{ "id": "epdhx2q1tt", "slug": "12658-peiraios", "title": "12658 Peiraios", "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.greek-camp-jupiter-trojans", "label": "Greek-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans" }, { "id": "places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans.heroes-of-the-odyssean-circle", "label": "Heroes of the Odyssean circle", "api_url": "https://www.edgepedia.org/api/v1/topics/places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans.heroes-of-the-odyssean-circle" } ], "geo": [ { "id": "geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans", "label": "Non-geographic · Not dated: Greek-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-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.greek-camp-jupiter-trojans", "label": "Greek-camp Jupiter Trojans", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.nodate.places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans" } ] } ], "excerpt": "12658 Peiraios (provisional designation 1973 SL) is a Jupiter Trojan asteroid at Jupiter's leading L4 Lagrange point, about 26 km in diameter, discovered in 1973 at Palomar Observatory.", "snippet": "12658 Peiraios (provisional designation 1973 SL) is a Jupiter Trojan asteroid at Jupiter's leading L4 Lagrange point, about 26 km in diameter, discovered in 1973 at Palomar Observatory.", "node": "places.extraterrestrial.small-bodies.asteroids-trojans-and-outer-groups.greek-camp-jupiter-trojans.heroes-of-the-odyssean-circle", "markdown": "# 12658 Peiraios\n\n**12658 Peiraios** (provisional designation **1973 SL**) is a Jupiter Trojan asteroid, one of the bodies trapped near Jupiter's leading L4 Lagrange point (orbital position where gravitational forces balance, allowing trapped bodies), about 26 km in diameter.\n|---|---|\n| Designation | Minor planet 12658, provisional designation 1973 SL, named Peiraios[6](https://asteroidname.com/asteroid/peiraios) |\n| Discovery | 19 September 1973, Palomar Observatory, by C. J. van Houten, I. van Houten-Groeneveld, and T. Gehrels (Palomar-Leiden Survey)[6](https://asteroidname.com/asteroid/peiraios) |\n| Dynamical class | Jupiter Trojan, L4 camp; JPL defines the class as asteroids trapped in Jupiter's L4/L5 Lagrange points with 4.6 au < a < 5.5 au and e < 0.3[1](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html) • [2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) |\n| Orbit | Semimajor axis about 5.168 au, eccentricity about 0.057, inclination about 1.78 degrees[3](https://iaaras.ru/html/emp2020/emp_2020/elm_2020/20_012001.pdf) |\n| Size | Estimated diameter about 26 km[6](https://asteroidname.com/asteroid/peiraios) |\n| Rotation | Period 8.151 ± 0.003 hours, lightcurve amplitude 0.562 ± 0.033 magnitudes[4](https://real.mtak.hu/156658/1/2102.09447.pdf) |\n| Photometry | Absolute magnitude H = 11.2; ATLAS c−o color −0.130 ± 0.091 mag; phase parameter G = 0.454 ± 0.166[2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) |\n\n## Discovery\n\nThe body received the provisional designation 1973 SL and, after its orbit was secured, the permanent number 12658 and the name Peiraios.[6](https://asteroidname.com/asteroid/peiraios)\n\n## Orbit and dynamical class\n\nPeiraios belongs to the L4 camp of [Jupiter Trojans](https://www.edgepedia.org/jupiter-trojans), the swarm of asteroids that librates around Jupiter's leading [Lagrange point](https://www.edgepedia.org/lagrange-point), 60 degrees ahead of the planet in its orbit.[2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) In JPL's Small-Body Database classification scheme, a Jupiter Trojan (code TJN) is an asteroid trapped in Jupiter's L4 or L5 Lagrange points, defined by a semimajor axis between 4.6 and 5.5 au and an eccentricity below 0.3.[1](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html) Peiraios fits this class comfortably: its osculating semimajor axis is about 5.168 au, with an eccentricity of about 0.057 and an inclination of about 1.78 degrees to the ecliptic.