists to study celestial objects, including planets and stars, by detecting and analyzing the radio waves they emit. By using specialized radio telescopes and techniques, astronomers can gather valuable information about these objects and their properties, despite the potential interactions that may occur when radio waves encounter them.