Kordylewski cloud

Kordylewski clouds are large concentrations of dust that may exist at the L4 and L5 Lagrangian points of the Earth-Moon system. They were first reported by Polish astronomer Kazimierz Kordylewski in the 1960s, but there is still controversy as to whether they actually exist, due to their extreme faintness. It is thought by some that they could be a transient phenomenon as the L4 and L5 points are unstable, due to the perturbations of the inner planets.

They were first seen visually by Kordylewski in October 1956, when he saw a glow about 2° in angular size and half as bright as the Gegenschein. He then photographed them in 1961 when they seemed to change in size and shape. In 1967 J. Wesley Simpson made observations using the Kuiper Airborne Observatory.

If they are in fact 2° angular size as seen from Earth, they could be at least 14000 km (8700 miles) across, about the size of the Earth.

References

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* [http://www.seds.org/billa/tnp/hypo.html#moon2 Hypothetical Planets]
* [http://www.rfreitas.com/Astro/SearchIcarus1983.htm A Search for Objects near the Earth-Moon Lagrangian Points] , by Francisco Valdes and Robert A. Freitas Jr., did not find any objects at the Earth-Moon or Earth-Sun lagrange points, but this survey was not sensitive to diffuse clouds.

ee also

*Trojan asteroid