Claimed moons of Earth


Claims of the existence of other moons of Earth—that is, of one or more natural satellites with relatively stable orbits of Earth, other than the Moon —have existed for some time. Several candidates have been proposed, but none has been confirmed. Since the 19th century, scientists have made genuine searches for more moons, but the possibility has also been the subject of a number of dubious non-scientific speculations as well as a number of likely hoaxes.
Although the Moon is Earth's only natural satellite, there are a number of near-Earth objects with orbits that are in resonance with Earth. These have been called "second" moons of Earth.
, an asteroid discovered on 27 April 2016, is possibly the most stable quasi-satellite of Earth. As it orbits the Sun, 469219 Kamoʻoalewa appears to circle around Earth as well. It is too distant to be a true satellite of Earth, but is the best and most stable example of a quasi-satellite, a type of near-Earth object. They appear to orbit a point other than Earth itself, such as the orbital path of the NEO asteroid 3753 Cruithne. Earth trojans, such as, are NEOs that orbit the Sun on the same orbital path as Earth, and appear to lead or follow Earth along the same orbital path.
Other small natural objects in orbit around the Sun may enter orbit around Earth for a short amount of time, becoming temporary natural satellites., the only confirmed examples have been in Earth orbit during 2006 and 2007, and in Earth orbit between 2018 and 2020.

History

Petit's moon

The first major claim of another moon of Earth was made by French astronomer Frédéric Petit, director of the Toulouse Observatory, who in 1846 announced that he had discovered a second moon in an elliptical orbit around Earth.
It was claimed to have also been reported by Lebon and Dassier at Toulouse, and by Larivière at Artenac Observatory, during the early evening of March 21, 1846.
Petit proposed that this second moon had an elliptical orbit, a period of 2 hours 44 minutes, with apogee and perigee. This claim was soon dismissed by his peers. The perigee is similar to the cruising altitude of most modern airliners, and within Earth's atmosphere. Petit published another paper on his 1846 observations in 1861, basing the second moon's existence on perturbations in movements of the actual Moon. This second moon hypothesis was not confirmed either.
Petit's proposed moon became a plot point in Jules Verne's 1870 science fiction novel Around the Moon.

Waltemath's moons

In 1898 Hamburg scientist Dr. Georg Waltemath announced that he had located a system of tiny moons orbiting Earth. He had begun his search for secondary moons based on the hypothesis that something was gravitationally affecting the Moon's orbit.
Waltemath described one of the proposed moons as being from Earth, with a diameter of, a 119-day orbital period, and a 177-day synodic period. He also said it did not reflect enough sunlight to be observed without a telescope, unless viewed at certain times, and made several predictions of its next appearances. "Sometimes, it shines at night like the sun but only for an hour or so."
E. Stone Wiggins, a Canadian weather expert, ascribed the cold spring of 1907 to the effect of a second moon, which he said he had first seen in 1882 and had publicized the find in 1884 in the New-York Tribune when he put it forward as probable cause of an anomalous solar eclipse of May of that year. He said it was also probably the "green crescent moon" seen in New Zealand and later in North America in 1886, for periods of less than a half-hour each time. He said this was the "second moon" seen by Waltemath in 1898. Wiggins hypothesized that the second moon had a high carbon atmosphere but could be seen occasionally by its reflected light.
The existence of these objects put forward by Waltemath was discredited after the absence of corroborating observation by other members of the scientific community. Especially problematic was a failed prediction that they would be seen in February 1898.
The August 1898 issue of Science mentioned that Waltemath had sent the journal "an announcement of a third moon", which he termed a wahrhafter Wetter und Magnet Mond. It was supposedly in diameter, and closer than the "second moon" that he had seen previously.

Other claims

In 1918, astrologer Walter Gornold, also known as Sepharial, claimed to have confirmed the existence of Waltemath's moon. He named it Lilith. Sepharial claimed that Lilith was a 'dark' moon invisible for most of the time, but he claimed to be the first person in history to view it as it crossed the Sun.
In 1926 the science journal Die Sterne published the findings of amateur German astronomer W. Spill, who claimed to have successfully viewed a second moon orbiting Earth.
In the late 1960s John Bagby claimed to have observed over ten small natural satellites of Earth, but this was not confirmed.

