One or two ghostly dust satellites could orbit the earth, according to a new research report on a 60-year-old idea.
Massive objects attract by gravity. But if you have several huge objects with just the right masses, their common gravitational field can cause some anomalies – such as gravity points – that can keep things stable. Scientists have found objects orbiting in these "Lagrange points" created by the combined gravitation of Sun and Mars, Sun and Neptune, Sun and Jupiter. Researchers now report dust clouds called Kordylewski dust clouds in the Lagrange points created by Earth and the Moon.
The Swiss mathematician Leonhard Euler prophesied in 1767 the first three Lagrange points in such systems and the Italian astronomer Joseph -Louis Lagrange predicted 1772 two more points. Today, scientists know all about them – the upcoming NASA Space Telescope James Webb orbits the Sun and Earth in a stable Lagrange point called L2.
The Earth and the Moon are in the right proportions, so that a certain amount of mass stably encircles the system at L4 and L5, the two Lagrange points that Lagrange himself discovered. The Polish scientist Kazimierz Kordylewski found evidence of dust clouds in 1961 near L5. Since then, these dust clouds have hardly been explored. But in the last two months, teams of scientists have been investigating whether these clouds might exist, even though the additional gravity of the sun or its solar winds may blast away such a cloud.
The Eötvös Loránd University team began building a mathematical simulation based on the equations of a system containing the Sun, Earth, Moon, and a fourth dust cloud. They found that a swirling, ever-changing cloud of dust was completely possible at L5, according to the first of two essays in the Monthly Reports of the Royal Astronomical Society. This was confirmed by another analysis by a team of Russian scientists published a month earlier.
But would they actually see a Kordylewski cloud? The team began with the private observatory of study author Judit Slíz-Balogh in Badacsonytördemic, Hungary, with special lenses that could measure the polarization of the light – essentially the orientation of its corresponding electric field as it traveled through space. They hoped that they could see the signature of the Kordylewski dust cloud on the polarization of the light coming from L5.
They found it, but not without effort. "After a few months of perseverance (because it is difficult to find moonless and cloudless good nights in Hungary), we have succeeded [Kordylewski dust cloud] around the Lagrange point L5 on two consecutive nights, "they wrote in the second newspaper, which was published in the Monthly Reports of the Royal Astronomical Society.
Although the team has the modeling and observation to support it, it is still worth treating their conclusion with a grain of salt. According to the report, their observations may be a transitory phenomenon, and any dust they saw could easily be blown away by gravitational orbital impacts from other planets or solar winds. Many other telescopes, as well as a Japanese probe, have found no evidence of the dust – although others have observations. Perhaps it is something else, though the researchers have been careful to exclude other possible sources of this polarized light. Researchers argue that their polarization-observing method provides a better way to find the dust cloud.
So, is the cloud really there? The latest evidence points to yes – and if it really is there, that means we have at least one, if not two goblets, with another possible dust cloud at L4. Spoooooky!