What is the difference between albedo and Bond albedo?

Question

Recently I came across Bond albedo, but I am not sure I grasped the difference (if there is any) between it and the "classical" albedo. Thanks in advance

Answer 1

When we talk about "albedo" we normally think in terms of how much visible light is reflected. A "white" object would reflect nearly all visible light, and have an albedo close to 1.

But that "white" object might absorb infra-red and ultra-violet light. Consider the stuff that sunblock is made from. It is white or transparent to visible light, but absorbs most UV. It would appear black to a UV camera.

The bond albedo includes the absorption/reflection/re-emmision at all wavelengths. It also includes the total absorbed or reflected at all angles. That's important because many objects are significantly retro-reflective and reflect more directly back than is scattered sidewise. If you want to know how bright an object will appear in your (visible light) telescope you want the ordinary albedo, but if you are interested in studying how warm a solar system body will be, then you need the bond albedo.

As a further example, the increase in CO2 in the Earth's atmosphere tends to lower the bond albedo. The Earth absorbs more of the sun's heat as a result of an increased greenhouse effect. But as CO2 is transparent at visible wavelengths, it doesn't change the classical albedo.