SOLAR SYSTEM/Asteroids, Comets and Space Dust 227 Another glow due to cosmic dust is the Gegenschein, seen as a faint patch exactly opposite to the Sun in the sky It is extremely elusive, and is visible only under near-ideal conditions The best opportunities occur when the anti-Sun position is well away from the Milky Way, from February to April and from September to November Generally it is oval in shape, measuring about 10 by 22 , so that its maximum diameter is 40 times that of the full moon The Zodiacal Band is a very dim, parallel-sided band of radiance which may extend to either side of the Gegenschein, or prolonged from the apex of the Zodiacal Light Cone to join the Zodiacal Light with the Gegenschein It also is due to sunlight being reflected from interplanetary particles near the main plane of the Solar System See Also Solar System: The Sun; Meteorites; Mars; Jupiter, Saturn and Their Moons; Neptune, Pluto and Uranus Further Reading Figure 10 The Zodiacal Light A typical display, photographed on 19 November 1998 over the Qinghai Radio Observatory near Delinghom Qinghai, Central China (M Langbroek) who claimed that comets can actually deposit harmful bacteria in the Earth’s upper atmosphere, causing epidemics Again there has been little support Space Dust There is a great quantity of ‘dust’ in the Solar System, particularly near the main plane It is the cause of the Zodiacal Light, (Figure 10) which may be seen as a cone of light extending upwards from the horizon for a fairly brief period either after sunset or before sunrise Since it extends along the ecliptic, it is best seen when the ecliptic is nearly vertical to the horizon, in February to March and again in September–October Cometary debris is a major contributary factor It was first correctly explained by the Italian astronomer, GS Cassini, in 1683 Bone N (1986) Meteors London: Philip Bhandt G and Chapman D (1982) Introduction to Comets Cambridge: Cambridge University Press Burnfam R (2000) Great Comets Cambridge: Cambridge University Press Krishna S (1997) Physics of Comets Singapore: World Scientific Kronk G (1988) Comet Catalogue Enslow: Hillside NJ and Aldershot Kronk G (1988) Meteor Showers Enslow: Hillside NJ and Aldershot Moore P (2001) Astronomy Data Book London: Institute of Physics, Publishing Moore P (2003) Atlas of the Universe London: Philip Norton CR (1992) Rooks from Space Montana: USA Mountain Press Publishing Schmadel L (2002) Dictionary of Minor Planet Names Berlin, Heidelberg, New York: Springer verlag Kowal CT (1996) Asteroids Wiley Whipple FL (1985) The Mystery of Comets Cambridge: Cambridge University Press Yeomans K (1991) Comets New York: Wiley Science Editions