General surveys

studied the possibility of a second moon and made a general search ruling out the possibility of many types of objects by 1903. His 1922 article "A Meteoritic Satellite" in Popular Astronomy resulted in increased searches for small natural satellites by amateur astronomers. Pickering had also proposed the Moon itself had broken off from Earth.
In early 1954 the United States Army's Office of Ordnance Research commissioned Clyde Tombaugh, discoverer of Pluto, to search for near-Earth asteroids. The Army issued a public statement to explain the rationale for this survey. Donald Keyhoe, who was later director of the National Investigations Committee on Aerial Phenomena, a UFO research group, said that his Pentagon source had told him that the actual reason for the quickly initiated search was that two near-Earth objects had been picked up on new long-range radar in mid-1953. In May 1954, Keyhoe asserted that the search had been successful, and either one or two objects had been found. At The Pentagon, a general who heard the news reportedly asked whether the satellites were natural or artificial. Tombaugh denied the alleged discovery in a letter to Willy Ley, and the October 1955 issue of Popular Mechanics magazine reported:
At a meteor conference in Los Angeles in 1957, Tombaugh reiterated that his four-year search for natural satellites had been unsuccessful. In 1959, he issued a final report stating that nothing had been found in his search.

Modern status

It was discovered that small bodies can be temporarily captured, as shown by, which was in Earth orbit in 2006–2007.
In 2010, the first known Earth trojan was discovered in data from Wide-field Infrared Survey Explorer, and is currently called.
In 2011, planetary scientists Erik Asphaug and Martin Jutzi proposed a model in which a second moon would have existed 4.5 billion years ago, and later impacted the Moon, as a part of the accretion process in the formation of the Moon.
In 2018, it was confirmed two dust clouds orbited Earth at the Moon's, known as the Kordylewski clouds. These were nicknamed "Earth's hidden moons".
The interpretation of some bodies has led to sometimes bold statements in the astronomy press, though often allowing for other interpretations:

Quasi-satellites and trojans

Although no other moons of Earth have been found to date, there are various types of near-Earth objects in 1:1 resonance with it, which are known as quasi-satellites. Quasi-satellites orbit the Sun from the same distance as a planet, rather than the planet itself. Their orbits are unstable, and will fall into other resonances or be kicked into other orbits over thousands of years. Quasi-satellites of Earth include,,
,,,,
and 3753 Cruithne. Cruithne, discovered in 1986, orbits the Sun in an elliptical orbit but appears to have a horseshoe orbit when viewed from Earth. Some went as far to nickname Cruithne "Earth's second moon".
The key difference between a satellite and a quasi-satellite is that the orbit of a satellite of Earth fundamentally depends on the gravity of the Earth–Moon system, whereas the orbit of a quasi-satellite would negligibly change if Earth and the Moon were suddenly removed because a quasi-satellite is orbiting the Sun on an Earth-like orbit in the vicinity of Earth.
Earth possesses one known trojan, a small Solar System body caught in the planet's gravitationally stable Lagrangian point. This object,, is roughly 300 metres across. Like quasi-satellites, it orbits the Sun in a 1:1 resonance with Earth, rather than Earth itself.
NameEccentricityDiameter
DiscovererYear of discoveryTypeCurrent typeDate Ejected/Destroyed
Moon0.0553474800??Natural satelliteNatural satelliteN/A
1913 Great Meteor Procession???1913 February 9Possible Temporary satelliteDestroyed1913 February 9
3753 Cruithne0.5155000Duncan Waldron1986 October 10Quasi-satelliteHorseshoe orbitN/A
0.0535–12Spacewatch1991 November 6Temporary satelliteApollo asteroidN/A
0.345210–470Lincoln Lab's ETS1998 October 18Horseshoe orbitHorseshoe orbit?
54509 YORP0.230124Lincoln Lab's ETS2000 August 3Horseshoe orbitHorseshoe orbitN/A
0.16835–85Lincoln Lab's ETS2001 April 13Possible Horseshoe orbitPossible Horseshoe orbit7 January 2002*
0.01320–100LINEAR2002 January 9Quasi-satelliteHorseshoe orbitN/A
0.01410–30LINEAR2003 December 20Quasi-satelliteHorseshoe orbitN/A
0.136160–360LINEAR2004 April 13Quasi-satelliteQuasi-satellite~Y2600
0.377140–320Spacewatch2006 March 29Quasi-satelliteQuasi-satelliteN/A
0.0836–13Catalina Sky Survey2006 May 6Horseshoe orbitHorseshoe orbit?
0.0242–3Catalina Sky Survey2006 September 14Temporary satelliteApollo asteroidN/A
0.075357WISE2010 September 17Horseshoe orbitHorseshoe orbitN/A
0.191150–500WISE2010 October 1Earth trojanEarth trojanN/A
0.08320–40Spacewatch2013 January 20Horseshoe orbitHorseshoe orbitN/A
0.452130–300Pan-STARRS2013 June 12Quasi-satellite temporaryQuasi-satellite temporary?
0.461170EURONEAR2014 July 29Quasi-satellite temporaryQuasi-satellite temporary~Y2185
0.10850–111Črni Vrh Observatory2015 September 21Quasi-satelliteHorseshoe orbit temporary?
0.1849–22Mount Lemmon Survey2015 December 9Horseshoe orbit temporaryHorseshoe orbit temporary?
0.2799–22Catalina Sky Survey2015 December 16Horseshoe orbit temporaryHorseshoe orbit temporary?
0.4047–16Mount Lemmon Survey2015 December 19Horseshoe orbit temporaryHorseshoe orbit temporary?
469219 Kamoʻoalewa0.10441-100Pan-STARRS2016 April 27Quasi-satellite stableQuasi-satellite stableN/A
DN160822 03???2016 August 22Possible Temporary satelliteDestroyed22 August 2016
0.0171–6Mount Lemmon Survey2020 February 15Temporary satelliteTemporary satellite ~May 2020

