Scientists think they may have identified clumps of interplanetary dust orbiting Earth, a dust moon if you will, first theorized almost 60 years ago.
Publishing their study in the Monthly Notices of the Royal Astronomical Society (MNRAS), a team of Hungarian researchers say they found evidence for two clouds of dust near Earth. These are located about 400,000 kilometers (250,000 miles) from our planet, roughly comparable to the distance of the Moon.
The clouds of dust are believed to be in regions of gravitational stability, known as Lagrange points L4 and L5, caused by the gravity of Earth and the Moon. These points move around Earth as the Moon orbits, forming a triangle. The dust clouds "move ahead of and behind the moon in orbit," noted EarthSky.
In 1961, Polish astronomer Kazimierz Kordylewski first saw hints of a faint dust cloud at L5. However, as the clouds are extremely faint, it has been difficult to prove these findings.
But in the paper published in MNRAS, the astronomers used a private observatory belonging to study co-author Judit Slíz-Balogh in Badacsonytördemic, Hungary to hunt them down. They took long exposures of L5, showing that light was basically reflecting off the dust.
These observations matched a prediction made by researchers in another paper, while also matched the observations of Kordylewski. The team ruled out Earth-based interference as being the cause of the reflection too, seemingly pointing to the dust cloud explanation.
"The Kordylewski clouds are two of the toughest objects to find, and though they are as close to Earth as the Moon are largely overlooked by researchers in astronomy,” Slíz-Balogh said in a statement. “It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbour."
It’s not all done and dusted (sorry), though. The team noted in their paper that these clumps of dust could simply be passing by – we don’t know for sure that they’re stuck in the L4 or L5 positions. Other attempts to find these dust moons have not been successful.
“The KDC [Kordylewski dust clouds] may be a transient [short-lived] phenomenon,” the team wrote in their paper. “[T]he probability of dust particles being trapped is random due to the occasional incoming of particles and their incidental velocity vectors. Therefore, the structure and particle density of the KDC is not constant.”
Still, it’s an interesting finding, and if true suggests there’s more going on near Earth than we thought. And the team even suggest future missions could sample the dust in these regions, while learning more about them could help other spacecraft avoid hitting the dust.