NASA CAD Data · Astrophyzix Scientific Close-Approach & Orbital Report
Top-down schematic. Orbit size and shape are drawn from the published elements (a, e, q, Q); the orientation of the orbit and the marked encounter point are approximate.
Key Takeaways of Asteroid 2026 SY2
- Close approach: 21 Sep 2026 at 11:25 TDB (timing uncertainty under 1 minute), confirmed in the JPL CAD record. The miss distance was 2.433 LD (≈ 935,356 km, 0.00625 au).
- Speed: 25.14 km/s relative to Earth (≈ 90,500 km/h); v∞ 25.13 km/s.
- Orbit class: Apollo NEO — a = 2.24 au, e = 0.795, i = 3.16°, orbital period ≈ 1,220 days (3.34 years).
- Earth MOID: 0.0062 au (≈ 0.93 million km). The approach distance matches the MOID to within rounding, so 2026 SY2 passed almost as close to Earth's orbit as its geometry allows.
- Size estimate: absolute magnitude H = 27.457, giving a diameter of about 11.5 m (range 8.6–19.2 m, albedo-dependent). The size is H-derived, not measured.
- Orbit quality: the solution rests on a 1-day data arc with 35 observations, so the orbital elements are provisional.
- Risk context: not a Potentially Hazardous Asteroid (H is far above 22), not on the Sentry watchlist, and no Scout entry.
- Keep it in proportion: flybys of small asteroids inside a few lunar distances are routine and are exactly what modern surveys are built to find. This one was tracked, confirmed and non-hazardous.
Approach Scale
Scientific Consensus Snapshot of 2026 SY2
| Parameter | Status |
|---|---|
| Orbit class | Apollo NEO (a > 1 au, q < 1.017 au — Earth-crossing) |
| Semi-major axis (a) | 2.24 au |
| Eccentricity (e) | 0.795 |
| Perihelion distance (q) | 0.459 au |
| Aphelion distance (Q) | 4.01 au |
| Inclination (i) | 3.16° |
| Orbital period | ≈ 1,220 days (3.34 years) |
| Earth MOID | 0.0062 au (≈ 0.93 million km) |
| Tisserand parameter (TJ) | ≈ 3.12 † — consistent with an asteroidal orbit |
| Absolute magnitude (H) | 27.457 (very small object) |
| Estimated diameter | ≈ 11.5 m (8.6–19.2 m), H-derived |
| Observations / data arc | 35 observations over 1 day |
| Sentry / Scout | Not on Sentry watchlist · no Scout entry |
| Hazard level | Non-hazardous size; not PHA-class |
† Derived by Astrophyzix from a, e and i. All other values are taken from the JPL CAD record and observatory sync.
2026 SY2 Close-Approach Overview
| Date/Time (TDB) | Body | Nominal distance | Min–Max distance (au) | Vrel (km/s) |
|---|---|---|---|---|
| 2026-09-21 11:25 ± < 00:01 | Earth | 0.00625 au 2.433 LD | 0.00620 – 0.00630 | 25.14 |
Same-day company
Two other objects made close passes earlier the same day (monitoring window 21–22 Sep 2026):
| Object | Date/Time (TDB) | Miss distance | Velocity | ARI |
|---|---|---|---|---|
| 2026 SN2 | 2026-09-21 01:02 | 2.466 LD | 13.52 km/s | 40 |
| 2026 SY | 2026-09-21 00:34 | 5.544 LD | 9.80 km/s | — |
1. Asteroid 2026 SY2
Small Apollo NEO on a highly elongated orbit, with a lunar-distance flyby on 21 September 2026 and a very low Earth MOID — dynamically interesting, but non-hazardous in current solutions.
Asteroid 2026 SY2 Orbital Geometry
| Parameter | Value |
|---|---|
| Orbit class | Apollo (APO) — Earth-crossing NEO |
| Semi-major axis (a) | 2.24 au |
| Eccentricity (e) | 0.795 |
| Perihelion distance (q) | 0.459 au |
| Aphelion distance (Q) | 4.01 au |
| Inclination (i) | 3.16° |
| Mean motion (n) | ≈ 0.295 deg/day † |
| Orbital period | ≈ 1,220 days (3.34 years) |
| Earth MOID | 0.0062 au (≈ 0.93 million km) |
| Data arc | 1 day |
| Observations used | 35 |
Physical Characteristics of NEO 2026 SY2
| Parameter | Value |
|---|---|
| Absolute magnitude (H) | 27.457 |
| Estimated diameter | ≈ 8.6–19.2 m (nominal 11.5 m, assuming albedo 0.25–0.05) |
| Size source | H-derived (no radar or thermal measurement) |
| Rotation period | Not published |
| Spectral type | Unknown (no published taxonomy) |
| PHA classification | No — H > 22 (below PHA size threshold) |
2026 SY2 is a small Apollo NEO whose orbit swings from between Mercury's and Venus's distances from the Sun out beyond the main asteroid belt, toward Jupiter's orbit. Its orbit passes only 0.0062 au from Earth's at the closest point, and on 21 September 2026 the asteroid passed Earth at almost exactly that distance — about 2.4 times the Moon's. At a diameter of roughly a dozen metres it is far below the size threshold for Potentially Hazardous Asteroids and is considered routine by planetary-defence standards.
