The Earth is far from alone on its journey around the Sun. Our most visible companion is the Moon, but there are also the thousands of artificial satellites orbiting our home planet, and the odd space rock that we drag along for the ride. Now, Hungarian astronomers have spotted two new pseudo-satellites – in the form of clouds of dust – caught in the gravitational tug-of-war between the Earth and the Moon.
The interplay of gravity between objects is more complicated than it may seem at a glance. When one large object orbits another – say, the Moon orbiting the Earth – the gravitational pull of both creates five positions, called Lagrange points, where those forces are just right to capture smaller objects. Pseudo-satellites trapped in these positions remain relatively stable in relation to each other and the larger bodies.
That stability makes these Lagrange points perfect for artificial satellites, such as NASA's DSCOVR spacecraft or future refueling stations for trips to the Moon or beyond. But, it turns out, we may be competing with nature for these strategic spots.
Polish astronomer Kazimierz Kordylewski first reported in the 1960s that clouds of interplanetary dust might gather at two of these points, known as L4 and L5. While Kordylewski apparently observed two clouds at L5, and others have reported similar sightings since, they haven't been officially confirmed to exist, mostly because they're faint and hard to detect.
To take a better look, researchers from Budapest's Eötvös Loránd University peered towards L5 with a linearly polarizing filter system, a camera lens and a Charged Couple Device (CCD) at a Hungarian observatory. This setup photographed the area, and spotted the dust through the way it scattered sunlight. That scattering pattern lined up well with previous simulations of just such a dust cloud, and the team also ruled out other optical effects creating a false positive.
"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," says Judit Slíz-Balogh, an author of the study. "It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbor."
Future research will examine the clouds more closely, and investigate how transitory they may be.
The study was published in the journal Monthly Notices of the Royal Astronomical Society.
Source: Royal Astronomical Society