[3](https://iaaras.ru/html/emp2020/emp_2020/elm_2020/20_012001.pdf) Its low inclination places it near the core of the Trojan swarm, where number densities are highest.\n\n## Physical properties\n\n**Size and brightness.** The ATLAS survey photometry yields an absolute magnitude H of 11.2, meaning the brightness the body would have at 1 au from both the Sun and the observer at zero phase angle.[2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) For a body of this size and magnitude, the implied surface is dark, consistent with the Trojan population as a whole: thermal measurements of the largest, well-measured Trojans give a mean V-band albedo of only about 5 to 7 percent, values similar to dark cometary nuclei.[5](https://link.springer.com/article/10.1007/s11214-024-01060-7)\n\n**Rotation and shape.** A photometric campaign reported by Kalup and colleagues in 2021 determined a rotation period of 8.151 ± 0.003 hours with a lightcurve amplitude of 0.562 ± 0.033 magnitudes.[4](https://real.mtak.hu/156658/1/2102.09447.pdf) An amplitude of this size indicates a noticeably elongated body, since the brightness range over one rotation mainly reflects the changing projected area of an irregular shape.\n\n**Color.** From ATLAS cyan and orange filter observations, Peiraios has a c−o color of −0.130 ± 0.091 magnitudes and a fitted phase-curve parameter G of 0.454 ± 0.166.[2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) The c−o color is one of the diagnostics used to separate asteroid taxonomic types from the two-filter ATLAS photometry.\n\n## Context among the Trojans\n\nJupiter's Trojan swarms contain nearly 8,000 known co-orbital asteroids, with the L4 cloud holding roughly 1.8 times as many cataloged objects as L5 as of early 2020.[2](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data) Peiraios is one of the many L4 members in the 20 to 30 km size range. Like most Trojans, it was long known only from sparse survey photometry; dedicated time-series campaigns such as the one that fixed its 8.15-hour rotation period are what allow individual objects in this population to be characterized.[4](https://real.mtak.hu/156658/1/2102.09447.pdf)\n\n## References\n\n1. [SBDB Filter Parameters, JPL Solar System Dynamics](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html)\n2. [A. McNeill et al. (2021). Comparison of the Physical Properties of the L4 and L5 Trojan Asteroids from ATLAS Data. The Planetary Science Journal 2:6](https://www.researchgate.net/publication/348699143_Comparison_of_the_Physical_Properties_of_the_L4_and_L5_Trojan_Asteroids_from_ATLAS_Data)\n3. [Ephemerides of minor planets 2020, Table of elements, Institute of Applied Astronomy RAS](https://iaaras.ru/html/emp2020/emp_2020/elm_2020/20_012001.pdf)\n4. [Kalup et al. (2021). Rotation periods and amplitudes of Jupiter Trojans, arXiv:2102.09447](https://real.mtak.hu/156658/1/2102.09447.pdf)\n5. [Surface Compositions of Trojan Asteroids, Space Science Reviews (2024)](https://link.springer.com/article/10.1007/s11214-024-01060-7)\n6. [(12658) Peiraios – asteroid discovered 1973 | AsteroidName](https://asteroidname.com/asteroid/peiraios)\n\n---\n*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Jupiter Trojans and other dynamical groups › Greek-camp Jupiter Trojans › Heroes of the Odyssean circle*\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/12658-peiraios", "markdown_url": "https://www.edgepedia.org/12658-peiraios.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": "\"12658 Peiraios\", Edgepedia (EdgeChat), https://www.edgepedia.org/12658-peiraios. Edgepedia Community License 1.0.", "credit_md": "\"[12658 Peiraios](https://www.edgepedia.org/12658-peiraios)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/12658-peiraios](https://www.edgepedia.org/12658-peiraios). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"12658 Peiraios\", Edgepedia (EdgeChat), https://www.edgepedia.org/12658-peiraios. Edgepedia Community License 1.0.", "speakable": "12658 Peiraios is a Jupiter Trojan asteroid at Jupiter's leading L4 Lagrange point, about 26 km in diameter, discovered in 1973 at Palomar Observatory." }