Re: characteristics of an F7 III star

Sharc,

Thanks for an interesting question -- sorry it took me so long to answer it.

An F7 III star is not on the main sequence - the luminosity class III indicates
that it's a giant star. The type F7 means it's pretty blue for a "red giant"
star - most red giant stars in the neighbourhood of the Sun are types G, K, and
M. An F giant star would likely be very metal-poor ("metals" in the astronomical
sense of "things other than hydrogen and helium"), which means it might not be
likely to have planets.

In looking up the characteristics of an F7 III star (in "Allen's Astrophysical
Quantities", ed. A. Cox; a very useful book), the closest I could come was a G0
III star.The book says that this star has a mass of about 1 solar mass and is 6
times the radius of the Sun. The lifetime for a 1 solar mass star is about 10E9
years on the main sequence plus about 4E9 years post-main-sequence (Bowers &
Deeming, "Astrophysics I: Stars").

I hope this helps with your story. I learned from answering this question that
it's actually pretty difficult to find information on stars based on spectral
type (an observed quantity) - it's much easier to specify things like mass, age,
and metal content and find info that way.

Pauline