To understand and predict the nature of planetary atmospheres, it is very important to understand their host star! Different spectral types have a wide range of UV emission, changing atmospheric photochemistry. To learn more about the effects of different main sequence stars on habitable Earth-like planets, I would suggest reviewing the work of Sarah Rugheimer, a former member of the Carl Sagan Institute.
My focus is not only on how different spectral types affect planetary environments and biosignatures, but also how stars in different evolutionary phases differ from one another.
As seen above, although Sun-like stars spend the majority of their lives on the main sequence, it spends a fair bit of time in other evolutionary stages, where different types of planetary environments could occur.
White DwarfsWhite dwarfs are the end states of stars with core masses of less than 1.4 Solar masses, which comprises the majority of the stellar population. Although they start off being extremely hot, they cool down over time and will eventually have a continuous habitable zone for long enough for life to develop and thrive on a planetary surface.
It takes approximately 10 billion years for a white dwarf to cool down from 6,000 to 4,000 K, giving life enough time to develop and evolve. My work involves simulating the climate and atmospheric photochemistry of Earth-like planets orbiting in the habitable zones of white dwarfs during this period of a continuous habitable zone. Cooler white dwarf scenarios are not included because the Universe simply isn't old enough for those to exist!