A relationship between solar activity and planetary albedos

A significant anti-correlation between solar activity and the brightnesses of two Solar System objects has been observed. Both the planet Neptune and Saturn's satellite Titan increased in brightness by several per cent between 1972 and 1976 and subsequently became fainter by comparable amounts. This period corresponds to the decline of solar activity at the end of solar cycle 20 (1972-76), followed by the rapid increase of activity at the beginning of cycle 21. Solar minimum and the maximum observed brightness of Titan Neptune both occurred in 1976. It is suggested that what has been observed are changes in planetary albedos induced by solar activity. Such changes may have an important bearing on the energy balances of the outer planets and their satellites. (UK)