Hungarian astronomers have confirmed the existence of dust clouds orbiting the Earth at approximately 400,000 km. The clouds named after their discoverer, polish astronomer Kazimierz Kordylewski, exist in semi-stable points in the Earth/Moon gravitational system and have thus far been a point of contention amongst astronomers due to their faintness.

The discovery follows work earlier this year by a Hungarian team led by Gábor Horváth of Eötvös Loránd University, which modeled the Kordylewski clouds to assess how they form and how they might be detected. The clouds were suspected to be located at semi-stable points in the Earth/Moon system known as LaGrangian points (in this case the points L4 and L5).

Artist’s impression of the Lagrangian points L5 and L4 where Kordylewski clouds are believed to exist (Credit: G. Horváth)

These points form an equal-sided triangle with the Earth and Moon and move around the Earth with the Moon. Despite only being semi-stable due to the Sun’s gravitational influence, scientists believe these are the ideal points for interplanetary dust to collect.

Kordylewski observed two nearby clusters of dust at L5 in 1961 and there have been multiple reports of similar observations since, but their extreme faintness makes them difficult to detect and many scientists doubted their existence.

Researchers aimed to examine the appearance of the clouds using polarising filters similar to those found in common sunglasses which only allow the transmission of light orientated (or polarised) at a specific angle. The researchers then set out to find the dust clouds with a linearly polarising filter system attached to a camera lens and CCD detector at a private observatory in Hungary.

The astronomers used the set-up to take various images of the L5 point, obtaining evidence of polarised light reflected from dust extending well outside the field view of the camera lens. The patterns within the images conform well to both previous predictions and the observations made of Kordylewski clouds at L5 made in 1961.

The team was able to rule out the possibility of the effect being due to photographic artifacts, thus seemingly confirming the existence of Kordylewski clouds.

Judit Slíz-Balogh, owner of the private observatory where the discovery was made said:

“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. It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbor.”

The discovery is significant as research into the semi-stable LaGrangian points L4 and L5 could well be extremely important to the development and placement of space probes, satellites, and other such equipment. The points have even been suggested as transfer points to be used in the further exploration of the solar system.

Future research into the points will examine just how stable these points are and the potential risk that Kordylewski clouds may pose to both equipment and astronauts.

These new findings can be found in two papers:

Celestial mechanics and polarization optics of the Kordylewski dust cloud in the Earth-Moon Lagrange point L5 — Part I. Three-dimensional celestial mechanical modelling of dust cloud formation”, J. Slíz-Balogh, A. Barta and G. Horváth, Monthly Notices of the Royal Astronomical Society (2018), 480 (4): 5550–5559 (DOI: 10.1093/mnras/sty2049)

Celestial mechanics and polarization optics of the Kordylewski dust cloud in the Earth-Moon Lagrange point L5. Part II. Imaging polarimetric observation: new evidence for the existence of Kordylewski dust cloud”, J. Slíz-Balogh, A. Barta and G. Horváth, Monthly Notices of the Royal Astronomical Society (2018), in press (DOI: 10.1093/mnras/s

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