Key Facts


Comet C/1861 G1 (Thatcher) is an object whose orbit does not match any defined comet orbit class. NASA JPL has not classified Thatcher as potentially hazardous because its orbit does not bring it close to Earth.

Thatcher orbits the sun every 152,000 days (416.15 years), coming as close as 0.92 AU and reaching as far as 110.44 AU from the sun. Its orbit is highly elliptical.

No Close Approaches

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

Images and Observations

Thatcher's orbit is determined by observations dating back to April 11, 1861. It was last officially observed on Sept. 7, 1861. The IAU Minor Planet Center records 187 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 Thatcher:



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Orbital Elements

  • Epoch: 2400920.5 JD
  • Semi-major axis: 55.68 AU
  • Eccentricity: 0.9835
  • Inclination: 79.77°
  • Longitude of Ascending Node: 31.87°
  • Argument of Periapsis: 213.45°
  • Mean Anomaly: -0.02°

Physical Characteristics

Derived Characteristics

  • Orbit Period: 152,000 days (416.15 years)
  • Avg. Orbit Speed: 3.99 km/s
  • Aphelion Distance: 110.44 AU
  • Perihelion Distance: 0.92 AU

Orbit Simulation

Sky Map

The position of C/1861 G1 (Thatcher) 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.