Key Facts


Thereus is a relatively small asteroid with an orbit between Jupiter and Neptune. NASA JPL has not classified Thereus as potentially hazardous because its orbit does not bring it close to Earth.

Thereus orbits the sun every 12,643 days (34.61 years), coming as close as 8.50 AU and reaching as far as 12.74 AU from the sun. Thereus is about 86.5 kilometers in diameter, making it larger than most asteroids, comparable in size to the U.S. state of Delaware.

The rotation of Thereus has been observed. It completes a rotation on its axis every 8.34 days.

No Close Approaches

Thereus's orbit is 7.55 AU from Earth's orbit at its closest point. This means that there is an extremely 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

Thereus's orbit is determined by observations dating back to June 5, 1995. It was last officially observed on Jan. 7, 2018. The IAU Minor Planet Center records 433 observations used to determine its orbit.

Accessibility and Exploration

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



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Orbital Elements

  • Epoch: 2458600.5 JD
  • Semi-major axis: 10.6210557069 AU
  • Eccentricity: 0.199748522681
  • Inclination: 20.3555356399°
  • Longitude of Ascending Node: 205.294746063°
  • Argument of Periapsis: 86.5651767323°
  • Mean Anomaly: 209.741018478°

Physical Characteristics

  • Diameter: 86.50000 km
  • Magnitude: 9.1
  • Albedo: 0.059

Derived Characteristics

  • Orbit Period: 12,643 days (34.61 years)
  • Avg. Orbit Speed: 9.14 km/s
  • Aphelion Distance: 12.74 AU
  • Perihelion Distance: 8.50 AU
  • Rotation Period: 8.34 days

Size Comparison

Orbit Simulation

Sky Map

The position of Thereus 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.