Cruithne – Strange And Fascinating Celestial Body Dancing Back And Forth

A. Sutherland – MessageToEagle.com – Except for the Moon, our planet has also another celestial companion in its vicinity. The object’s name is Cruithne (or 3753 Cruithne) often called Earth’s “second moon”. One orbit of Cruithne takes almost a year (orbital period: 364.019 days) similar to the Earth and the Moon.

Based on astronomical calculations, Cruithne has probably been synchronized with Earth’s orbit for a long time. There is no danger of a collision with Earth for millions of years, if ever. Its orbital path and Earth’s do not cross.

Currently, its orbital plane is tilted to that of the Earth by 19.8°.

The orbits of Cruithne and Earth over the course of a year (from September 2007 to August 2008). Cruithne's location is indicated by the red box as it is too small to be seen at this distance. Earth is the white dot moving along the blue circle. The yellow circle in the centre is our Sun.
The orbits of Cruithne and Earth over the course of a year (from September 2007 to August 2008). Cruithne’s location is indicated by the red box as it is too small to be seen at this distance. Earth is the white dot moving along the blue circle. The yellow circle in the center is our Sun.

Cruithne is an asteroid with a diameter of about 5 km (3 miles) and a horseshoe-like path. When observed from a point above the north pole of the earth the asteroid Cruithne follows a very complex horseshoe orbit.

This is not an elliptical or circular shape of orbit typical for our Solar System, but nothing related to Cruithne is typical.

With respect to our planet, Cruithne’s movements are very slow.

At particular points in its orbit, Cruithne suddenly reverses its rate of motion giving an impression of “dancing” back and forth. Cruithne has been known for a very long time but not officially.

According to ancient Celtic lore, the Cruithne were “the first Celtic racio-tribal group to come to the British Isles, appearing between about 800 and 500 B.C. and coming from the European continent.

They were also known as the Picts. Cruithne was also the name of a legendary king of the Picts, who had seven sons.

Officially, this one of the most peculiar celestial objects of our Solar System was discovered by J. Duncan Waldron at Siding Spring Observatory, Coonabarabran, Australia on October 10, 1986, while searching for NEOs (Near Earth Objects).

Most of the known asteroids are in orbit around the Sun but somewhere between the orbits of Mars and Jupiter. Some of them are circulating closer to our home star while the others have their orbits farther out.

See also:

Cruithne Asteroid With Unusual Orbit Discovered – On October 10, 1986

Cruithne: Legendary King, His Seven Sons And The First Celtic Tribe That Inhabited British Isles

Cruithne has its orbit very close to Earth and it is considered as a close companion not only to the Moon but also Earth. The asteroid does not go around the Earth, instead, it shares the Earth’s orbit.

Cruithne's specific path
Cruithne’s specific path

It was discovered on October 10, 1986, by Duncan Waldron on a photographic plate taken with the UK Schmidt Telescope at Siding Spring Observatory, Coonabarabran, Australia.

The 1983 apparition (1983 UH) is credited to Giovanni de Sanctis and Richard M. West of the European Southern Observatory in Chile.

Cruithne’s weird orbit was first determined in 1997 by three astronomers Paul Wiegert, Kimmo Innanen at York University in Toronto, and Seppo Mikkola, working at the University of Turku in Finland.

The asteroid has a very special relationship with our planet and a collision with Earth is not possible. This small object is in orbit around the Sun and at a distance very close to that of the Earth.

Horseshoe_orbit_of_Cruithne_from_the_perspective_of_Earth
Cruithne appears to make a bean-shaped orbit from the perspective of Earth. Credit: Wikipedia

Cruithne comes closer to Earth at a distance of about 15 million kilometers (9.3 million miles).

It means forty times that of the Moon. As observed today, Cruithne’s present trajectory is seriously dominated by Earth’s gravity, and this state will remain for about 5,000 years.

What will happen later?

Well, this relationship is certainly not forever and Cruithne will eventually escape one day in the future.

 

Cruithne's orbit -Animation credits: Paul Wiegert
Cruithne’s orbit -Animation
credits: Paul Wiegert

Of course, our small asteroid Cruithne with its “dance”-like path, is not alone in the Solar System.

Similar behavior has Janus, the 10th largest moon of Saturn and its 12th largest moon known as Epimetheus.

Both two occupy almost the same orbit (within 50 kilometers or 30 miles of each other).

Each year Cruithne’s orbit drifts around the sun relative to earth

Cruithne’s orbit relative to earth drifts around, after 190 years it circles the earth from the other side.

Mars has also a small companion known as Eureka (or 5261 Eureka) with a behavior similar to that of Cruithne.

Eureka is the first known so-called Mars Trojan asteroid. (Trojan asteroids, a group of objects sharing the orbit of Jupiter.

However similar planetoidal bodies have also been found sharing the orbits of Mars and Neptune.

Mars Trojan, Eureka has its location on Mars orbit at the distance of approximately 60° behind Mars. Jupiter has also probably a few hundred planetoids acting similar to the fascinating Cruithne.

Written by – A. Sutherland  – MessageToEagle.com Senior Staff Writer

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