Key Facts


Ismene is a large asteroid that orbits between Mars and Jupiter in the outer reaches of the main asteroid belt. NASA JPL has not classified Ismene as potentially hazardous because its orbit does not bring it close to Earth.

Ismene orbits the sun every 2,920 days (7.99 years), coming as close as 3.32 AU and reaching as far as 4.67 AU from the sun. Ismene is about 159.0 kilometers in diameter, making it larger than 99% of asteroids, comparable in size to the U.S. state of Vermont.

The rotation of Ismene has been observed. It completes a rotation on its axis every 6.52 hours.

Ismene's spectral type P (Tholen) / X (SMASSII) indicates that it is likely to contain iron, nickel, and cobalt.

No Close Approaches

Ismene's orbit is 2.35 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

Ismene's orbit is determined by observations dating back to Nov. 6, 1894. It was last officially observed on July 4, 2023. The IAU Minor Planet Center records 10,730 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 Ismene:



   or view a random object

Orbital Elements

  • Epoch: 2460200.5 JD
  • Semi-major axis: 3.994 AU
  • Eccentricity: 0.1682
  • Inclination: 6.18°
  • Longitude of Ascending Node: 175.44°
  • Argument of Periapsis: 271.17°
  • Mean Anomaly: 97.11°

Physical Characteristics

  • Diameter: 159.00000 km
  • Magnitude: 7.94
  • Albedo: 0.066
  • Spectral type (Tholen): P
  • Spectral type (SMASS): X

Derived Characteristics

  • Orbit Period: 2,920 days (7.99 years)
  • Avg. Orbit Speed: 14.88 km/s
  • Aphelion Distance: 4.67 AU
  • Perihelion Distance: 3.32 AU
  • Rotation Period: 6.52 hours
  • Approx. Composition: iron, nickel, and cobalt.

Map Comparison

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Orbit Simulation

Sky Map

The position of Ismene 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.