Since the 1950s, astronomers have speculated that Earth might have one if not two temporary satellites out in the moon’s orbital path. These neighbors were theorized to have been made of dust, which made observing and studying them difficult. Now, in 2018, astronomers have finally been able to confirm the existence of one of these mysterious orbiting bodies.
A bit of physics to start us off
Every orbital system of two bodies contains a set of stable points called Lagrange points. Whether you’re observing the dynamic between a double star pair, the sun, and Mercury, or Earth and its moon, all of these systems contain Lagrange points where the two gravitational pulls cancel out and create a harmonious bubble.
Earth and its moon have five such pockets of gravitational neutrality: One on the near side of our satellite, one on the far side, one on the moon’s orbital path on the opposite side of Earth, and two long ones along its orbital path on the near side of the planet. The two elongated Lagrangian zones, L4 and L5, are where scientists believe our dusty satellites are hiding.
The Kordylewski clouds, two masses of dust and other small particles, are believed to be situated along the moon’s orbital path in L4 and L5. Seeing as they’re made of small particles, observing them is quite tricky. What makes them even harder to study is the fact that they disappear and reform on a regular basis as the sun’s gravitational field disrupts the Lagrange points, and solar winds blow the dust around.
Until very recently, the existence of these clouds has been the source of heated debate. Multiple observations have been reported since the 1950s, but a probe sent to test dust concentrations in L4 and L5 was unable to report any unusual findings.
In October of 2018, the existence of one Kordylewski cloud at L5 was confirmed with a photograph by astronomers. Any mass of particles that might exist at L4 has yet to be verified. While the clouds can be viewed from Earth, it is a challenging task. They are very dim and have a reddish appearance relative to their black backdrop.
Scientists hope to confirm or deny the existence of a second Kordylewski cloud at the Earth-moon system‘s fourth Lagrange point soon. In the meantime, if one wishes to view the cloud at L5, they need to find themselves pristine black skies and a clear night.