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Diagram showing the Lagrangian points of the Earth – Moon system. If they exist, the Kordylewski clouds lie in the L4 and L5 regions. Image via Wikimedia Commons.
The Royal Astronomical Society (RAS) said this week (October 25, 2018) that astronomers may have now confirmed the existence of two elusive dust clouds, gravitating around the Earth roughly at the distance of the moon. They are known as Kordylewski clouds, reported for the first time by the Polish astronomer Kazimierz Kordylewski and named in 1961. If it exists, Earth's dust-cloud satellites are exceptionally weak, so their existence is controversial. RAS launches two new articles on clouds Kordylewski in his peer-reviewed journal Monthly Notices from the Royal Astronomical Society. In a statement, a team of Hungarian astronomers and physicists could have confirmed the clouds where Kordylewski had announced it, at semi-stable points 400,000 km from the Earth.
By way of comparison, the average distance of the moon is 385,000 km (238,900 miles) from the Earth.
Enlarge image | Artist concept of a Kordylewski cloud in the night sky at the time of observations. The brightness is greatly improved; we would not really see this cloud. Image via G. Horváth / RAS.
If they exist, Kordylewski clouds are located in two particular places of the Earth-Moon system. These points – known as Lagrange or Lagrange points – are known to be relatively stable by gravitation. Objects, even dust, that drift close to these points would tend to move neither to Earth nor to the moon. They tend to stay in place, moving in front of and behind the moon in orbit. The RAS explained:
Two of these so-called Lagrange points, L4 and L5, form an even triangle between the Earth and the Moon and move around the Earth as the Moon moves on its orbit.
L4 and L5 are not completely stable because they are disturbed by the gravitational attraction of the sun. Nevertheless, it is thought that these are places where interplanetary dust could accumulate, at least temporarily. Kordylewski observed two clusters of dust near L5 in 1961, with different reports since then, but their extreme weakness makes them difficult to detect and many scientists have questioned their existence.
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In an article published in early 2018, the Hungarian team, led by Gábor Horváth of Eötvös Loránd University, modeled Kordylewski clouds to assess their formation and eventual detection. Researchers looked at their appearance using polarizing filters, similar to those found on some types of sunglasses. The RAS explained:
The scattered or reflected light is always more or less polarized depending on the angle of diffusion or reflection.
After determining what to look for, the researchers then began to find the dust clouds. They set up a linear polarization filter system, attached to a camera and a CCD detector, in the Slíz-Balogh private observatory in Hungary (Badacsonytördemic).
Next, scientists took views of the alleged location of the Kordylewski cloud at point L5.
The images they obtained show a polarized light reflected by the dust, extending well outside the field of view of the camera lens. The SAR said:
The model observed corresponds to the predictions made by the same group of researchers in a previous article and corresponds to the first observations of Kordylewski's clouds six decades ago.
The Horvath group was able to exclude optical artifacts and other effects, which means that the presence of the dust cloud is confirmed.
Diagram of the polarization angle of the sky around the Lagrange point L5 of the Earth-Moon system. Image acquired on August 19, 2017. The position of point L5 is indicated by a white dot. In this image, the central region of the Kordylewski dust cloud is visible (bright red pixels). Inclined straight lines are traces of satellites. Image via J. Slíz-Balogh / RAS.
Mosaic of polarization angle around L5 point (white point) of the Earth-Moon system. The five rectangular windows correspond to the fields of view of the polarimetric imaging telescope with which the polarization diagrams of the Kordylewski dust cloud were measured. Image via J. Slíz-Balogh / RAS.
Judit Slíz-Balogh – who collaborated on this problem with other scientists and is the main author of one of the articles – commented:
Kordylewski's clouds are two of the most difficult objects to find. Although they are as close to Earth as the moon, they are largely ignored by astronomers. It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbor.
The SAR said:
Given their stability, points L4 and L5 are considered as potential sites for space probes in orbit and as transfer stations for missions exploring the wider solar system. It is also proposed to store pollutants at both locations.
Future research will focus on the L4 and L5 layers, as well as associated Kordylewski clouds, to understand their stability and determine if their dust poses a threat to equipment and future astronauts.
Kazimierz Kordylewski proposed the existence of Earth's dust cloud satellites in 1961, and astronomers have been arguing about them ever since. Have they now been confirmed? This 1964 image is via Wikimedia Commons.
In conclusion, researchers have confirmed the existence of Kordylewski dust clouds, which revolve around points L4 and L5 of the Earth-Moon system. In other words, clouds of dust gravitate around the lunar orbit. They move in front of and behind the moon in orbit.
Source n ° 1: Celestial mechanics and polarization optics of the Kordylewski dust cloud in the Lagrange point Earth-Moon L5 – Part I. Three-dimensional celestial mechanical modeling of the formation of dust clouds
Source n ° 2: Celestial mechanics and polarization optics of the Kordylewski dust cloud in the L5 Earth-Moon Lagrange point. Second part. Polarimetric observation imaging: new evidence of the existence of a Kordylewski dust cloud
Via RAS
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