NASA SBDB Data · Astrophyzix Scientific Close‑Approach & Orbital Report
Asteroid 2021 KN2 — Elite‑Tier NEO Close‑Approach & Orbital Profile · JPL SBDB Solution JPL 3
✅ Data aligned with: JPL SBDB, CNEOS CAD, NASA Horizons - Last verified against JPL SBDB: 31 May 2026 13:42 UTC
Key Takeaways of Asteroid 2021 KN2
- NASA JPL Solution: Solution JPL 3 · Epoch 2461000.5 (2025‑Nov‑21.0 TDB) · SPK‑ID 54149826 · Producer: Otto Matic
- Orbit class: Apollo NEO — a = 1.4064 au, e = 0.3718, i = 3.77°, orbital period 609.23 days (1.67 years).
- Earth MOID: 0.001331 au (~199,000 km), placing the nominal orbit well inside the Earth–Moon system, but with no impact solutions in current JPL or CNEOS catalogues.
- Size estimate: Absolute magnitude H = 28.63 → approximate diameter ~5–12 m (albedo‑dependent), firmly in the small NEO regime.
- Rotation: Extremely fast rotation period of 0.021007 h (~75.6 seconds), based on LCDB data, suggesting a cohesive or monolithic body rather than a loose rubble pile.
- Orbit quality: Condition code 6, based on 65 observations over a 1‑day data arc (2021‑05‑30 to 2021‑05‑31), with a normalised RMS of 0.23451 — a short‑arc, moderately uncertain orbit.
- Recent close approach: On 2021‑05‑31, 2021 KN2 passed Earth at a nominal distance of 0.00097 au (~145,000 km) and the Moon at 0.00306 au, a close but non‑impacting flyby.
- Risk context: Not a Potentially Hazardous Asteroid — too small (H > 22) and no impact geometry in current solutions.
- Ignore clickbait and sensational claims about “mystery asteroids nearly hitting Earth” — the official data show 2021 KN2 as a small, well‑tracked, non‑hazardous NEO.
Scientific Consensus Snapshot of 2021 KN2
| Parameter | Status |
|---|---|
| Orbit class | Apollo NEO (a > 1 au, q < 1.017 au — Earth‑crossing) |
| Epoch | 2461000.5 TDB (2025‑Nov‑21.0) — heliocentric IAU76/J2000 ecliptic |
| Semi‑major axis (a) | 1.4064396667 au |
| Eccentricity (e) | 0.3717549887 |
| Perihelion distance (q) | 0.8835887043 au |
| Aphelion distance (Q) | 1.9292906290 au |
| Inclination (i) | 3.76531182° |
| Earth MOID | 0.001331 au (~199,000 km) |
| Jupiter MOID | 3.32842 au |
| Tisserand parameter (TJ) | 4.663 |
| Absolute magnitude (H) | 28.63 (very small object) |
| Rotation period | 0.021007 h (~75.6 s) — LCDB (Rev. 2023‑October) |
| Condition code | 6 (short‑arc, moderate uncertainty) |
| Observations / data arc | 65 observations over 1 day (2021‑05‑30 → 2021‑05‑31) |
| Hazard level | Non‑hazardous size; no impact geometry in current solutions |
2021 KN2 Close‑Approach Overview
| Date/Time (TDB) | Body | Nominal distance (au) | Min–Max distance (au) | Vrel (km/s) |
|---|---|---|---|---|
| 2021‑05‑31 02:14 ± < 00:01 | Earth | 0.00097 | 0.00097 – 0.00097 | 9.82 |
| 2021‑05‑31 00:04 ± < 00:01 | Moon | 0.00306 | 0.00306 – 0.00306 | 8.79 |
| 2016‑10‑12 09:23 ± 13:24 | Earth | 0.15221 | 0.14332 – 0.16115 | 13.81 |
| 2008‑05‑11 01:25 ± 1:02:41 | Earth | 0.29014 | 0.26877 – 0.31151 | 18.00 |
| 2003‑09‑01 11:20 ± 8:08:23 | Earth | 0.12131 | 0.10856 – 0.13426 | 7.38 |
| 2003‑05‑05 18:45 ± 7:03:04 | Earth | 0.40515 | 0.38255 – 0.42776 | 4.30 |
| 2015‑06‑02 20:10 ± 5:40 | Mars | 0.02237 | 0.01664 – 0.02979 | 6.11 |
| 1990‑12‑26 01:17 ± 4:04:06 | Mars | 0.08696 | 0.06153 – 0.11289 | 5.21 |
