Key Facts


Zao is a mid-sized asteroid whose orbit approaches the orbit of Earth but does not cross it. NASA JPL has classified Zao as a "Near Earth Asteroid" due to its orbit's proximity to Earth, but it is not considered potentially hazardous because computer simulations have not indicated any imminent likelihood of future collision.

Zao orbits the sun every 1,110 days (3.04 years), coming as close as 1.21 AU and reaching as far as 3.00 AU from the sun. Zao is about 2.3 kilometers in diameter, making it larger than 99% of asteroids, comparable in size to Mount Everest.

The rotation of Zao has been observed. It completes a rotation on its axis every 76.00 hours.

Zao's spectral type None (Tholen) / X (SMASSII) indicates that it is likely to contain iron, nickel, and cobalt.

No Close Approaches

Zao's orbit is 0.24 AU from Earth's orbit at its closest point. This means that there is an wide berth between this asteroid and Earth at all times.

Orbital simulations conducted by NASA JPL's CNEOS do not show any close approaches to Earth.

Images and Observations

Zao's orbit is determined by observations dating back to March 10, 1989. It was last officially observed on Sept. 24, 2021. The IAU Minor Planet Center records 1,714 observations used to determine its orbit.

Accessibility and Exploration

This asteroid is not considered a viable target for human exploration by the NHATS study.

Similar Objects

These objects have orbits that share similar characteristics to the orbit of Zao:



   or view a random object

Orbital Elements

  • Epoch: 2459396.5 JD
  • Semi-major axis: 2.103 AU
  • Eccentricity: 0.4248
  • Inclination: 16.07°
  • Longitude of Ascending Node: 121.65°
  • Argument of Periapsis: 25.43°
  • Mean Anomaly: 224.83°

Physical Characteristics

  • Diameter: 2.30000 km
  • Magnitude: 14.75
  • Albedo: 0.36
  • Spectral type (SMASS): X

Derived Characteristics

  • Orbit Period: 1,110 days (3.04 years)
  • Avg. Orbit Speed: 20.61 km/s
  • Aphelion Distance: 3.00 AU
  • Perihelion Distance: 1.21 AU
  • Rotation Period: 76.00 hours
  • Approx. Composition: iron, nickel, and cobalt.

Map Comparison

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Orbit Simulation

Sky Map

The position of Zao is indicated by a ◯ pink circle. Note that the object may not be in your current field of view. Use the controls below to adjust position, location, and time.

Size Rendering

The above comparison is an artistic rendering that uses available data on the diameter of Zao to create an approximate landscape rendering with Mount Everest in the background. This approximation is built for full-resolution desktop browsers. Shape, color, and texture of asteroid are imagined.