Answer:
Recall that stars are classified with types from the spectra sequence OBAFGKM. In general, an ordinary (hydrogen-fusing, or main-sequence) star of spectral type A is hotter than a star of spectral type K.
Explanation:
The Harvard classification system (OBAFGKM) is a sequence of temperature, in which type O correspond to a star with an effective temperature around 50000K and type M to a star with an effective temperature of 3000K. This classification is made by an analysis of the spectrum¹ of the star and by searching for spectral lines which are dependent to temperature.
Each spectral type will have different lines that are stronger as a consequence of the temperature of the type. For example, the Hydrogen lines are more intense in the type A than in others spectral types (OBFGKM).
It is important to know that the spectral lines in a star's spectrum are created when the light coming from the inner parts of the star interacts with the elements that are in its atmosphere. Â Â Â
Since the letters to the left represents higher temperatures that the ones to right in the Harvard classification system (OBAFGKM) it is correct to say that a star of spectral type A is hotter than a star of spectral type K.
Key terms:
¹Spectrum: Decomposition of light in its characteristic colors (wavelengths).