| 2026‑Jun‑03 06:52 ± 1:04:45 | Earth | (distance in SBDB CAD; non‑impacting) | — | — |
1. Asteroid 2021 KN2
Asteroid 2021 KN2 Orbital Geometry
| Parameter | Value |
|---|---|
| Orbit class | Apollo (APO) — Earth‑crossing NEO |
| Epoch | 2461000.5 TDB (2025‑Nov‑21.0) |
| Semi‑major axis (a) | 1.4064396667 au |
| Eccentricity (e) | 0.3717549887 |
| Perihelion distance (q) | 0.8835887043 au |
| Aphelion distance (Q) | 1.9292906290 au |
| Inclination (i) | 3.76531182° |
| Longitude of node (Ω) | 70.33462147° |
| Argument of perihelion (ω) | 237.38184830° |
| Mean anomaly (M) | 218.87371464° |
| Mean motion (n) | 0.5909114619 deg/day |
| Time of perihelion (tp) | 2461239.3281400 TDB (2026‑Jul‑17.828) |
| Orbital period | 609.2283 days (1.6680 years) |
| Earth MOID | 0.001331 au (~199,000 km) |
| Jupiter MOID | 3.32842 au |
| Tisserand parameter (TJ) | 4.663 |
Physical Characteristics of NEO 2021 KN2
| Parameter | Value |
|---|---|
| Absolute magnitude (H) | 28.63 |
| Estimated diameter | ~5–12 m (assuming albedo 0.25–0.05) |
| Rotation period | 0.021007 h (~75.6 s) — LCDB (Rev. 2023‑October) |
| Spectral type | Unknown (no published taxonomy) |
| PHA classification | No — H > 22 (below PHA size threshold) |
| Condition code | 6 (short‑arc, moderate uncertainty) |
Upcoming Close Approach — 3 June 2026
| Parameter | Value |
|---|---|
| Approach date (TDB) | 2026‑06‑03 06:52 ± 1 day 04:45 |
| Body | Earth |
| Nominal distance | Listed in SBDB CAD (non‑impacting) |
| Minimum–maximum distance | Within safe, non‑intersecting bounds |
| Relative velocity | Not yet fully constrained (short‑arc object) |
| Orbit solution | JPL 3 (65 observations, 1‑day arc) |
Interpretation of the 2026 Close Approach
The 3 June 2026 encounter is the first post‑discovery Earth approach for 2021 KN2 since its extremely close 2021 flyby (0.00097 au). Unlike that event, the 2026 passage occurs at a much larger and fully safe distance, with no overlap between the uncertainty region and any Earth‑impact corridor.
Because 2021 KN2 was observed for only one day in 2021, its orbit retains a moderate uncertainty (condition code 6). The 2026 apparition is therefore scientifically important: it will allow new astrometric measurements that will extend the data arc from 1 day to 5 years, dramatically improving the orbit solution and reducing the condition code.
The 2026 approach is safe, non‑hazardous, and scientifically valuable. It provides an opportunity for orbit refinement, rotational‑state confirmation, and follow‑up photometry of this extremely fast‑spinning (~75.6 s) small Apollo NEO.
Astrophyzix Digital Observatory Interpretation and FAQ
1. How close did 2021 KN2 really come to Earth?
On 2021‑05‑31, 2021 KN2 passed Earth at a nominal distance of 0.00097 au, which is roughly 145,000 km — closer than the Moon’s average distance (~384,000 km), but still well outside Earth’s atmosphere. This is very close astronomically, but dynamically it remained a clean miss with no impact corridor.
2. What does the very small Earth MOID mean?
The Earth MOID of 0.001331 au (~199,000 km) means that the orbits of Earth and 2021 KN2 come very close in space. MOID is a geometric measure; it does not guarantee that both bodies are at that point at the same time. Current JPL solutions show no impact trajectories despite the low MOID.
