NASA Scout / NEOCP Data · Astrophyzix Preliminary Object Alert
Key Takeaways of SWAN26Q
- Status: SWAN26Q is an unconfirmed Near-Earth Object Confirmation Page (NEOCP) candidate, triaged by NASA's Scout system rather than carrying a confirmed JPL orbit. It has not yet been evaluated by Sentry.
- Most recent data point: last Scout run 2026-09-16 18:24 UTC, based on 9 observations spanning a 743-day arc — sparse but long-baseline tracking.
- Current geometry: nominal distance 15.567 LD (≈ 5,983,915 km, 0.04 au) at 56.70 km/s — both figures come from a short, unevenly sampled arc and should be read as preliminary.
- Size estimate: H = 11.7 gives a diameter of roughly 12–27 km (nominal ≈ 16 km, albedo-dependent) — far larger than the small metre-scale NEOs in Astrophyzix's usual daily reports.
- PHA classification: Scout's automated scoring flags it PHA-class (phaScore 100), driven by its size and a modeled MOID of 0.04 au. This is a preliminary triage flag, not a Sentry-confirmed hazard designation.
- Unusual orbit: sampled orbits show an eccentricity of 0.997–1.000 (essentially parabolic) and an inclination near 109° (retrograde). That combination — plus a name prefix historically associated with SOHO/SWAN comet discoveries — is far more typical of a long-period or first-time-inbound comet than a rocky asteroid.
- No impact signal: of 300 Monte Carlo orbits sampled from the current fit, 0.0% show an Earth-impact flag. This is reassuring but is explicitly not a formal impact probability, and will keep being refined as more astrometry arrives.
- Why the data is thin: at a solar elongation of only 14°, SWAN26Q currently sits deep in the Sun's glare — a difficult, often impossible, position to observe from the ground, which explains the sparse observation count and the 11-day-old last Scout run.
Sampled Orbit Cloud
Because the observation arc is short, Scout does not report one fixed orbit — it fits many plausible orbits (here, 300 samples) consistent with the 9 observations and shows the spread. The two parameters that vary meaningfully are inclination and eccentricity:
The tight inclination cluster (all samples within 0.03° of each other) shows this dimension is already well pinned down. Eccentricity is less certain, but every sample sits at or just below the parabolic boundary (e = 1) — the orbit is essentially unbound or only very marginally bound to the Sun. No semi-major axis, perihelion or orbital period is quoted here because at e ≈ 1 those quantities are undefined or extremely sensitive to small changes in the fit; a standard Apollo/Aten/Amor classification does not apply to an orbit this eccentric.
300 sampled orbits fit to the current observation arc. 0.0% of samples are flagged as potential Earth impactors (impFlag) — expected to fall toward, and stay at, zero as more observations arrive. This is Scout's internal screening metric, not a calculated impact probability.
Approach Scale
Note the scale change from Astrophyzix's usual close-approach reports (typically 0–2 LD): SWAN26Q's current nominal distance is much farther out, more than seven times the Moon's distance.
Scientific Consensus Snapshot of SWAN26Q
| Parameter | Status |
|---|---|
| Source / confirmation | Scout (NEOCP) — unconfirmed, not yet in JPL SBDB/CAD |
| Nominal distance | 15.567 LD (≈ 5,983,915 km, 0.04 au) |
| Relative velocity | 56.70 km/s (v∞ 56.70 km/s) — unusually fast for a near-Earth asteroid |
| Modeled Earth MOID | 0.04 au (Scout preliminary estimate) |
| Eccentricity (sampled) | 0.997 – 1.000 (near-parabolic) |
| Inclination (sampled) | 109.00° – 109.03° (retrograde) |
| Absolute magnitude (H) | 11.7 |
| Estimated diameter | ≈ 12–27 km (nominal ≈ 16 km), H-derived |
| Observations / arc | 9 observations across 743.04 days |
| Positional uncertainty | 0.41 arcmin (current fit) · 0.43 arcmin (1-day propagation) |
| Scout scores | NEO 100 · PHA 100 · Geocentric 0 · Tisserand 100 (Scout's internal 0–100 indicators, not raw orbital elements) |
| Sentry status | Not listed (awaiting a confirmed orbit) |
| Hazard level | Scout PHA-class flag; 0.0% of 300 sampled orbits show an impact flag |
All values above are taken directly from the Scout NEOCP record. Astrophyzix has not added any derived orbital elements here, since e ≈ 1 makes a standard a/q/Q solution unreliable at this stage.
