Editing Albedo (section)

===Optical or visual albedo===
The albedos of [[planet]]s, [[Natural satellite|satellites]] and [[minor planet]]s such as [[asteroid]]s can be used to infer much about their properties. The study of albedos, their dependence on wavelength, lighting angle ("phase angle"), and variation in time composes a major part of the astronomical field of [[photometry (astronomy)|photometry]]. For small and far objects that cannot be resolved by telescopes, much of what we know comes from the study of their albedos. For example, the absolute albedo can indicate the surface ice content of outer [[Solar System]] objects, the variation of albedo with phase angle gives information about [[regolith]] properties, whereas unusually high radar albedo is indicative of high metal content in [[asteroid]]s.

[[Enceladus]], a moon of Saturn, has one of the highest known optical albedos of any body in the Solar System, with an albedo of 0.99. Another notable high-albedo body is [[Eris (dwarf planet)|Eris]], with an albedo of 0.96.<ref name="sicardy">
{{cite journal
| title = Size, density, albedo and atmosphere limit of dwarf planet Eris from a stellar occultation
| journal = European Planetary Science Congress Abstracts
| volume = 6
| date = 2011
| url = http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-137-8.pdf
| access-date = 14 September 2011
| bibcode = 2011epsc.conf..137S
| last1 = Sicardy
| first1 = B.
| last2 = Ortiz
| first2 = J. L.
| last3 = Assafin
| first3 = M.
| last4 = Jehin
| first4 = E.
| last5 = Maury
| first5 = A.
| last6 = Lellouch
| first6 = E.
| last7 = Gil-Hutton
| first7 = R.
| last8 = Braga-Ribas
| first8 = F.
| last9 = Colas
| first9 = F.
| page = 137
| display-authors=8
}}
</ref> Many small objects in the outer Solar System<ref name="tnoalbedo">{{cite web
  |date=17 September 2008
  |title=TNO/Centaur diameters and albedos
  |publisher=Johnston's Archive
  |author=Wm. Robert Johnston
  |url=http://www.johnstonsarchive.net/astro/tnodiam.html
  |access-date=17 October 2008| archive-url= https://web.archive.org/web/20081022223827/http://www.johnstonsarchive.net/astro/tnodiam.html| archive-date= 22 October 2008<!--Added by DASHBot-->}}</ref> and [[asteroid belt]] have low albedos down to about 0.05.<ref name="astalbedo">{{cite web
  |date=28 June 2003
  |title=Asteroid albedos: graphs of data
  |publisher=Johnston's Archive
  |author=Wm. Robert Johnston
  |url=http://www.johnstonsarchive.net/astro/astalbedo.html
  |access-date=16 June 2008| archive-url= https://web.archive.org/web/20080517100307/http://www.johnstonsarchive.net/astro/astalbedo.html| archive-date= 17 May 2008<!--Added by DASHBot-->}}</ref> A typical [[comet nucleus]] has an albedo of 0.04.<ref name="dark">{{cite news
  |date=29 November 2001
  |title=Comet Borrelly Puzzle: Darkest Object in the Solar System
  |work=Space.com
  |author=Robert Roy Britt
  |url=http://www.space.com/scienceastronomy/solarsystem/borrelly_dark_011129.html
  |access-date=1 September 2012| archive-url= https://web.archive.org/web/20090122074028/http://www.space.com/scienceastronomy/solarsystem/borrelly_dark_011129.html| archive-date= 22 January 2009}}</ref> Such a dark surface is thought to be indicative of a primitive and heavily [[space weathering|space weathered]] surface containing some [[organic compound]]s.

The overall albedo of the [[Moon]] is measured to be around 0.14,<ref name="CERESmoon">
{{cite journal
| title = Celestial body irradiance determination from an underfilled satellite radiometer: application to albedo and thermal emission measurements of the Moon using CERES
| journal = Applied Optics
| volume = 47 | issue = 27
| date = 2008
| bibcode = 2008ApOpt..47.4981M
| last1 = Matthews
| first1 = G.
| pages = 4981–4993
|doi = 10.1364/AO.47.004981
| pmid=18806861}}
</ref> but it is strongly directional and non-[[Lambertian reflectance|Lambertian]], displaying also a strong [[opposition effect]].<ref name="medkeff" /> Although such reflectance properties are different from those of any terrestrial terrains, they are typical of the [[regolith]] surfaces of airless Solar System bodies.

Two common optical albedos that are used in astronomy are the (V-band) [[geometric albedo]] (measuring brightness when illumination comes from directly behind the observer) and the [[Bond albedo]] (measuring total proportion of electromagnetic energy reflected). Their values can differ significantly, which is a common source of confusion.

{| class="wikitable"
|-
! Planet
! Geometric
! Bond
|-
| Mercury
| 0.142 <ref name="Mallama_et_al"/>
| 0.088 <ref name="Mallama"/> or 0.068
|-
| Venus
| 0.689 <ref name="Mallama_et_al"/>
| 0.76  <ref name="Haus_et_al"/> or 0.77
|-
| Earth
| 0.434 <ref name="Mallama_et_al"/>
| 0.294 <ref>{{cite web|url =http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html |title =Earth Fact Sheet|website = NASA|first = David R.|last = Williams |date = 11 January 2024}}</ref>
|-
| Mars
| 0.170 <ref name="Mallama_et_al"/>
| 0.250 <ref>{{cite web|url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html |title =Mars Fact Sheet|website = NASA|first = David R.|last = Williams |date = 25 November 2020}}</ref>
|-
| Jupiter
| 0.538 <ref name="Mallama_et_al"/>
| 0.343±0.032 <ref>{{cite web|url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html |title =Jupiter Fact Sheet|website = NASA|first = David R.|last = Williams |date = 11 January 2024}}</ref> and also 0.503±0.012 <ref name="Li_et_al"/>
|-
| Saturn
| 0.499 <ref name="Mallama_et_al"/>
| 0.342 <ref name="Hanel_et_al"/>
|-
| Uranus
| 0.488 <ref name="Mallama_et_al"/>
| 0.300 <ref name="Pearl_et_al_Uranus"/>
|-
| Neptune
| 0.442 <ref name="Mallama_et_al"/>
| 0.290 <ref name="Pearl_et_al_Neptune"/>
|}

In detailed studies, the directional reflectance properties of astronomical bodies are often expressed in terms of the five [[Hapke parameters]] which semi-empirically describe the variation of albedo with [[phase angle (astronomy)|phase angle]], including a characterization of the opposition effect of [[regolith]] surfaces. One of these five parameters is yet another type of albedo called the [[single-scattering albedo]]. It is used to define scattering of electromagnetic waves on small particles. It depends on properties of the material ([[refractive index]]), the size of the particle, and the wavelength of the incoming radiation.

An important relationship between an object's astronomical (geometric) albedo, [[Absolute magnitude#Absolute magnitude for planets (H)|absolute magnitude]] and diameter is given by:<ref name="bruton">{{cite web
 |title=Conversion of Absolute Magnitude to Diameter for Minor Planets
 |publisher=Department of Physics & Astronomy (Stephen F. Austin State University)
 |author=Dan Bruton
 |url=http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html
 |access-date=7 October 2008
 |archive-url=https://web.archive.org/web/20081210190134/http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html
 |archive-date=10 December 2008
 |url-status=dead
}}</ref>
<math display="block">A =\left ( \frac{1329\times10^{-H/5}}{D} \right ) ^2,</math>
where <math>A</math> is the astronomical albedo, <math>D</math> is the diameter in kilometers, and <math>H</math> is the absolute magnitude.