Key Facts

  • Categorized as a Main-belt Asteroid
  • Comparable in size to the U.S. state of Rhode Island (50.14 km diameter)
  • Not a Near Earth Object
  • Not a Potentially Hazardous Object
  • See orbit simulation


Amalthea is a large asteroid orbiting between Mars and Jupiter in the main portion of the asteroid belt. NASA JPL has not classified Amalthea as potentially hazardous because its orbit does not bring it close to Earth.

Amalthea orbits the sun every 1,340 days (3.67 years), coming as close as 2.17 AU and reaching as far as 2.58 AU from the sun. Amalthea is about 50.1 kilometers in diameter, making it larger than 99% of asteroids, comparable in size to the U.S. state of Rhode Island.

The rotation of Amalthea has been observed. It completes a rotation on its axis every 9.95 hours.

Amalthea's spectral type S (Tholen) / S (SMASSII) indicates that it is likely to contain and .

No Close Approaches

Amalthea's orbit is 1.18 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

Amalthea's orbit is determined by observations dating back to March 12, 1871. It was last officially observed on July 7, 2022. The IAU Minor Planet Center records 3,732 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 Amalthea:



   or view a random object

Orbital Elements

  • Epoch: 2459800.5 JD
  • Semi-major axis: 2.376 AU
  • Eccentricity: 0.0861
  • Inclination: 5.04°
  • Longitude of Ascending Node: 123.44°
  • Argument of Periapsis: 78.74°
  • Mean Anomaly: 98.91°

Physical Characteristics

  • Diameter: 50.13700 km
  • Magnitude: 8.66
  • Albedo: 0.224
  • Spectral type (Tholen): S
  • Spectral type (SMASS): S

Derived Characteristics

  • Orbit Period: 1,340 days (3.67 years)
  • Avg. Orbit Speed: 19.29 km/s
  • Aphelion Distance: 2.58 AU
  • Perihelion Distance: 2.17 AU
  • Rotation Period: 9.95 hours
  • Approx. Composition: and .

Map Comparison

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Orbit Simulation

Sky Map

The position of Amalthea 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.