3. Why is the rotation period important?
With a rotation period of just 0.021007 h (~75.6 seconds), 2021 KN2 is an extreme fast rotator. Such rapid spin rates are typically only possible for small, cohesive bodies; larger rubble‑pile asteroids would disrupt at these speeds. This makes 2021 KN2 an interesting target for studies of small‑body strength and internal structure.
4. Is 2021 KN2 a Potentially Hazardous Asteroid?
No. By definition, Potentially Hazardous Asteroids (PHAs) must be both large enough (H ≤ 22, roughly ≥ 140 m) and have a sufficiently small MOID. 2021 KN2 has H = 28.63, implying a diameter of only a few to ~10 metres. It is far below the PHA size threshold and is not listed as a PHA by any agency.
5. What happens next for 2021 KN2?
Future apparitions will allow additional astrometry to extend the data arc beyond the current 1‑day span. As more observations are added, the condition code (currently 6) will decrease, and the orbit will become more precisely defined. Astrophyzix will track new JPL solutions and update the orbital profile if any close‑approach geometry changes in a scientifically meaningful way.
Track live: Astrophyzix Live Orbital Viewer
Risk Assessment
No impact threat.
- Current JPL SBDB and CNEOS solutions show no impact trajectories for 2021 KN2.
- The 2021 Earth–Moon flyby was a close but clean miss, and future approaches remain non‑impacting in all published solutions.
Not a PHA.
- With H = 28.63, 2021 KN2 is far below the size threshold for Potentially Hazardous Asteroids.
- It is not classified as a PHA and does not appear on PHA lists.
Short‑arc uncertainty.
- The condition code of 6 reflects a 1‑day observation arc.
- This is normal for small NEOs discovered and tracked over short intervals and does not imply a hidden impact risk.
Energy regime.
- At an estimated ~5–12 m diameter, 2021 KN2 lies below the Chelyabinsk energy regime and far below the Tunguska scale.
- Even in a hypothetical impact scenario, it would be a local‑scale airburst at most, not a regional hazard.
Operational context.
- The close 2021 flyby and low MOID are of scientific and monitoring interest, but they do not threaten satellites or infrastructure.
- Orbital geometry and altitude differ significantly from operational satellite orbits.
Astrophyzix Digital Observatory Scientific Summary
Asteroid 2021 KN2 is a small, fast‑rotating Apollo‑class Near‑Earth Object with a moderately eccentric (e ≈ 0.37), low‑inclination (i ≈ 3.8°) orbit and a semi‑major axis of a ≈ 1.41 au. Its orbit crosses Earth’s orbital distance near perihelion and extends to Q ≈ 1.93 au, with an orbital period of ~1.67 years and a Tisserand parameter TJ = 4.663, consistent with a typical asteroidal NEO.
The Earth MOID of 0.001331 au (~199,000 km) and the 2021‑05‑31 Earth flyby at 0.00097 au (~145,000 km) make 2021 KN2 geometrically noteworthy, placing its trajectory well inside the Earth–Moon system at closest approach. However, current JPL SBDB and CNEOS solutions show no impact solutions, and all listed encounters are non‑impacting.
With an absolute magnitude of H = 28.63, 2021 KN2 is a very small NEO, likely only a few to ~10 metres in diameter. Its physical scale places it far below the threshold for Potentially Hazardous Asteroids and well below the Chelyabinsk energy regime. The extremely short rotation period of ~75.6 seconds makes it an interesting case study in small‑body cohesion and internal strength.
The current orbit solution — condition code 6, 65 observations, 1‑day data arc, normalised RMS 0.23451 — represents a short‑arc, moderately uncertain orbit. This is typical for small NEOs discovered near close approach and is expected to improve as additional astrometry is acquired in future apparitions.
From a planetary‑defence standpoint, 2021 KN2 is safe, non‑hazardous, and scientifically routine in current solutions. Its primary 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 — 2021 KN2
- CNEOS Close‑Approach Tables
- NASA Scout Impact Monitoring
- NASA Horizons Ephemeris System