{ "id": "ep8adppn2a", "slug": "780-armenia", "title": "780 Armenia", "updated": "2026-10-21", "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.asteroid-families-of-the-outer-belt", "label": "Asteroid families of the outer belt", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroid-families-of-the-outer-belt" } ], "geo": [ { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroid-families-of-the-outer-belt", "label": "Non-geographic · Not dated: Asteroid families of the outer belt", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroid-families-of-the-outer-belt", "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.asteroid-families-of-the-outer-belt", "label": "Asteroid families of the outer belt", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroid-families-of-the-outer-belt" } ] } ], "excerpt": "780 Armenia, main-belt asteroid, namesake of the compact high-inclination Armenia family. Dark (albedo 0.038), ~100 km diameter, slow 19.88-hour rotation, X-complex/T-type taxonomy, semimajor axis 3.11 AU.", "snippet": "780 Armenia, main-belt asteroid, namesake of the compact high-inclination Armenia family. Dark (albedo 0.038), ~100 km diameter, slow 19.88-hour rotation, X-complex/T-type taxonomy, semimajor axis 3.11 AU.", "node": "places.extraterrestrial.small-bodies.asteroids-main-belt.outer-belt-asteroids.asteroid-families-of-the-outer-belt", "markdown": "# 780 Armenia\n\n**780 Armenia** is a large, dark main-belt asteroid, the lowest-numbered member and namesake of a small, compact, high-inclination asteroid family in the outer main belt. Its orbit is based on observations spanning more than a century, from 1909 February 20 to 2009 July 9.[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm)\n\n| Key fact | Detail |\n|---|---|\n| Semimajor axis | 3.11262432 AU, with perihelion distance 2.81438152 AU[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) |\n| Eccentricity | 0.09581715[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) |\n| Inclination | 19.09860936 degrees to the J2000 ecliptic, placing it among the high-inclination outer-belt objects[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) |\n| Diameter | About 94 km from the 2010 occultation solution; the DAMIT shape model gives a calibrated diameter of 102 ± 3 km[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) • [2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221) |\n| Albedo | Geometric albedo pV = 0.038 ± 0.003, a very dark surface[2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221) |\n| Rotation | Period 19.8846 hours, a slow rotator[2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221) |\n| Magnitude parameters | H = 8.94, G = 0.15[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) |\n| Family | Namesake of the compact Armenia family; classified X-complex (first-best) and T-type (second-best) in the Nesvorný 2015 catalog[3](https://poincare.matf.bg.ac.rs/~bojan.novakovic/index_e_files/high-I-families.pdf) • [4](https://academic.oup.com/mnras/article/545/3/staf2067/8339709) |\n\n## Orbit\n\nThe osculating elements computed for the 2010 March 29.899 epoch (MJD 55284.899 TDT) give a mean anomaly of 288.92409723 degrees, argument of pericenter 216.57275469 degrees, and longitude of node 145.02775630 degrees, in addition to the semimajor axis, eccentricity, and inclination listed above.[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) The solution used 820 observations with 74 rejected, drawing on astrometry from the FASTT MPC dataset via AstDys.[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) At the 2010 occultation the asteroid was 3.24200 AU from Earth.[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm)\n\n## Physical properties\n\nThe DAMIT shape model 6221, produced by Marciniak and colleagues and dated 2022-10-18, gives a diameter of 102 km with a 3 km uncertainty, a geometric albedo of 0.038 with a 0.003 uncertainty, and a convex (nonconvex flag set to no) shape solution with quality flag 3.[2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221) The spin axis is oriented at ecliptic longitude 293 degrees and latitude −23 degrees, and the rotation period is 19.8846 hours.[2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221) The model uses an Hapke (H) light-scattering description.[2](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221)\n\nArmenia is one of the slow rotators for which thermal inertia has been determined from detailed thermophysical modeling; the 2021 study notes that 780 Armenia, like [618 Elfriede](https://www.edgepedia.org/618-elfriede), has its own small, compact family, so its low thermal inertia was expected.