811221
811221 belongs to the Apollo group of near-Earth asteroids, whose orbits cross the path of Earth; with a semi-major axis of 2.083 AU it takes 3.01 yr to circle the Sun.
Orbit and dynamics
The path is an ellipse reaching 1.008 AU from the Sun at perihelion and 3.158 AU at aphelion, a radial span of 2.15 AU.
Applying Kepler's third law to a = 2.083 AU gives an orbital period of 3.01 yr, or about 1,098 days.
The high eccentricity (0.516) produces a strongly elongated orbit, so the object spends most of its time far from the Sun.
The orbital plane is tilted 5.26° relative to the ecliptic.
By the vis-viva equation its orbital speed rises to 36.5 km/s at perihelion and falls to 11.7 km/s at aphelion.
Size and surface
No direct size measurement is available; from an absolute magnitude of H = 22.58 and an assumed geometric albedo of 0.14, the diameter works out to roughly 0.11 km.
Observation record and orbit quality
The current orbit solution is based on 327 observations and has a weighted RMS residual of 0.3876 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.
