Which Albedo?

arakish

I just downloaded the trial version of Astrosynthesis 2.0. I wanted to see how accurate its calculations are (about +/- 25% off).

However, while entering a planet, on the Planet/Moon tab of the Properties box, it has a listing for albedo.

Which Albedo? V or B? There are two albedoes for a celestial object.

V-Albedo is the visual albedo or how much light the object reflects. This is the fraction when comparing the body to a perfectly diffusing object with a phase angle of 0. Commonly abbreviated V-Albedo. Earth's V-Albedo is 0.367.

B-Albedo is the bond albedo or how much energy the objects reflects without absorption. This is the fraction when comparing the body to a perfectly black body. Commonly abbreviated B-Albedo. Earth's B-Albedo is 0.306.

There is a major difference between the two. Specifically, most astronomers (myself included) refer to an object's B-albedo because this albedo is biggest determinant for the object's global average surface temperature (GAST) whether the object has an atmosphere or not. V-albedo is used to determine the object's absolute magnitude when determining how bright or dim the object is from certain distances.

Thus, I ask again: Which Albedo?

Thanks.

rmfr

Alternon

I always assumed it was bond albedo, as Astro 2 can calculate fairly decent approximations of surface temp.

Alternon

Alternon wrote:

I always assumed it was bond albedo, as Astro 2 can calculate fairly decent approximations of surface temp.

Oops, I meant visual albedo not bond albedo. If you look at the sample file that comes with Astro 2, the Local Stars file has data for Earth and shows its albedo as 0.39 (which is close).