SWAN26Q Close-Approach Overview
| Date/Time (UTC) | Body | Nominal distance | MOID | Vrel (km/s) |
|---|---|---|---|---|
| 2026-09-16 18:24 (last Scout run) | Earth | 0.04 au 15.567 LD | 0.04 au | 56.70 |
Scout reports a single distance value here rather than a min–max range in AU — the real uncertainty on this object lives in its orbital elements (see Sampled Orbit Cloud above), not in a distance spread.
1. Object SWAN26Q
An unconfirmed, likely long-period object with a near-parabolic, retrograde orbit and a large (double-digit kilometre) size estimate. Currently far from Earth by close-approach standards (15.6 LD) with no impact signal in its sampled orbit family, but flagged PHA-class by Scout pending a firmer orbit.
Why this orbit doesn't fit the usual Apollo/Aten/Amor picture
Every other object in Astrophyzix's recent reports has had a well-defined semi-major axis and a clean NEO classification. SWAN26Q's sampled orbits sit at e ≈ 0.998, right at the edge between a very long-period ellipse and an unbound (hyperbolic) trajectory. Combined with an inclination of 109° — retrograde, meaning it orbits the Sun opposite to the planets — this is a signature far more common among long-period comets than main-belt-sourced asteroids. The SWAN prefix in the designation is also historically associated with comet discoveries made using the SOHO spacecraft's SWAN (Solar Wind ANisotropies) instrument, which supports that reading, though this report treats it as unconfirmed rather than asserting a cometary nature outright.
Interpretation of the Current Data
A 743-day observation arc sounds long, but with only 9 total observations it is a sparse, not a dense, arc — likely a handful of detections around each of a few brief observing windows, consistent with an object that spends much of its time too close to the Sun in our sky to track (its current solar elongation is just 14°).
The 0.0% impact-flag rate across 300 sampled orbits is a meaningful, positive signal at this stage: even accounting for the full spread of plausible orbits Scout has fit, none currently point toward an Earth impact. That figure is expected to firm up (and stay at or near zero) as new observations arrive once the object clears the Sun's glare.
Astrophyzix Assessment:
SWAN26Q is a preliminary, unconfirmed Scout NEOCP object that warrants continued monitoring rather than concern. Its PHA-class flag reflects an automated, conservative screening threshold applied to any large object with a small modeled MOID and a short arc — not a confirmed hazard. Follow-up astrometry, likely once solar elongation improves, will determine whether it graduates to a confirmed JPL orbit or is later reclassified.
Astrophyzix Risk Index (ARI)
60 / 100 for SWAN26Q — the highest of any object in Astrophyzix's recent tracked set, driven by its large size estimate and PHA-class flag rather than by proximity (it is currently over 15 lunar distances away).
ARI is an Astrophyzix composite index used to rank objects at a glance. It is not an official NASA, ESA or IAU hazard rating, and for an unconfirmed Scout object like this one it should be read as provisional. The authoritative sources are Sentry (confirmed impact monitoring) and Scout (preliminary NEOCP triage, used here).
Astrophyzix Digital Observatory Interpretation and FAQ
1. Why does this report look different from Astrophyzix's other asteroid reports?
Other recent reports (2026 SY2, 2026 SC, 2026 SA8) covered confirmed objects with full JPL orbital solutions. SWAN26Q is still on the Minor Planet Center's Near-Earth Object Confirmation Page (NEOCP) — an unconfirmed candidate being triaged by NASA's Scout system, with a much sparser, less certain data set.
2. What does "PHA-class" mean here if it isn't Sentry-confirmed?
Scout assigns a phaScore (here, 100 out of 100) based on the object's estimated size and modeled MOID, using the same size/distance criteria as the official PHA definition. It's a fast, automated early-warning flag designed to prioritize follow-up observations — not the same as a Sentry impact-risk listing, which requires a confirmed multi-observation orbit.