Interpretation of the 2026 Close Approach
The designation places the discovery in the second half of September 2026, which fits a 1-day observation arc. With so little astrometry, the orbit carries real uncertainty in its long-term elements, even though the CAD solution pins down this particular passage to well under a minute.
Because the arc is short, the past and future encounter geometry of 2026 SY2 cannot yet be predicted reliably. Follow-up observations over the coming days and weeks will lengthen the arc, tighten the elements and allow the object's future close approaches to be screened properly.
Astrophyzix Assessment:
The 21 September 2026 approach was safe, non-hazardous and scientifically useful. It adds a well-timed data point on how the small-NEO population is sampled by current surveys, and the object is a candidate for follow-up astrometry to refine its orbit.
Astrophyzix Risk Index (ARI)
43 / 100 for 2026 SY2 (ARI 40 for 2026 SN2 on the same day).
ARI is an Astrophyzix composite index used to rank close approaches at a glance. It is not an official NASA, ESA or IAU hazard rating; the authoritative impact-risk sources are Sentry and Scout.
Astrophyzix Digital Observatory Interpretation and FAQ
1. How close did 2026 SY2 really come to Earth?
On 2026-09-21 the asteroid passed at a nominal distance of 0.00625 au, about 935,000 km or 2.43 lunar distances. That is roughly 147 Earth radii and more than 20 times the distance of geostationary satellites — close in astronomical terms, but far outside any atmospheric or orbital-infrastructure concern.
2. What does the very small Earth MOID mean?
The Earth MOID of 0.0062 au means that the orbits of Earth and 2026 SY2 come within about 0.93 million km of each other at their nearest points. MOID is a geometric measure; it does not mean both bodies are at that spot at the same time. On 21 September the timing happened to bring them there together.
3. Why does the 1-day data arc matter?
Orbit accuracy depends on how long an object has been observed. A 1-day arc with 35 observations is enough to compute the current passage well, but not to predict encounters years ahead. This is normal for small NEOs found close to Earth and does not imply a hidden impact risk.
4. Is 2026 SY2 a Potentially Hazardous Asteroid?
No. A PHA must have an absolute magnitude H ≤ 22 (roughly 140 m or larger) and an Earth MOID of 0.05 au or less. 2026 SY2 meets the MOID condition, but with H = 27.457 it is only about a dozen metres across and is far below the size threshold.
5. What happens next for 2026 SY2?
Follow-up astrometry from professional and amateur observers will lengthen the data arc. Faint, fast-receding objects like this one are often lost to observation within days, so the orbit may remain modestly constrained. Astrophyzix will update this profile if the JPL solution changes in a meaningful way.
Track live: Astrophyzix Live Orbital Viewer
Risk Assessment
No impact threat.
- 2026 SY2 is not on the Sentry watchlist and has no Scout entry at the time of the observatory sync.
- The 21 September 2026 flyby was a clean miss at 2.433 LD.
Not a PHA.
- With H = 27.457, 2026 SY2 is far below the size threshold for Potentially Hazardous Asteroids.
- The Astrophyzix classifier records it as below the PHA-class threshold (derived).
Short-arc uncertainty.
- The 1-day observation arc and 35 observations make the orbital elements provisional.
- This is typical for small NEOs discovered close to Earth and does not imply a hidden impact risk.
Energy regime.
- At an estimated ~11 m diameter, 2026 SY2 is smaller than the 2013 Chelyabinsk impactor (roughly 18–20 m) and far below the Tunguska scale.
- Objects of this size enter Earth's atmosphere about once a decade on average, and would end as a local-scale airburst at most, not a regional hazard.
Operational context.
- The flyby passed far beyond geostationary distance and poses no threat to satellites or infrastructure.
Astrophyzix Digital Observatory Scientific Summary
Asteroid 2026 SY2 is a small Apollo-class Near-Earth Object on a highly eccentric (e ≈ 0.80), low-inclination (i ≈ 3.2°) orbit with a semi-major axis of a ≈ 2.24 au. Its orbit ranges from q ≈ 0.46 au to Q ≈ 4.01 au, with a period of about 3.3 years and a Tisserand parameter near 3.1, consistent with a typical asteroidal NEO.
On 21 September 2026 it passed Earth at 0.00625 au (≈ 935,000 km, 2.43 LD) at 25.14 km/s, essentially at the Earth MOID of 0.0062 au. It is not on the Sentry watchlist and has no Scout entry.
With an absolute magnitude of H = 27.457, it is a very small NEO, likely around 9–19 m across, with a nominal size near 11.5 m. Its physical scale places it far below the threshold for Potentially Hazardous Asteroids and below the Chelyabinsk energy regime.
The current orbit rests on 35 observations over a 1-day arc, so the elements are provisional and will improve as additional astrometry is obtained. From a planetary-defence standpoint, 2026 SY2 is safe, non-hazardous and scientifically routine. Its main value lies in orbit refinement, survey-performance benchmarking and public education about how close-approach geometry and MOID are interpreted in modern NEO monitoring.
Sources
- NASA/JPL Small-Body Database — 2026 SY2
- CNEOS Close-Approach Tables (JPL CAD)
- CNEOS Sentry Impact Monitoring
- NASA Scout Impact Monitoring
- NASA Horizons Ephemeris System
