from
https://www.nbcnews.com/mach/science...rth-ncna930031

(Either this piece is sci-fi, or it discusses what plenty
of sci-fi talks about = Lagrange points.)

'Ghost moons' discovered in orbit around Earth

The moonlike dust clouds were first detected decades ago, but now
astronomers have solid evidence that they're real.
Image: Dust moon
They may not look like moons, but these dust clouds orbit Earth at
roughly the same distance.J. Sl?z-Balogh / Royal Astronomical Society
Nov. 2, 2018 / 1:39 AM PDT
By Shoshana Wodinsky
Everyone knows Earth has only one moon — or is it three? Astronomers in
Hungary say they’ve detected a pair of what some call “ghost moons”
orbiting our planet not far from the moon we all know.

The hazy clouds of dust — tens of thousands of miles across but too
faint to be seen with the naked eye — were first detected almost 60
years ago by a Polish astronomer, Kazimierz Kordylewski. But the patches
of light he found were too indistinct to convince some scientists that
the clouds were really there, and the existence of the "Kordylewski
clouds" has long been a matter of controversy.

Now the astronomers, Gabor Horvath and Judit Sliz-Balogh of Eötvös
Loránd University in Budapest, have obtained clear evidence of the
clouds using a specially equipped telescope in a private observatory in
western Hungary.

In the new images, published Oct. 2 in the journal Monthly Notices of
the Royal Astronomical Society, the so-called Kordylewski clouds appear
as indistinct patches of light against the darkness of space — though
they show up clearly in an artist's rendering that greatly exaggerates
their brightness.

Image: Dust moonArtist's impression of the Kordylewski cloud in the
night sky (with its brightness greatly enhanced) at the time of the
observations.G. Horv?th / Royal Astronomical Society
“Think of them like the cloud of dust you get when a car drives down a
dirt road,” astronomer Phillip Plait, who writes the popular Bad
Astronomy blog, told NBC News MACH in an email. “So they're not really
'moons' in the usual sense.”

The Kordylewski clouds orbit Earth at roughly the same distance as the
moon — about 250,000 miles away. One cloud orbits ahead of the moon and
the other behind in specific regions of the sky where Earth's
gravitational pull is canceled out by the moon's. Known as Lagrange
points, these regions act as “gravitational vacuum-cleaners,” collecting
dust and gas that can persist for decades, Horvath said in an email.

“The idea here is that when you have a biggish object, like the Earth,
orbited by a smaller one, like the moon, there are regions of space
where the centrifugal force balances gravity,” Plait said. “Put a much
smaller object there, and it'll stay there for a long time.”

Just how long remains uncertain. Though the clouds seem to have been in
existence at least since 1961, when Kordylewski first detected them,
some researchers say these dusty clouds could dissipate in coming years.
As Miki Nakajima, a planetary scientist at the University of Rochester,
put it, "These clouds are transient."

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