Meet the Kordylewski dust clouds, shimmering pseudo-satellites that orbit Earth near the moon. A team of Hungarian astronomers say they have spotted light scattered from one of these clouds, providing evidence that the clouds really exist after nearly 60 years of controversy.
The twin dust clouds gather at two of the points in space where the gravity of Earth and the moon cancel each other out. That gravitational stability makes these spots, called Lagrange points, good places to park spacecraft. They also could trap interplanetary debris.
No one had seen any dust clouds since 1961, when Polish astronomer Kazimierz Kordylewski reported the first sighting at two gravity holes, L4 and L5. Some astronomers thought that the sun’s stronger gravity would periodically sweep dust out of L4 and L5, making it hard for the areas to support clouds.
Astronomers Judit Slíz-Balogh, András Barta and Gábor Horváth, all of Eötvös Loránd University in Budapest, looked for the clouds using specially designed filters. These filters detect light that’s been polarized, or had its electromagnetic waves aligned, by bouncing around the dust grains.
The team spent several months making observations in Slíz-Balogh’s private observatory in the western Hungarian village of Badacsonytördemic. “It is hard to find moonless and cloudless good nights in Hungary,” the astronomers write in a paper set to be published in January in the Monthly Notices of the Royal Astronomical Society. But the team finally spotted a telltale shimmer at L5. The physics of the Lagrange points suggests that, if one cloud exists, the other does, too. The trio still wants to search for the L4 cloud directly.
Computer simulations suggest L4 and L5 are only partially stable, the team reports in a paper in the Nov. 11 MNRAS. The clouds may hang around for years or decades, but the sun’s gravity will eventually scatter them into space. That could explain the “now you see it, now you don’t” results of past searches for the clouds, the team says.
Marks the spot
Cosmic dust could gather at gravitational dead zones called Lagrange points. The L4 and L5 Lagrange points between Earth and the moon, shown in this diagram, form equilateral triangles with the Earth and the moon, and are about 400,000 kilometers from Earth.