{ "id": "ep0g12781j", "slug": "5511-cloanthus", "title": "5511 Cloanthus", "updated": "2026-10-25", "topic_path": [ { "id": "places", "label": "Places and geography", "api_url": "https://www.edgepedia.org/api/v1/topics/places" }, { "id": "places.extraterrestrial", "label": "Extraterrestrial places", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial" }, { "id": "places.extraterrestrial.small-bodies", "label": "Small bodies of the Solar System", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies" }, { "id": "places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups", "label": "Jupiter Trojans and other dynamical groups", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups" }, { "id": "places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans", "label": "Trojan-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans" } ], "geo": [ { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans", "label": "Non-geographic · Not dated: Trojan-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.nodate", "label": "Non-geographic · Not dated", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate" }, { "id": "geo.nongeo.nodate.places", "label": "Places and geography", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places" }, { "id": "geo.nongeo.nodate.places.extraterrestrial", "label": "Extraterrestrial places", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial" }, { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies", "label": "Small bodies of the Solar System", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies" }, { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups", "label": "Jupiter Trojans and other dynamical groups", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups" }, { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans", "label": "Trojan-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans" } ] } ], "excerpt": "5511 Cloanthus is a large Jupiter Trojan asteroid about 40 kilometers wide with a slow, tumbling 336-hour rotation, never coming near Earth's orbit and not classified as potentially hazardous.", "snippet": "5511 Cloanthus is a large Jupiter Trojan asteroid about 40 kilometers wide with a slow, tumbling 336-hour rotation, never coming near Earth's orbit and not classified as potentially hazardous.", "node": "places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.trojan-camp-jupiter-trojans", "markdown": "# 5511 Cloanthus\n\n**5511 Cloanthus** (provisional designation 1988 TH1) is a large Jupiter Trojan asteroid, one of the bodies trapped in a 1:1 mean-motion resonance with Jupiter near its L4 and L5 Lagrangian points.\n\n| Key fact | Detail |\n|---|---|\n| Orbit | Semi-major axis 5.255 AU, eccentricity 0.119, inclination 11.17°; period 4,400 days (12.05 years)[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) |\n| Distance range | Perihelion 4.63 AU, aphelion 5.88 AU from the Sun[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) |\n| Rotation | 336.00 hours per revolution, a slow, tumbling (non-principal-axis) rotation[2](https://iaaras.ru/html/emp2021/emp_2021/parcur21d.pdf) |\n| Hazard status | Not a near-Earth object and not classified as potentially hazardous; its orbit stays 3.63 AU from Earth's orbit at the closest point[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) |\n\n## Orbit and dynamical setting\n\n[Jupiter Trojans](https://www.edgepedia.org/jupiter-trojans) follow essentially the same orbit as Jupiter, leading or trailing the planet by about 60 degrees in co-orbital motion.[3](https://www.nature.com/articles/nature03540) Cloanthus fits this pattern with a semi-major axis of 5.255 AU, close to Jupiter's own 5.2 AU, and an orbital period of 4,400 days, or 12.05 years.[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) Its eccentricity of 0.119 carries it from 4.63 AU at perihelion to 5.88 AU at aphelion, and its orbit is inclined 11.17 degrees to the ecliptic.[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1)\n\nThe orbit is well determined. Observations used for its orbit solution extend back to a precovery from July 30, 1951, and the [Minor Planet Center](https://www.edgepedia.org/minor-planet-center) records 3,135 observations, with the last official observation on July 3, 2023.[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) A Czech astronomical database lists 4,831 observations across 35 oppositions, observed from 1951 onward.[4](https://astronomia.zcu.cz/planety/planetka-5511)\n\nBecause the orbit never approaches [Earth's orbit](https://www.edgepedia.org/earths-orbit) closer than 3.63 AU, JPL's CNEOS simulations show no close approaches, and the asteroid is not classified as potentially hazardous. It is also not considered a viable target for human exploration by the NHATS study.[1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1)\n\n## Physical properties\n\nThe two estimates bracket the true size, which depends on how reflective the surface actually is.\n\nRotation is unusually slow. Photometric monitoring gives a rotation period of 336.00 hours, about 14 Earth days, and the asteroid is cataloged as a tumbling body rotating in non-principal-axis rotation rather than about a single fixed axis.[2](https://iaaras.ru/html/emp2021/emp_2021/parcur21d.pdf) • [1](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1) Slow, complex rotation of this kind is found among a subset of larger asteroids and is consistent with the long rotation periods reported for many Jupiter Trojans.[5](https://doi.org/10.1007/s11214-024-01052-7)\n\nTrojans as a population are thought to be more primitive than main-belt asteroids, believed to have formed at a range of heliocentric distances in the trans-Neptunian region, been scattered inward, and been captured during giant planet migration.[5](https://doi.org/10.1007/s11214-024-01052-7) Cloanthus shares this origin story with the rest of the Trojan clouds.\n\n## Occultations and observation opportunities\n\nBecause Cloanthus is large and its orbit is well known, it occasionally occults background stars. On 2019 May 3 UT, the roughly 40 km asteroid occulted a magnitude 12.1 star in the constellation Virgo for observers along a narrow path across northern [Queensland](https://www.edgepedia.org/queensland) and the Northern Territory of Australia; at that time the asteroid was 4.41 AU from Earth.[6](https://www.occultations.org.nz/planet/2019/updates/190503_5511_59986_u.htm) Stellar occultations by Trojans are used to constrain sizes and shapes beyond what photometry alone provides.\n\n## References\n\n1. [Asteroid Cloanthus (5511), Space Reference](https://www.spacereference.org/asteroid/5511-cloanthus-1988-th1)\n2. [Non-principal axis rotation (tumbling) asteroids table, IAA RAS](https://iaaras.ru/html/emp2021/emp_2021/parcur21d.pdf)\n3. [Morbidelli et al. (2005). Chaotic capture of Jupiter's Trojan asteroids in the early Solar System. Nature 435, 462–465.](https://www.nature.com/articles/nature03540)\n4. [Planetka Cloanthus (5511), Astronomia ZČU](https://astronomia.zcu.cz/planety/planetka-5511)\n5. [Mottola et al. (2024). Shapes, Rotations, Photometric and Internal Properties of Jupiter Trojans. Space Science Reviews 220, 17.](https://doi.org/10.1007/s11214-024-01052-7)\n6. [RASNZ Occultation Section: Cloanthus Occultation Update, 2019 May 3](https://www.occultations.org.nz/planet/2019/updates/190503_5511_59986_u.htm)\n\n---\n*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Jupiter Trojans and other dynamical groups › Trojan-camp Jupiter Trojans*\n\n*Initially written Oct 21, 2026 · Edited: Oct 25, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/5511-cloanthus", "markdown_url": "https://www.edgepedia.org/5511-cloanthus.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"5511 Cloanthus\", Edgepedia (EdgeChat), https://www.edgepedia.org/5511-cloanthus. Edgepedia Community License 1.0.", "credit_md": "\"[5511 Cloanthus](https://www.edgepedia.org/5511-cloanthus)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/5511-cloanthus](https://www.edgepedia.org/5511-cloanthus). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"5511 Cloanthus\", Edgepedia (EdgeChat), https://www.edgepedia.org/5511-cloanthus. Edgepedia Community License 1.0.", "speakable": "5511 Cloanthus is a large Jupiter Trojan asteroid about 40 kilometers wide with a slow, tumbling 336-hour rotation, never coming near Earth's orbit and not classified as potentially hazardous." }