Short answers, pulled from the story.
An F-type main-sequence star is a core-hydrogen-fusing star of spectral type F with a surface temperature between about 6,000 and 7,200 Kelvin. These stars have masses ranging from about 1.1 to 1.6 times that of the Sun and appear white from space due to their higher temperature. Notable examples include Procyon A, Gamma Virginis A and B, and Tabby's Star.
F-type stars spend approximately 2-6 billion years on the main sequence, significantly less than the roughly 10 billion years a G-type star like the Sun remains there. After exhausting the hydrogen in their cores, they expand into red giants, shed their outer layers to form a planetary nebula, and leave behind a hot white dwarf.
The two anchor points of the MK spectral classification system among F-type dwarf stars are 78 Ursae Majoris, classified as F2 V, and Pi Orionis, classified as F6 V. These stars have remained stable standards over many years and are used to define the classification system itself.
Some studies indicate life could potentially develop around F-type stars, but ultraviolet radiation poses a major challenge. A planet at the equivalent habitable distance from an F-type star could receive approximately 2.5 to 7.1 times more UV damage than Earth receives from the Sun. Life would likely need a denser ozone layer, or be confined to underwater or underground environments, or have adapted external protective coverings such as shells.
The habitable zone around an F0 star is estimated to extend from about 2.0 AU to 3.7 AU from the star, and from about 1.1 to 2.2 AU for a cooler F8 star. These distances are farther out than Earth's position from the Sun, reflecting the greater luminosity of F-type stars.
F-type subdwarfs are luminosity class VI stars of spectral type F that fall up to two magnitudes below the main sequence due to their low metallicity, making them less luminous than typical F-type main-sequence stars. Like normal F-type dwarfs, they still fuse hydrogen in their cores, but they are much less common than subdwarfs of the cooler G, K, and M spectral classes.