{ "id": "epxbzgdndp", "slug": "501-urhixidur", "title": "501 Urhixidur", "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-main-belt", "label": "Main-belt asteroids and numbered minor planets", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-main-belt" }, { "id": "places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids", "label": "Outer-belt asteroids", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids" }, { "id": "places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig", "label": "Asteroids named for literary and allegorical figures", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig" } ], "geo": [ { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig", "label": "Non-geographic · Not dated: Asteroids named for literary and allegorical figures", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig", "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-main-belt", "label": "Main-belt asteroids and numbered minor planets", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt" }, { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids", "label": "Outer-belt asteroids", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids" }, { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig", "label": "Asteroids named for literary and allegorical figures", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig" } ] } ], "excerpt": "501 Urhixidur (1903 LB, A903 BK) is a 74.5-km main-belt asteroid discovered by Max Wolf at Heidelberg on 18 January 1903; it orbits the Sun every 5.61 years and rotates in 13.17 hours.", "snippet": "501 Urhixidur (1903 LB, A903 BK) is a 74.5-km main-belt asteroid discovered by Max Wolf at Heidelberg on 18 January 1903; it orbits the Sun every 5.61 years and rotates in 13.17 hours.", "node": "places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroids-named-for-literary-and-allegorical-fig", "markdown": "# 501 Urhixidur\n\n**501 Urhixidur** (provisional designation 1903 LB, also A903 BK) is a large main-belt asteroid orbiting between Mars and Jupiter, about 74.5 kilometers in diameter, discovered by [Max Wolf](https://www.edgepedia.org/max-wolf) on 18 January 1903 at [Heidelberg](https://www.edgepedia.org/heidelberg).[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) • [2](https://www.le-systeme-solaire.net/astero501.html) It is not classified as a near-Earth object or as potentially hazardous, because its orbit stays well away from Earth's.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk)\n\n| Key fact | Detail |\n|---|---|\n| Discovery | 18 January 1903, Heidelberg, by M. F. Wolf[2](https://www.le-systeme-solaire.net/astero501.html) |\n| Class | Main-belt asteroid; not a near-Earth object and not potentially hazardous[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n| Diameter | 74.46 km, with albedo 0.052[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n| Orbit | Semi-major axis 3.162 AU, eccentricity 0.1417, inclination 20.84 degrees[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n| Orbital period | 2,050 days (5.61 years), from 2.71 AU at perihelion to 3.61 AU at aphelion[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n| Rotation | 13.17 hours per rotation[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n| Observational record | 8,241 Minor Planet Center observations used for its orbit, spanning 1903 to 2023[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) |\n\n## Discovery\n\nThe asteroid was found on 18 January 1903 at Heidelberg by the German astronomer Max Wolf (M. F. Wolf), who in the same weeks discovered several neighboring numbered asteroids, including [502 Sigune](https://www.edgepedia.org/502-sigune) on 19 January 1903.[2](https://www.le-systeme-solaire.net/astero501.html) A French summary of discovery circumstances likewise credits Max Wolf with the find on 18 January 1903 at the Königstuhl Observatory of Heidelberg, Germany.[3](https://www.techno-science.net/fr/definitions/501-urhixidur)\n\n## Orbit\n\nUrhixidur orbits the Sun every 2,050 days, or 5.61 years, coming as close as 2.71 AU and reaching as far as 3.61 AU, on a semi-major axis of 3.162 AU with eccentricity 0.1417 and an inclination of 20.84 degrees to the ecliptic.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) Its average orbital speed is 16.78 km/s.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk)\n\n**No close approaches to Earth.** The closest point of its orbit lies 1.71 AU from [Earth's orbit](https://www.edgepedia.org/earths-orbit), and orbital simulations conducted by NASA JPL's CNEOS show no close approaches to Earth; JPL has therefore not classified Urhixidur as potentially hazardous.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) The asteroid is also not considered a viable target for human exploration by the NHATS study.