The F-type is a bright yellow-white star in the middle of the spectral sequence. These stars are distinguished by ionized calcium increasing in strength, hydrogen weakening, and other elements also beginning to strengthen as one goes down the scale.
These stars are very like Sol, although somewhat hotter and brighter and more shorter-lived. A F0 type star generally has a mass of about 1.7 times that of Sol, a luminosity of about 6.3 times, a surface temperature of some 7,400 Kelvin, and will spend about 3 billion years on the main sequence. The F5 spectral type is only about 1.3 times as massive and 2.5 times as luminous as Sol, with a surface temperature of around 6,600K. The cooler (F5 to F9) of these stars are prime candidates for natural garden worlds, but life, when found, is often of the microbial type due to the relative youth of the system. Nevertheless, these worlds can be easily terraformed, and the solar systems of F-types are valued by development corporations and colonists.