SpaceAtlas Space Object Data
NASA JPL SBDB · 2021 SP4

2021 SP4

2021 SP4 belongs to the Apollo group of near-Earth asteroids, whose orbits cross the path of Earth; with a semi-major axis of 1.468 AU it takes 1.78 yr to circle the Sun.

Apollo Observations: 166
Orbital Period · P
1.78 yr
v(q)
37.8 km/s
v(Q)
16 km/s
Diameter · ≈
0.23 km
TJ
4.5
Eccentricity · e
0.4051

Orbit and dynamics

Between its closest point (0.873 AU) and its farthest (2.063 AU), the heliocentric distance changes by 1.19 AU over every revolution.

One full revolution takes 1.78 yr (650 days), computed from the semi-major axis of 1.468 AU.

The high eccentricity (0.405) produces a strongly elongated orbit, so the object spends most of its time far from the Sun.

The orbital plane is tilted 9.92° relative to the ecliptic.

By the vis-viva equation its orbital speed rises to 37.8 km/s at perihelion and falls to 16 km/s at aphelion.

Because q < 1 AU and Q > 1 AU, this orbit geometrically intersects the region of Earth's orbit.

Size and surface

No direct size measurement is available; from an absolute magnitude of H = 20.96 and an assumed geometric albedo of 0.14, the diameter works out to roughly 0.23 km.

Observation record and orbit quality

Astrometry from 166 individual observations underpins this orbit; the fit leaves an RMS residual of 0.5999 arcseconds.

Condition code U = 0 means the orbit is very well determined, leaving only a small uncertainty in the future ephemeris.

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
1.468 AU
Eccentricity
0.4051
Perihelion
0.873 AU
Aphelion
2.062687 AU
Inclination
9.92°
Orbital Period
— yr
Epoch
2461200.5
Mean Anomaly
164.43°

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
2029-Apr-19 13:14 0.469951 AU
70303673 km
23.22 km/s
2038-Jan-30 19:44 0.142803 AU
21363020 km
9.05 km/s
2045-Apr-19 16:03 0.468808 AU
70132605 km
23.19 km/s
2054-Jan-29 12:05 0.144294 AU
21586108 km
9.05 km/s
2061-Apr-19 03:38 0.458999 AU
68665250 km
22.89 km/s
2070-Jan-26 04:53 0.148346 AU
22192261 km
9.05 km/s
2077-Apr-18 04:02 0.440021 AU
65826242 km
22.31 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
20.96

Orbit Quality

RMS
0.59992
Condition
0
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.