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk)\n\nThe orbit is well determined. The [Minor Planet Center](https://www.edgepedia.org/minor-planet-center) records 8,241 observations used to determine it, with observations dating back to 18 January 1903 and a last official observation on 30 June 2023.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) A Czech asteroid data page lists 8,606 observations across 56 oppositions, observed from 1903 onward, with an absolute magnitude H of 9.47 mag and a [Tisserand parameter](https://www.edgepedia.org/tisserand-parameter) with respect to Jupiter of 3.1.[4](https://astronomia.zcu.cz/planety/planetka-501)\n\n## Physical properties\n\nUrhixidur is about 74.5 kilometers in diameter, a size the Space Reference summary describes as larger than 99 percent of asteroids and comparable to the U.S. state of Delaware, with a geometric albedo of 0.052, a dark surface typical of many outer-belt asteroids.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk)\n\n**Slow rotation.** The asteroid completes one rotation on its axis every 13.17 hours.[1](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk) A study of slowly rotating asteroids by A. Marciniak and colleagues ([Astronomy & Astrophysics](https://www.edgepedia.org/astronomy-and-astrophysics), 654, A87, 2021) presents composite light curves of (501) Urhixidur built from ground-based photometry at CTIO and OASI together with TESS data from 2017 and 2018, giving a period of about 13.18 hours.[5](https://www.aanda.org/articles/aa/pdf/2021/10/aa40991-21.pdf) The DAMIT database of asteroid shape models carries a Urhixidur model with a sidereal period of 13.17203 hours and an albedo of 0.051.[6](https://damit.cuni.cz/projects/damit/asteroid_models/index/sort%3Athermal_inertia_min/direction%3Adesc/page%3A322)\n\n## Occultations\n\nBecause the asteroid is large and dark, stellar occultations, in which it briefly blocks the light of a background star, have been used to probe its size and shape. On 3 August 2006 UT, (501) Urhixidur, given there as 77 km in diameter, was predicted to occult an 11.8-magnitude star in the constellation Lupus along a path that could graze the southwestern end of New Zealand's South Island; the combined light of asteroid and star was expected to drop by 2.7 magnitudes to 14.4 for at most 7.5 seconds.[7](https://www.occultations.org.nz/planet/2006/updates/060803_501_5365_u.htm) Further occultation campaigns followed, including a predicted event on 8 October 2025 against the star UCAC4 681-044643, for which two positive video observations with GPS timing were recorded, with reported occultation durations of 4.80 and 5.40 seconds.[8](https://astro.kretlow.de/cora/events/sodis/2025-10-08/UCAC4%20681-044643/%28501%29%20Urhixidur/)\n\n## References\n\n1. [Asteroid Urhixidur, Space Reference](https://www.spacereference.org/asteroid/501-urhixidur-a903-bk)\n2. [Liste des astéroïdes du n°501 au n°1000, Le Système Solaire](https://www.le-systeme-solaire.net/astero501.html)\n3. [(501) Urhixidur, Techno-Science](https://www.techno-science.net/fr/definitions/501-urhixidur)\n4. [Planetka Urhixidur, Planety (Czech)](https://astronomia.zcu.cz/planety/planetka-501)\n5. [A. Marciniak et al. (2021). Properties of slowly rotating asteroids from CITPM. Astronomy & Astrophysics 654, A87](https://www.aanda.org/articles/aa/pdf/2021/10/aa40991-21.pdf)\n6. [DAMIT: Database of Asteroid Models from Inversion Techniques, (501) Urhixidur entry](https://damit.cuni.cz/projects/damit/asteroid_models/index/sort%3Athermal_inertia_min/direction%3Adesc/page%3A322)\n7. [RASNZ Occultation Section: Urhixidur occultation update, 2006 Aug 03](https://www.occultations.org.nz/planet/2006/updates/060803_501_5365_u.htm)\n8. [Cora Occultation: 2025-10-08 / UCAC4 681-044643 / (501) Urhixidur](https://astro.kretlow.de/cora/events/sodis/2025-10-08/UCAC4%20681-044643/%28501%29%20Urhixidur/)\n\n---\n*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Main-belt asteroids and numbered minor planets › Outer-belt asteroids › Asteroids named for literary and allegorical figures*\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/501-urhixidur", "markdown_url": "https://www.edgepedia.org/501-urhixidur.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": "\"501 Urhixidur\", Edgepedia (EdgeChat), https://www.edgepedia.org/501-urhixidur. Edgepedia Community License 1.0.", "credit_md": "\"[501 Urhixidur](https://www.edgepedia.org/501-urhixidur)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/501-urhixidur](https://www.edgepedia.org/501-urhixidur). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"501 Urhixidur\", Edgepedia (EdgeChat), https://www.edgepedia.org/501-urhixidur. Edgepedia Community License 1.0.", "speakable": "501 Urhixidur is a 74.5-km main-belt asteroid discovered by Max Wolf at Heidelberg on 18 January 1903; it orbits the Sun every 5.61 years and rotates in 13.17 hours." }