Class F — F-type (Yellow-White)

F-type stars are yellow-white stars with surface temperatures of 6,000 to 7,500 K. They make up about 3% of main-sequence stars. Their spectra show weakening hydrogen lines and strengthening calcium and iron lines compared to A-type stars. Notable examples include Canopus (F0II), the second-brightest star, and Procyon (F5IV-V). F-type stars are of great interest in the search for habitable exoplanets because their habitable zones are wider than those of cooler stars. They live for 2-4 billion years.

F-type stars bridge the gap between the hot A-types and the Sun-like G-types, with surface temperatures between 6,000 and 7,500 K. Comprising about 3% of main-sequence stars, they appear yellow-white and are of particular interest to exoplanet researchers because their habitable zones are wider than the Sun's while their lifetimes (2-7 billion years) are potentially long enough for complex life to evolve — though this remains a topic of active debate in astrobiology.

Characteristics

F-type spectra show weakening hydrogen lines and strengthening metal lines, particularly the ionized calcium H and K lines that become increasingly prominent toward later spectral types. F stars mark the transition where convective envelopes first appear, enabling magnetic activity and stellar cycles similar to the Sun's. The late-F stars (F5-F9) show measurable chromospheric activity and starspots. F stars have masses of 1.04-1.4 solar masses and luminosities of 1.5-5 times solar, making them easy targets for radial velocity exoplanet surveys.

Notable Examples

Procyon (Alpha Canis Minoris, F5IV-V) is the eighth-brightest star, a nearby F-type subgiant at 11.5 light-years with a white dwarf companion. Canopus (Alpha Carinae, F0Ib), the second-brightest star in the sky, is actually an F-type supergiant — enormously luminous at 10,700 solar luminosities. Polaris (Alpha Ursae Minoris, F7Ib) is an F-type supergiant and Cepheid variable, famous as the current North Star. The Cepheid period-luminosity relationship, crucial for measuring cosmic distances, was discovered using F and G-type Cepheid variables.

HIP 84761HIP 84762HIP 84766HIP 95905HIP 822HIP 4625HIP 4629HIP 53149HIP 71227HIP 71231HIP 29421HIP 29438HIP 29439HIP 29444HIP 29449HIP 29452HIP 29453HIP 95925HIP 95927HIP 95930HIP 95938HIP 95939HIP 4637HIP 4647HIP 4650HIP 4660HIP 4662HIP 53156HIP 46230HIP 46235HIP 46236HIP 46243HIP 55904HIP 46253HIP 46256HIP 46257HIP 46269HIP 53161HIP 46285HIP 46294HIP 46306HIP 55908HIP 55909HIP 46308HIP 46309HIP 46310HIP 46312HIP 46321

Frequently Asked Questions

What is a class F star?
Class F (F-type (Yellow-White)) stars are yellow-white stars. F-type stars are yellow-white stars with surface temperatures of 6,000 to 7,500 K. They make up about 3% of main-sequence stars. Their spectra show weakening hydrogen lines and strengthening calcium a
How hot are class F stars?
Class F stars have surface temperatures between 6,000 K and 7,500 K.
What color are class F stars?
Class F stars appear yellow-white.
How many class F stars are in the StarFYI database?
StarFYI currently catalogs 25,601 class F stars.
How luminous are class F stars?
Moderate, 1.5-5 solar luminosities