Key Facts


161P/Hartley-IRAS 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 161P/Hartley-IRAS 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.

161P/Hartley-IRAS orbits the sun every 7,840 days (21.46 years), coming as close as 1.27 AU and reaching as far as 14.17 AU from the sun. Its orbit is highly elliptical. Based on its brightness and the way it reflects light, 161P/Hartley-IRAS 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

161P/Hartley-IRAS's orbit is 0.45 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

161P/Hartley-IRAS's orbit is determined by observations dating back to Dec. 29, 1983. It was last officially observed on Oct. 12, 2005. The IAU Minor Planet Center records 321 observations used to determine its orbit.

Accessibility and Exploration

This comet 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 161P/Hartley-IRAS:



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Orbital Elements

  • Epoch: 2452749.5 JD
  • Semi-major axis: 7.721 AU
  • Eccentricity: 0.8351
  • Inclination: 95.7°
  • Longitude of Ascending Node: 1.42°
  • Argument of Periapsis: 47.14°
  • Mean Anomaly: 323.58°

Physical Characteristics

  • Diameter: ~3431.463 km
  • Magnitude: 11.4

Derived Characteristics

  • Orbit Period: 7,840 days (21.46 years)
  • Avg. Orbit Speed: 10.71 km/s
  • Aphelion Distance: 14.17 AU
  • Perihelion Distance: 1.27 AU

Map Comparison

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Orbit Simulation

Sky Map

The position of 161P/Hartley-IRAS 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.