3753 Cruithne
| Orbital characteristics | |
|---|---|
| Orbit type | Near-Earth |
| Semimajor axis | 0.99778 AU |
| Eccentricity | 0.514784 |
| Orbital period | 365d 6h |
| Inclination | 19.8122° |
| Physical characteristics | |
| Diameter | 5 km |
| Mass | ? kg |
| Density | ? g/cm3 |
| Rotation period | ? |
| Spectral class | ? |
| Albedo | ? |
| History | |
| Discoverer | various, 1986 |
3753 Cruithnean asteroid withcatalogue number 3753 thatcurrentlyan unusual orbit relatedthatEarth. It was officially discovered on October 10, 1986, by D. Waldron, workingR. McNaught, M. HartleyM. Hawkins at Siding Spring Observatory, Coonabarabran, Australia. However, its unusual orbit was not determined until 1997 by Paul WiegertKimmo Innanen, working at York UniversityCanada,Seppo Mikkola, working atUniversityTurkuFinland.
The Dalriada Celtic Heritage Trust inform usCruithne werefirst Celtic racio-tribal groupcome toBritish Isles, appearing between about 800500 B.C.,coming fromEuropean continent. They were also known asPicts.[1] The correct pronunciation'Cruithne''croo-ee-nya'. The emphasis should be on'croo'.
Cruithne shares Earth's orbit, but does not actually orbitEarth. Instead,followsspiralling path that moves alongEarth's orbit inhorseshoe shape,two ends ofhorseshoe approaching either sideEarth but not quite reaching it. It takes Cruithne 385 Earth yearscomplete one such horseshoe orbit. This orbital path appears extremely complexnon-intuitive when viewed from Earth's framereference. Itmuch easierunderstand by recognizing that fromSun's framereference Cruithne followsrelatively conventional orbit which takes almost exactlysame timecomplete as Earth's (one year), but whichslightly more elliptical. The gravitational influenceEarth modifies this elliptical orbit only slightly, just enoughmodify Cruithne's precessionpreventfrom coming too close.
Cruithneapproximately 5 kmdiameter,its closest approachEarth15 million kilometers (approximately 40 timesseparation between EarthLuna). Although Cruithne's orbitnot thoughtbe stable overlong term, thereno dangerit colliding withEarthany forseeable future. Cruithnenot visible tonaked eye at any pointits orbit.
Thereonly one other known examplenatural bodies inhorseshoe orbit attimewriting,natural satellitesSaturn named JanusEpimetheus. The orbit these two moons follow around Saturnmuch simpler thanone Cruithne follows, but operates alongsame general principles.
Mars has one co-orbital asteroid (its name5261 Eureka),Jupiter has many (about 400 objects,Trojan asteroids); therealso other small co-orbital moons inSaturnian system: TelestoCalypsoTethys,HeleneDione. However, nonethese follow horseshoe orbits.
External link
- For more detailed information on Cruithne's unusual orbit, see: http://www.astro.queensu.ca/~wiegert/3753/3753.html
- For java-applet based animations showing Cruithne's orbit, see: http://burtleburtle.net/bob/physics/cruithne.html
