tähtipinta

Tähtipinta is a Finnish term that translates to "star surface" or "star face." It is most commonly used in the context of astronomy to describe the apparent visible surface of a star. This is not a physically distinct boundary but rather the region from which most of the light we observe emanates.

The visible surface of a star, or its photosphere, is the layer where the star becomes opaque to radiation. Above the photosphere, the star's atmosphere is transparent, allowing photons to escape freely. Below it, the stellar interior is opaque, trapping radiation. Therefore, the photosphere is effectively the "surface" we see when we look at a star.

The temperature and composition of the photosphere determine the star's spectral type and its visual appearance. Features like sunspots on our Sun are also observed on the photosphere. The concept of a "star surface" is therefore crucial for understanding stellar properties, stellar evolution, and how we classify and study stars in the universe. While the term "tähtipinta" might be used colloquially, in precise astronomical contexts, "photosphere" is the more scientifically accurate term.