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The opposition effect is the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer. It is so named because the reflected light from the Moon and Mars appears significantly brighter than predicted when at astronomical opposition, giving rise to an opposition spike. It is due to light reflected from the surface's small pores and pits that would otherwise be in shadow at other incidence angles, or, in the case of Saturn's rings, due to all particles visible being fully illuminated and not shadowed. It does not arise from smooth mirror-like surfaces, which give rise to a different anti-solar brightening, nor from completely cloudy planets such as Jupiter.^{[citation needed]} Wikipedia does not have an article with this exact name. ... The term opposition spike refers to the surge in a planetary bodys apparent magnitude as it reaches astronomical opposition with respect to an observer. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ... For the Roman god, see Mars (mythology). ... Opposition is a term used in positional astronomy and astrology to indicate when one celestial body is on the opposite side of the sky when viewed from a particular place (usually the Earth). ... The term opposition spike refers to the surge in a planetary bodys apparent magnitude as it reaches astronomical opposition with respect to an observer. ...

See also

• Opposition spike - the observed increase in astronomical magnitude due to this effect

The term opposition spike refers to the surge in a planetary bodys apparent magnitude as it reaches astronomical opposition with respect to an observer. ...

External link

• opposition effect, its mechanism and examples
• Opposition Surge on the B Ring - as seen by Cassini-Huygens