We attempted to detect the Earth-Moon libration clouds around L4 with a cooled CCD camera at Mauna Kea (4200m), Hawaii, on November 17 and 18, 1999. No significant enhancement of brightness larger than 1.5S10⊙ was found around L4. It seems that the brightness of the libration clouds in 1999, if it existed, would be fainter than that reported previously by Kordylewski and Roach.
The Lagrangian points L4 and L5 are the triangular solutions of the restricted three-body problem. The L4 is located in the leading side and the L5 in the trailing side of an orbit. In the solar system, it is widely known that certain asteroids called the “Trojan family” exist around the Sun-Jupiter Lagrangian points. It is also known that (5261) Eureka is a Mars Trojan. Kuchner et al. tried to find the dust clouds around the Sun-Jupiter L5 point by analysing the COBE-DIRBE infrared data, but they obtained a negative result.