3. Why is the eccentricity so close to 1?
An eccentricity of 1 marks the boundary between a bound, elliptical orbit and an unbound, parabolic or hyperbolic trajectory. Sampled values of 0.997–1.000 mean the current data can't yet rule out either possibility — consistent with an object making a single, long-period passage through the inner solar system rather than a repeating short-period orbit.
4. Why is the inclination around 109°?
Inclinations above 90° indicate a retrograde orbit — the object circles the Sun in the opposite direction to the planets. This is unusual for asteroids but common among long-period comets, which can arrive from any direction and inclination.
5. Is SWAN26Q dangerous?
Based on current data, no impact trajectory is indicated: it is presently over 15 lunar distances away, and none of the 300 orbits Scout has sampled from the observation arc show an Earth-impact flag. The PHA-class label reflects its size and preliminary MOID, not a confirmed threat.
6. What happens next?
As SWAN26Q's solar elongation improves, new observations should extend the arc, tighten the eccentricity and inclination estimates, and may allow it to graduate to a confirmed JPL orbit — or be reclassified if further data changes the picture. Astrophyzix will update this profile once a confirmed CAD/SBDB solution or a Sentry entry becomes available.
Track live: Astrophyzix Live Orbital Viewer
Risk Assessment
No impact signal in current data.
- 0.0% of 300 Monte Carlo orbit samples from the current fit are flagged as potential Earth impactors.
- Current nominal distance is 15.567 LD — far outside any close-approach concern today.
PHA-class flag, but not Sentry-confirmed.
- Scout's phaScore of 100 reflects its automated screening criteria (large size, small modeled MOID), applied conservatively to a short-arc object.
- SWAN26Q is not yet listed by JPL Sentry, which requires a confirmed orbit.
Significant orbital uncertainty.
- Only 9 observations across a sparse 743-day arc; eccentricity (0.997–1.000) and inclination (109.00–109.03°) are the only elements meaningfully constrained.
- No semi-major axis, perihelion, aphelion or period is reported, since these are unreliable at e ≈ 1.
Size regime, if confirmed.
- At an estimated 12–27 km, this is a far larger object than the metre-scale NEOs in Astrophyzix's typical daily reports — in the general size range associated with major, globally significant impacts in Earth's geological past.
- This context is included for scale only: current data shows no impact geometry, and the object is unconfirmed and far from Earth.
Observational context.
- A solar elongation of 14° currently places SWAN26Q in a difficult observing position near the Sun, limiting new astrometry until its position improves.
Astrophyzix Digital Observatory Scientific Summary
SWAN26Q (NEOCP) is an unconfirmed Scout candidate object, last updated 16 September 2026, based on 9 observations spread across a 743-day arc. Its currently modeled geometry places it 15.567 LD (0.04 au) from Earth, moving at 56.70 km/s — a speed markedly higher than typical near-Earth asteroids, and more characteristic of a long-period or first-time-inbound comet.
Sampled orbits show an eccentricity of 0.997–1.000 (essentially parabolic) and an inclination of about 109° (retrograde), a combination that does not fit the standard Apollo/Aten/Amor classification used elsewhere in Astrophyzix's reporting. With H = 11.7, its estimated diameter is roughly 12–27 km (nominal ≈ 16 km) — substantially larger than the small NEOs typically covered here.
Scout's automated scoring flags SWAN26Q as PHA-class (phaScore 100), reflecting its size and modeled MOID under short-arc conditions; it has not yet been confirmed by JPL or listed by Sentry. Of 300 orbits sampled from the current fit, 0.0% show an Earth-impact flag. From a planetary-defence standpoint, SWAN26Q is a preliminary, closely-watched object requiring follow-up rather than a confirmed hazard — its status should be expected to firm up considerably once its solar elongation improves and new observations become possible.
Sources
- NASA/JPL Scout — NEOCP Object Triage
- Minor Planet Center — NEO Confirmation Page (NEOCP)
- CNEOS Sentry Impact Monitoring
- NASA/JPL Small-Body Database (pending confirmed listing)