[5](https://www.aanda.org/articles/aa/pdf/2021/10/aa40991-21.pdf)\n\n## The Armenia family\n\nA hierarchical clustering analysis of high-inclination asteroids identified a very compact family whose lowest-numbered member is (780) Armenia, one of 17 families, 21 clumps, and 4 clusters found in that region of proper-element space.[3](https://poincare.matf.bg.ac.rs/~bojan.novakovic/index_e_files/high-I-families.pdf) In the Nesvorný et al. (2015) family catalog the [Armenia family](https://www.edgepedia.org/armenia-family) appears as a compact family with a cutoff distance of 50 m/s and 40 members.[6](https://academic.oup.com/mnras/article/479/4/4815/5050391) A machine-learning study of the highly inclined outer main belt, the region between the 5J:-2A and 2J:-1A mean-motion resonances with Jupiter at sin(i) above roughly 0.3, confirmed the already known families of 31 Euphrosyne, [781 Kartvelia](https://www.edgepedia.org/781-kartvelia), 350 Ornamenta, 780 Armenia, 702 Alauda, and [704 Interamnia](https://www.edgepedia.org/704-interamnia) while extending their membership.[7](https://doi.org/10.1093/mnras/stz1795)\n\nSpectrally, the Armenia family is classified as X-complex for the first-best class and T-type for the second-best class in the NES15 taxonomy. Only two family members have Gaia DR3 spectra, and their average spectrum is noisy; the one available SDSS spectrum appears to be X-complex.[4](https://academic.oup.com/mnras/article/545/3/staf2067/8339709) Because of the low number of spectra, all of them noisy, the family was not included among the reddest families in that survey, and future near-infrared observations are expected to help link such families to meteorites.[4](https://academic.oup.com/mnras/article/545/3/staf2067/8339709)\n\n## Occultation observations\n\nA stellar occultation prediction for 2010 March 29, computed by Steve Preston using OrbFit, projected a shadow path about 99 km wide moving at 27.1266 km/s, with a 1-sigma path uncertainty of ±0.79 path widths (±3.0 seconds).[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) The asteroid's approximate diameter at that geometry was 0.040 arcseconds.[1](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm) [Occultation](https://www.edgepedia.org/occultation) observations of this kind are a direct way to measure asteroid shapes and sizes and to calibrate indirect size methods such as thermal-infrared modeling.[8](https://arxiv.org/abs/0801.2684)\n\n## References\n\n1. [RASNZ Occultation Section – Armenia Occultation Update (2010)](https://www.occultations.org.nz/planet/2010/updates/100329_780_20728_u.htm)\n2. [DAMIT – Model 6221, (780) Armenia](https://damit.cuni.cz/projects/damit/asteroid_models/view/6221)\n3. [Novaković et al., Families among high-inclination asteroids, Icarus 216 (2011)](https://poincare.matf.bg.ac.rs/~bojan.novakovic/index_e_files/high-I-families.pdf)\n4. [Searching for primitive, dark, spectrally red asteroid families in the main belt with Gaia, MNRAS 545 (2025)](https://academic.oup.com/mnras/article/545/3/staf2067/8339709)\n5. [A&A 654, A87 (2021), thermophysical modelling of slow rotators](https://www.aanda.org/articles/aa/pdf/2021/10/aa40991-21.pdf)\n6. [Quest for young asteroid families: new families, new results, MNRAS 479 (2018)](https://academic.oup.com/mnras/article/479/4/4815/5050391)\n7. [Machine-learning identification of asteroid groups, MNRAS (2019)](https://doi.org/10.1093/mnras/stz1795)\n8. [Asteroid occultations today and tomorrow: toward the GAIA era, arXiv:0801.2684](https://arxiv.org/abs/0801.2684)\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 › Asteroid families of the outer belt*\n\n*Initially written Oct 21, 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/780-armenia", "markdown_url": "https://www.edgepedia.org/780-armenia.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": "\"780 Armenia\", Edgepedia (EdgeChat), https://www.edgepedia.org/780-armenia. Edgepedia Community License 1.0.", "credit_md": "\"[780 Armenia](https://www.edgepedia.org/780-armenia)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/780-armenia](https://www.edgepedia.org/780-armenia). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"780 Armenia\", Edgepedia (EdgeChat), https://www.edgepedia.org/780-armenia. Edgepedia Community License 1.0.", "speakable": "780 Armenia, main-belt asteroid, namesake of the compact high-inclination Armenia family. Dark, ~100 km diameter, slow 19.88-hour rotation, X-complex/T-type taxonomy, semimajor axis 3.11 AU." }