Artist's illustration of the Kordylewski cloud in the night sky (with its brightness greatly enhanced) at the time of the observations.
Credit: G. Horváth
Posted on 11/07/2018 8:30:59 AM PST by ETL
Dust clouds that orbit Earth like moons may finally have had their existence confirmed after more than a half-century of controversy, new research finds.
In deep space, there are five points where the gravitational pull of Earth and the moon balance each other. Two of these so-called Lagrange points, L4 and L5, form an equal-sided triangle with Earth and the moon, and move around Earth as the moon orbits the planet. Any objects at either L4 or L5 can stay in relatively stable positions there about 239,000 miles (384,000 kilometers) from both Earth and the moon, barring any interference from the gravitational pulls of the sun and other bodies.
Lagrange points can exist between other pairs of bodies, and previous research detected more than a million asteroids at the sun-Jupiter L4 and L5 points, as well as the asteroid 2010 TK7 at the sun-Earth L4 point. Prior work also suggested that at the Earth-moon L5 point, two clouds of dust might exist, ones first reported by and named for Polish astronomer Kazimierz Kordylewski in 1961.
Now researchers suggest they may finally have confirmed that this pair of dust clouds is real. The scientists detailed their findings in two studies online Sept. 1 and Oct. 1 in the journal Monthly Notices of the Royal Astronomical Society.
The Kordylewski clouds are exceptionally faint, and whether one can see them with the naked eye or normal cameras depends heavily on the state of the weather.
As a result, many scientists have doubted their existence for decades, Gábor Horváth, a physicist at Eötvös Loránd University in Hungary and co-author on both studies, told Space.com.
The scientists first developed computer models of the Kordylewski clouds to see how they formed and how light scattered off or reflected by these clouds might be detected. They focused on a feature of this scattered or reflected light called polarization. All light waves can ripple up and down, left and right, or at any angle in between, and scattered or reflected light is typically polarized much the same way, depending on the angle of scattering or reflection.
The researchers next sought to detect the Kordylewski clouds using a digital camera at a private observatory in Hungary. The camera was equipped with polarizing filters that only let in light with specific polarizations.
"Now we find new observational evidence for the existence of the Kordylewski dust clouds around the L5 point of the Earth-moon system," Judit Slíz-Balogh, an astronomer at Eötvös Loránd University in Budapest and lead author of both studies, told Space.com.
Images of the purported location of a Kordylewski cloud revealed polarized light reflected from dust extending well outside the camera's field of view. This matches predictions the scientists made of how a Kordylewski cloud would look.
"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 neighbor."
In the future, scientists can see whether dust clouds also exist at the Earth-moon L4 point, Slíz-Balogh added.
Given the stability of the Earth-moon L4 and L5 points, they are often seen as potential sites for space stations. Future research into Kordylewski clouds may see how stable they are and whether their dust poses any potential threat to equipment and astronauts at the L4 and L5 points, the researchers said.
Kordylewski clouds are large concentrations of dust that exist at the L and L Lagrangian points of the Earth–Moon system.[1][2][3] They were first reported by Polish astronomer Kazimierz Kordylewski in the 1960s, and confirmed to exist in October 2018.[1][2][3]
Discovery and observation
The existence of a photometrically confirmable concentration of dust at the libration points was predicted by Josef Witkowski in 1956 (1951?).[4][5]
The clouds were first seen by Kordylewski in 1956.[6] Between 6 March and 6 April 1961, he succeeded in photographing two bright patches near the L libration point.[5] During the observation time, the patches hardly appeared to move relative to L.[5] The observations were taken from the mountain Kasprowy Wierch.[5]
In 1967, J. Wesley Simpson made observations of the clouds using the Kuiper Airborne Observatory.
In October 2018, the existence of the Kordylewski clouds was reported to have been confirmed,[1][2][3] even though, earlier, in 2009, the Japanese Hiten space probe, which passed through the libration points to detect trapped dust particles, did not find an obvious increase in dust levels above the density in surrounding space.[6][7]
Appearance
The Kordylewski clouds are a very faint phenomenon, comparable to the brightness of the gegenschein.[8]
They are very difficult to observe from Earth[6] but may be visible to the unaided eye in an exceptionally dark and clear night sky.[8] Most claimed observations have been made from deserts, at sea, or from mountains.[8] The clouds appear somewhat redder than the gegenschein, indicating that they may be made of a different kind of particle.[6]
The Kordylewski clouds are located near the L and L Lagrange points of the Earth–Moon system.[6] They are about 6 degrees in angular diameter.[6] The clouds can drift up to 6 to 10 degrees from those points.[8] Other observations suggest they move around the libration points in ellipses of about 6 by 2 degrees.[6]
Explanation:
Like the zodiacal light, the gegenschein is sunlight scattered by interplanetary dust.
Most of this dust is orbiting the Sun in about the ecliptic plane, with a possible concentration of particles at the L2 Earth–Sun Lagrangian point.[1]
It is distinguished from zodiacal light by its high angle of reflection of the incident sunlight on the dust particles.
It forms a slightly more luminous, oval glow directly opposite the Sun within the band of luminous zodiacal light.
The intensity of the gegenschein is relatively enhanced, because each dust particle is seen in full phase.[2]
History
The gegenschein was first described by the French Jesuit astronomer and professor Esprit Pezenas (fr) (1692–1776) in 1730.
Further observations were made by the German explorer Alexander von Humboldt during his South American journey from 1799 to 1803. It was also Humboldt who gave the phenomenon its German name Gegenschein.[3]
The Danish astronomer Theodor Brorsen published the first thorough investigations of the gegenschein in 1854,[4] stating that Pezenas was the first to see it. T. W. Backhouse discovered it independently in 1876, as did Edward Emerson Barnard in 1882.[5]
In modern times, the gegenschein is not visible in most inhabited regions of the world due to light pollution.
Sunlight scattered by interplanetary dust causes this phenomenon. Zodiacal light is best seen during twilight after sunset in spring and before sunrise in autumn, when the zodiac is at a steep angle to the horizon.
However, the glow is so faint that moonlight and/or light pollution outshine it, rendering it invisible.
The brightness of zodiacal light decreases with distance from the Sun. In naturally dark night skies, the glow is visible as a band along the entire zodiac, completely straddling the ecliptic.
In fact, zodiacal light spans the entire sky and largely[5] contributes to the total natural light in a clear and moonless night sky.
Another phenomenon – a faint but slightly brighter oval glow – directly opposite of the Sun’s direction is the gegenschein, which is caused by backscattered sunlight.
The interplanetary dust in the Solar System collectively forms a thick, pancake-shaped cloud called the zodiacal cloud, which straddles the ecliptic plane.
The particle sizes range between 10 and 300 micrometres, most with a mass around 150 micrograms.[6]
IOW, Earth has a ring....................
Interesting!
Pales in comparison to most other space phenomenon, but since it, like the other two referenced, apparently can be seen with the naked eye, I thought it worth posting.
How long before somebody stupid calls it “space pollution”?
Space dust bunny ping!
It IS space pollution!
Specially Zodiacal Light. If you are doing a Messier Marathon in March, trying to find M74 when it is already almost the same color as the sky, and, along comes Mr Zodiacal raising the light of the sky even further, so, M74 blends in to a point where you can’t see it, it’s pollution.
And, NO, I wasn’t using GOTO or digital setting circles. I was star hopping. (I have DSC now, but, not then)
There, I said it!
So now Algore is gonna work to get us to pay for cleaning it up?
No, I think Algore should have to go into space and clean it up himself...without a space suit.
Thanks ETL. Eureka moment! /rimshot
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