Astrophyzix Near-Earth Object (NEO) Close Approach Report: 363599 (2004 FG11) Official Data, Real Time Reporting
Written by: Astrophyzix Digital Observatory
Image Credit: NASA JPL SBDB
2026 Relevance: Illustrates orbital geometry and Earth-approach context for monitored near-Earth objects during the 2026 observation window.
Introduction
Asteroid 363599 (2004 FG11) is a well-studied Apollo-class near-Earth object (NEO) and is formally classified as a Potentially Hazardous Asteroid (PHA). This classification arises from its size and orbital proximity to Earth, specifically its Minimum Orbit Intersection Distance (MOID). The object has been extensively observed since its discovery in 2004, resulting in a highly refined orbital solution with exceptionally low uncertainty.
Notably, (2004 FG11) is a binary system with a confirmed satellite, making it scientifically significant for studies of asteroid mass, density, and internal structure. Its repeated close approaches to Earth make it a key object in long-term planetary defence monitoring.
Key Takeaways
- Binary Apollo-class NEO and Potentially Hazardous Asteroid (PHA).
- Highly reliable orbit (condition code 0) based on 22+ years of observations.
- Estimated diameter: ~152 meters with relatively high albedo (0.306).
- Rotation period: ~7.02 hours.
- Earth MOID: 0.0203 AU (~3.04 million km).
- Regular Earth close approaches approximately every 2 years.
- Next significant Earth approach: 2026-Apr-11 at 0.05652 AU (~8.46 million km).
- No impact risk identified in current orbital solutions.
Scientific Consensus Snapshot
The orbital solution for (2004 FG11) is based on 507 optical observations and radar astrometry spanning over 22 years. The inclusion of radar delay and Doppler measurements significantly enhances orbital precision, resulting in a condition code of 0. This allows for highly accurate forward propagation of the orbit and reliable close-approach predictions.
Orbital Profile
- Orbit Type: Apollo-class (Earth-crossing)
- Semi-major axis (a): 1.586 AU
- Eccentricity (e): 0.724
- Inclination (i): 3.13°
- Perihelion (q): 0.438 AU
- Aphelion (Q): 2.735 AU
- Orbital Period: ~730 days (~2.00 years)
- Earth MOID: 0.0203 AU (~3.04 million km)
- Tisserand Parameter (Jupiter): 4.041
Physical & Structural Characteristics
- Absolute Magnitude (H): 21.05
- Estimated Diameter: 0.152 km (152 meters)
- Geometric Albedo: 0.306 (relatively reflective surface)
- Rotation Period: 7.021 hours
- Binary System: Confirmed secondary satellite (discovered 2012)
The presence of a satellite suggests a rubble-pile or gravitational aggregate structure, which has implications for impact modelling and potential deflection strategies. Binary systems provide rare opportunities for direct mass estimation through orbital dynamics of the secondary body.
Close Approach Analysis
| Date (TDB) | Distance (AU) | Distance (LD) | Velocity (km/s) |
|---|---|---|---|
| 2020-Apr-11 | 0.04920 | ~19.1 LD | 24.49 |
| 2022-Apr-12 | 0.04942 | ~19.2 LD | 24.50 |
| 2024-Apr-11 | 0.05210 | ~20.3 LD | 24.74 |
| 2026-Apr-11 | 0.05652 | ~22.0 LD | 25.07 |
| 2028-Apr-10 | 0.06393 | ~24.9 LD | 25.41 |
2026 Close Approach Context
The April 11, 2026 close approach occurs at a distance of 0.05652 AU (~8.46 million km), equivalent to approximately 22 lunar distances. While this qualifies as a relatively close astronomical pass, it remains well outside any risk threshold. The encounter velocity of ~25.07 km/s is typical for Apollo-class objects intersecting Earth's orbital region.
The regular ~2-year encounter cadence reflects the asteroid’s orbital resonance relative to Earth, although no dangerous resonant return trajectories are identified in current models.
Dynamical Behaviour & Evolution
The orbit of (2004 FG11) is moderately eccentric, bringing it from inside the orbit of Venus out toward the inner main asteroid belt. Its low inclination means frequent crossings of the ecliptic plane, increasing the likelihood of repeated planetary encounters over long timescales.
The inclusion of a measured non-gravitational acceleration term (A2) suggests minor orbital drift effects, potentially related to the Yarkovsky effect. This is particularly relevant for long-term trajectory prediction and impact probability assessment over centuries.
Risk Assessment
Although classified as a Potentially Hazardous Asteroid, (2004 FG11) does not pose any known impact threat based on current orbital solutions:
- Highly constrained orbit (condition code 0).
- All known close approaches remain well outside impact thresholds.
- Long observational arc enables accurate long-term trajectory modelling.
- Binary nature does not increase impact probability but is relevant for mitigation planning.
- ARI score at time of publication: 47/100 (safe) *
Conclusion
Asteroid 363599 (2004 FG11) is a scientifically significant and well-characterised near-Earth object. Its binary nature, stable observational history, and predictable orbital behaviour make it an important target for ongoing planetary defence monitoring and research.
The April 2026 close approach will occur at a safe distance with no impact risk. Continued tracking ensures that any long-term orbital evolution—particularly due to non-gravitational forces—remains fully accounted for in future risk assessments.