Moon
© Reuters / NASA
As far as we know, we're still alone in the solar system, but now our moon has company. Hungarian astronomers have confirmed two "moons" made entirely of dust are orbiting Earth, catching the long-rumored satellites on film.

Researchers have suspected the moons were there since 1961, when Polish astronomer Kazimierz Kordylewski spotted the two bright spots, but their existence remained controversial.

The Kordylewski clouds are about nine times wider than earth, though their component particles are microscopic. Sunlight reflecting off the particles makes them glow, but they are difficult to see from Earth due to the comparative brightness of other objects in space.

Putting to rest years of speculation, researchers Judit Slíz-Balogh and Gábor Horváth of Eötvös Loránd University finally immortalized the clouds on film using special polarizing filters on their cameras. Their findings have been published in the Monthly Notices of the Royal Astronomical Society.

The clouds form when particles in space are trapped in "Lagrange points" - areas where the gravitational pull of two competing orbits balances out, holding the particles in relative stasis at a constant distance from the two bodies. Astronomers have identified five such points in the vicinity of Earth. The two clouds photographed by the researchers were located near the L5 point, and they believe there may be similar formations near L4.

Kordylewski cloud
© J. Slíz-Balogh / Royal Astronomical Society
The central region of Kordylewski cloud.
Because Lagrange points are relatively stable, they are ideal parking spots for satellites, which then require minimal fuel to stay in orbit. As space agencies look toward Mars as the next frontier, Lagrange points could also serve as rest stops on an 'interplanetary superhighway' to the red planet. Confirmation of the Kordylewski clouds' existence becomes an important safety factor in setting up such missions.

While the Lagrange points themselves are stable, the particles comprising the clouds are constantly being swapped out with other interplanetary matter, including from meteor showers. Such constant motion must be taken into account when navigating nearby space.