SpaceAtlas Space Object Data
NASA JPL SBDB · 2021 HM

2021 HM

2021 HM belongs to the Apollo group of near-Earth asteroids, whose orbits cross the path of Earth; with a semi-major axis of 1.802 AU it takes 2.42 yr to circle the Sun.

Apollo Observations: 149
Orbital Period · P
2.42 yr
v(q)
35.6 km/s
v(Q)
13.8 km/s
Diameter · ≈
0.03 km
TJ
3.94
Eccentricity · e
0.4411

Orbit and dynamics

The path is an ellipse reaching 1.007 AU from the Sun at perihelion and 2.597 AU at aphelion, a radial span of 1.59 AU.

Applying Kepler's third law to a = 1.802 AU gives an orbital period of 2.42 yr, or about 884 days.

The high eccentricity (0.441) produces a strongly elongated orbit, so the object spends most of its time far from the Sun.

Its inclination of 4.93° keeps it close to the plane of the ecliptic.

By the vis-viva equation its orbital speed rises to 35.6 km/s at perihelion and falls to 13.8 km/s at aphelion.

Size and surface

No direct size measurement is available; from an absolute magnitude of H = 25.5 and an assumed geometric albedo of 0.14, the diameter works out to roughly 0.03 km.

Observation record and orbit quality

The current orbit solution is based on 149 observations and has a weighted RMS residual of 0.461 arcseconds.

Condition code U = 5 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
1.802 AU
Eccentricity
0.4411
Perihelion
1.007 AU
Aphelion
2.596862 AU
Inclination
4.93°
Orbital Period
— yr
Epoch
2461200.5
Mean Anomaly
46.32°

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
2038-Feb-22 22:23 0.347780 AU
52027104 km
17.87 km/s
2050-May-15 21:10 0.030704 AU
4593198 km
8.32 km/s
2067-Mar-12 14:11 0.125382 AU
18756906 km
10.64 km/s
2079-Jun-12 12:35 0.282023 AU
42190052 km
16.77 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
25.5

Orbit Quality

RMS
0.46102
Condition
5
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

Explore asteroids, comets and near-Earth objects with JPL orbital data.