SpaceAtlas Space Object Data
NASA JPL SBDB · 2021 WD4

2021 WD4

2021 WD4 is an Amor-type near-Earth asteroid that approaches Earth from beyond our orbit without crossing it, orbiting the Sun at 1.418 AU once every 1.69 yr.

Amor Observations: 35
Orbital Period · P
1.69 yr
v(q)
31.5 km/s
v(Q)
19.9 km/s
Diameter · ≈
0.09 km
TJ
4.63
Eccentricity · e
0.227

Orbit and dynamics

The path is an ellipse reaching 1.096 AU from the Sun at perihelion and 1.74 AU at aphelion, a radial span of 0.644 AU.

Applying Kepler's third law to a = 1.418 AU gives an orbital period of 1.69 yr, or about 617 days.

An eccentricity of 0.227 makes the orbit moderately elongated.

The orbital plane is tilted 19.58° relative to the ecliptic.

By the vis-viva equation its orbital speed rises to 31.5 km/s at perihelion and falls to 19.9 km/s at aphelion.

Its perihelion lies just outside Earth's orbit, which is why it is classed as Earth-approaching rather than Earth-crossing.

Size and surface

No direct size measurement is available; from an absolute magnitude of H = 23.06 and an assumed geometric albedo of 0.14, the diameter works out to roughly 0.09 km.

Observation record and orbit quality

The current orbit solution is based on 35 observations and has a weighted RMS residual of 0.446 arcseconds.

Condition code U = 6 indicates a moderately constrained orbit; predictions decades ahead still carry noticeable uncertainty.

About these computed values

Orbital periods, perihelion and aphelion speeds, and diameter estimates on this page are computed by SpaceAtlas from the JPL SBDB orbital elements. They are derived quantities, not values copied from the source catalogue.

Orbital Parameters

Semi-Major Axis
1.418 AU
Eccentricity
0.227
Perihelion
1.096 AU
Aphelion
1.739886 AU
Inclination
19.58°
Orbital Period
— yr
Epoch
2461200.5
Mean Anomaly
216.56°

Orbit diagram

The Sun sits at the focus (orange). Earth's orbit is the grey circle at 1 AU. The red dot marks the object's position at the catalog epoch.

3D orbit (interactive)

Drag to rotate; scroll or pinch to zoom. The Sun is at the focus (orange), Earth's orbit is the grey ring at 1 AU, and the red dot marks the object's current position.

Close approaches

Predicted close approaches to Earth, from NASA's Center for Near-Earth Object Studies (CNEOS).

Date (UTC)Miss distanceVelocity
2039-Apr-17 01:17 0.490128 AU
73322124 km
9.09 km/s
2043-Dec-08 23:35 0.149529 AU
22369240 km
11.89 km/s
2048-Dec-02 04:58 0.262134 AU
39214746 km
10.49 km/s
2065-Dec-06 04:02 0.303480 AU
45400004 km
17.05 km/s
2070-Dec-08 17:17 0.142803 AU
21363067 km
10.99 km/s

Distances in astronomical units (AU) and kilometres. Source: NASA/JPL CNEOS Close Approach Data API.

Physical Parameters

Diameter
— km
Albedo
—
Density
— g/cm³
Rotation Period
— h
Absolute Magnitude
23.06

Orbit Quality

RMS
0.44601
Condition
6
Orbit ID
—
Data source: NASA JPL Small-Body Database · NASA CNEOS. Orbital periods, perihelion and aphelion speeds, and diameter estimates on this page are computed by SpaceAtlas from the JPL SBDB orbital elements. They are derived quantities, not values copied from the source catalogue.

Keep exploring

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