Bond albedo explained

The Bond albedo (also called spheric albedo, planetary albedo, and bolometric albedo), named after the American astronomer George Phillips Bond (1825–1865), who originally proposed it, is the fraction of power in the total electromagnetic radiation incident on an astronomical body that is scattered back out into space.

Because the Bond albedo accounts for all of the light scattered from a body at all wavelengths and all phase angles, it is a necessary quantity for determining how much energy a body absorbs. This, in turn, is crucial for determining the equilibrium temperature of a body.

Because bodies in the outer Solar System are always observed at very low phase angles from the Earth, the only reliable data for measuring their Bond albedo comes from spacecraft.

Phase integral

The Bond albedo (A) is related to the geometric albedo (p) by the expression

A=pq

where q is termed the phase integral and is given in terms of the directional scattered flux I(α) into phase angle α (averaged over all wavelengths and azimuthal angles) as

q=

\pi
2\int
0
I(\alpha)
I(0)

\sin\alphad\alpha.

The phase angle α is the angle between the source of the radiation (usually the Sun) and the observing direction, and varies from zero for light scattered back towards the source, to 180° for observations looking towards the source. For example, during opposition or looking at the full moon, α is very small, while backlit objects or the new moon have α close to 180°.

Examples

The Bond albedo is a value strictly between 0 and 1, as it includes all possible scattered light (but not radiation from the body itself). This is in contrast to other definitions of albedo such as the geometric albedo, which can be above 1. In general, though, the Bond albedo may be greater or smaller than the geometric albedo, depending on the surface and atmospheric properties of the body in question.

Some examples:[1]

Name Bond albedo Visual geometric albedo
Mercury[2] [3]
Venus[4]
Earth[5]
Moon[6]
Mars [7]
Jupiter[8]
Saturn[9]
Enceladus[10] [11]
Uranus[12]
Neptune[13]
Pluto[14]
Charon[15]
Haumea
Makemake
Eris

See also

External links

Notes and References

  1. http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo of the Earth
  2. The spherical bolometric albedo for planet Mercury . Anthony . Mallama . 2017 . astro-ph.EP . 1703.02670 .
  3. Comprehensive wide-band magnitudes and albedos for the planets, with applications to exo-planets and Planet Nine . Icarus . Anthony . Mallama . Bruce . Krobusek . Hristo . Pavlov . 282 . 19–33 . 2017 . 10.1016/j.icarus.2016.09.023 . 1609.05048 . 2017Icar..282...19M . 119307693 .
  4. Radiative energy balance of Venus based on improved models of the middle and lower atmosphere . Icarus . R. . Haus . etal . 272 . 178–205 . July 2016 . 10.1016/j.icarus.2016.02.048 . 2016Icar..272..178H .
  5. Web site: Williams. David R.. 2004-09-01. Earth Fact Sheet. NASA. 2010-08-09.
  6. Web site: Williams. David R.. 2014-04-25. Moon Fact Sheet. NASA. 2015-03-02.
  7. http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html Mars Fact Sheet, NASA
  8. Less absorbed solar energy and more internal heat for Jupiter . Liming . Li . etal . Nature Communications . 2018 . 10.1038/s41467-018-06107-2 . 30213944 . 9 . 1 . 6137063 . 3709 . 2018NatCo...9.3709L.
  9. Albedo, internal heat flux, and energy balance of Saturn . R.A. . Hanel . etal . Icarus . 53 . 262–285 . 1983 . 2 . 10.1016/0019-1035(83)90147-1 . 1983Icar...53..262H .
  10. Verbiscer. A.. French. R.. Showalter. M.. Helfenstein. P.. Enceladus: Cosmic Graffiti Artist Caught in the Act. Science. 315. 5813. 815. February 9, 2007. 17289992. 2007Sci...315..815V. 10.1126/science.1134681. 21932253. . (supporting online material, table S1)
  11. Thermal inertia and bolometric Bond albedo values for Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus as derived from Cassini/CIRS measurements . Howett . Carly J. A. . Spencer . John R. . Pearl . J. C. . Segura . M. . 2010 . Icarus . 206 . 2 . 573–593 . 10.1016/j.icarus.2009.07.016 . 2010Icar..206..573H.
  12. The albedo, effective temperature, and energy balance of Uranus, as determined from Voyager IRIS data . J.C. . Pearl . etal . Icarus . 84 . 12–28 . 1990 . 1 . 10.1016/0019-1035(90)90155-3 . 1990Icar...84...12P .
  13. The albedo, effective temperature, and energy balance of Neptune, as determined from Voyager data . J.C. . Pearl . etal . J. Geophys. Res. . 96 . 18,921-18,930 . 1991 . 10.1029/91JA01087 . 1991JGR....9618921P .
  14. etal . Anne J. . Verbiscer . Paul . Helfenstein . Simon B. . Porter . Susan D. . Benecchi . J. J. . Kavelaars . Tod R. . Lauer . The Diverse Shapes of Dwarf Planet and Large KBO Phase Curves Observed from New Horizons . The Planetary Science Journal . April 2022 . 3 . 4 . 95 . 31 . free . 10.3847/PSJ/ac63a6 . 2022PSJ.....3...95V.
  15. Buratti . B. J. . Hicks . M. D. . Hillier . J. H. . Verbiscer . A. J. . Abgarian . M. . Hofgartner . J. D. . Lauer . T. R. . Grundy . W. M. . Stern . S. A. . Weaver . H. A. . Howett . C. J. A. . 2019-03-19 . New Horizons Photometry of Pluto's Moon Charon . The Astrophysical Journal . 874 . 1 . L3 . 10.3847/2041-8213/ab0bff . 2019ApJ...874L...3B . 127098911 . 2041-8213. free .

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