31221
31221 is an Amor-type near-Earth asteroid that approaches Earth from beyond our orbit without crossing it, orbiting the Sun at 1.723 AU once every 2.26 yr.
Orbit and dynamics
The path is an ellipse reaching 1.28 AU from the Sun at perihelion and 2.166 AU at aphelion, a radial span of 0.886 AU.
Applying Kepler's third law to a = 1.723 AU gives an orbital period of 2.26 yr, or about 826 days.
An eccentricity of 0.257 makes the orbit moderately elongated.
A steep inclination of 20.22° carries it well above and below the ecliptic plane.
By the vis-viva equation its orbital speed rises to 29.5 km/s at perihelion and falls to 17.4 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 = 17.23 and an assumed geometric albedo of 0.14, the diameter works out to roughly 1.27 km.
Observation record and orbit quality
The current orbit solution is based on 1,389 observations and has a weighted RMS residual of 0.4873 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
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
No close approaches to Earth are currently on record for this object.