Temporary satellites

Computer models by astrophysicists Mikael Granvik, Jeremie Vaubaillon, and Robert Jedicke suggest that these "temporary satellites" should be quite common; and that "At any given time, there should be at least one natural Earth satellite of 1 meter diameter orbiting the Earth." Such objects would remain in orbit for ten months on average, before returning to solar orbit once more, and so would make relatively easy targets for manned space exploration. "Mini-moons" were further examined in a study published in the journal Icarus.
It has been proposed that NASA search for temporary natural satellites, and use them for a sample return mission.

1913

The earliest known mention in the scientific literature of a temporarily captured orbiter is by Clarence Chant about the Meteor procession of 9 February 1913:
Later, in 1916, William Frederick Denning surmised that:

2006

On 14 September 2006, an object estimated at 5 meters in diameter was discovered in near-polar orbit around Earth. Originally thought to be a third-stage Saturn S-IVB booster from Apollo 12, it was later determined to be an asteroid and designated as. The asteroid re-entered solar orbit after 13 months and is expected to return to Earth orbit after 21 years.

2015

In April 2015, an object was discovered orbiting the Earth, and initially designated, but more detailed investigation quickly showed the object to be the Gaia spacecraft, and the object's discovery soon was retracted.
On 3 October 2015, a small object, temporarily designated WT1190F, was found to be orbiting the Earth every ~23 days, and had been orbiting since at least late 2009. It impacted the Earth on 13 November 2015 at 06:18:34.3 UTC.

2016

On 8 February 2016 an object ~0.5 meter in diameter was discovered orbiting the Earth with a period of 5 days and given the temporary designation XC83E0D, and most likely lost. The object was later identified as the lost artificial satellite SR-11A, or possibly its companion SR-11B, which were launched in 1976 and lost in 1979.
On 8 April 2016, an object, given the temporary designation S509356, was discovered with an orbital period of 3.58 days. Although it has the typical area-to-mass ratio of satellites, it has a color typical of S-type asteroids. It was later identified as the Yuanzheng-1 stage from the launch of Chinese navigation satellites.

2017

On 8 December 2017, the object YX205B9 was discovered with an orbital period of 21 days, on an eccentric orbit taking it from slightly beyond the geocentric satellite ring to almost twice the distance of the Moon. It was later identified as the booster stage from the Chang'e 2 mission.

2018-2020

was discovered in 2020, and seems to have been orbiting Earth since 2018.

Literature