Key Facts


C/1917 F1 (Mellish) is a large comet with a medium-length orbit that is highly inclined to the ecliptic plane of the solar system. NASA JPL has classified Mellish 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.

Mellish orbits the sun every 53,000 days (145.11 years), coming as close as 0.19 AU and reaching as far as 55.11 AU from the sun. Its orbit is highly elliptical. Based on its brightness and the way it reflects light, Mellish is probably between 2658.000 to 5943.469 kilometers in diameter, making it the largest asteroid/dwarf planet, very roughly comparable in size to the U.S. state of Alaska.

No Close Approaches

Mellish's orbit is 0.00 AU from Earth's orbit at its closest point. This means that its orbit is very close to Earth's orbit.

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

Images and Observations

Mellish's orbit is determined by observations dating back to March 21, 1917. It was last officially observed on June 25, 1917. The IAU Minor Planet Center records 170 observations used to determine its orbit.

Accessibility and Exploration

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



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Orbital Elements

  • Epoch: 2421333.5 JD
  • Semi-major axis: 27.65 AU
  • Eccentricity: 0.9931
  • Inclination: 32.68°
  • Longitude of Ascending Node: 88.67°
  • Argument of Periapsis: 121.32°
  • Mean Anomaly: 0.03°

Physical Characteristics

  • Diameter: ~3431.463 km

Derived Characteristics

  • Orbit Period: 53,000 days (145.11 years)
  • Avg. Orbit Speed: 5.68 km/s
  • Aphelion Distance: 55.11 AU
  • Perihelion Distance: 0.19 AU

Map Comparison

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Orbit Simulation

Sky Map

The position of C/1917 F1 (Mellish) 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.