# 129137 Hippolochos
**129137 Hippolochos** (provisional designation 2005 AP27) is a mid-sized Jupiter Trojan asteroid that shares Jupiter's orbit around the Sun, trapped near one of the planet's L4 or L5 Lagrange points.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) • [2](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html) Its orbit is well determined from 385 observations spanning October 2001 to June 2023, and it is not classified as a near-Earth object or as potentially hazardous.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27)
| Key fact | Detail |
|---|---|
| Classification | Jupiter Trojan (JPL orbit class TJN), not a near-Earth object and not potentially hazardous[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) • [2](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html) |
| Orbit | Semi-major axis 5.126 AU, eccentricity 0.0585, inclination 12.51 degrees[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
| Period | 4,240 days (11.61 years), with perihelion 4.83 AU and aphelion 5.43 AU[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
| Size | Estimated diameter about 8.232 km, with a brightness-based range of 6.376 to 14.257 km[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
| Brightness | Absolute magnitude 13.1[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
| Observations | 385 Minor Planet Center observations from Oct. 15, 2001 to June 28, 2023[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
| Earth safety | Orbit stays 3.83 AU from Earth's orbit at its closest point; CNEOS simulations show no close approaches[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) |
## Orbit and classification
Hippolochos belongs to the [Jupiter Trojans](https://www.edgepedia.org/jupiter-trojans), a population the [JPL Small-Body Database](https://www.edgepedia.org/jpl-small-body-database) classifies as asteroids trapped in Jupiter's L4 or L5 Lagrange points, defined by a semi-major axis between 4.6 and 5.5 AU and an eccentricity below 0.3; Hippolochos's 5.126 AU and 0.0585 fit within these bounds.[2](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html) By convention, Jupiter Trojans are named after heroes of the [Trojan War](https://www.edgepedia.org/trojan-war), which is the origin of the name Hippolochos.[3](https://universemap.net/jupiter-trojans/)
The asteroid completes one orbit every 4,240 days, or 11.61 years, moving at an average speed of 13.15 km/s. Its distance from the Sun ranges from 4.83 AU at perihelion to 5.43 AU at aphelion.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27)
## Physical characteristics
Based on its brightness and the way it reflects light, Hippolochos is estimated at roughly 8.232 km in diameter, within a probable range of 6.376 to 14.257 km, which places it among the larger asteroids of its size class. Its absolute magnitude is 13.1.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27)
## Observational record and hazard status
The orbit is determined from observations dating back to Oct. 15, 2001, with the most recent official observation on June 28, 2023; the IAU Minor Planet Center records 385 observations used in the orbit solution.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27)
Hippolochos's orbit remains 3.83 AU from [Earth's orbit](https://www.edgepedia.org/earths-orbit) at its closest point, and orbital simulations by NASA JPL's CNEOS show no close approaches to Earth, so the object 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/129137-hippolochos-2005-ap27)
## Context among Trojans
Objects with orbits similar to Hippolochos include 1867 Deiphobus (1971 EA), [2456 Palamedes](https://www.edgepedia.org/2456-palamedes) (1966 BA1), and [4068 Menestheus](https://www.edgepedia.org/4068-menestheus) (1973 SW), all named, like Hippolochos, for figures of the Trojan War.[1](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27) • [3](https://universemap.net/jupiter-trojans/) NASA's Lucy mission, launched in October 2021, is the first spacecraft sent to visit the [Trojan](https://www.edgepedia.org/trojan-celestial-body) swarms, which are thought to hold clues to how the solar system's planets formed about 4.5 billion years ago.[4](https://science.nasa.gov/solar-system/planets/jupiter/nasas-lucy-mission-a-journey-to-the-young-solar-system/)
## References
1. [Asteroid Hippolochos, Space Reference](https://www.spacereference.org/asteroid/129137-hippolochos-2005-ap27)
2. [SBDB (filter), JPL Small-Body Database API documentation](https://ssd-api.jpl.nasa.gov/doc/sbdb_filter.html)
3. [Jupiter Trojans, Universe Map](https://universemap.net/jupiter-trojans/)
4. [NASA's Lucy Mission: A Journey to the Young Solar System, NASA Science](https://science.nasa.gov/solar-system/planets/jupiter/nasas-lucy-mission-a-journey-to-the-young-solar-system/)
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*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Jupiter Trojans and other dynamical groups › Trojan-camp Jupiter Trojans*
*Initially written Oct 20, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license