Key Facts

  • Categorized as a Halley-type Comet
  • Comparable in size to the city of Indianapolis (26.00 km diameter)
  • Will pass within 22,944,892 km of Earth in 2126
  • Classified as a Near Earth Asteroid (NEA)
  • Not a Potentially Hazardous Object
  • See orbit simulation


109P/Swift-Tuttle 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 109P/Swift-Tuttle 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.

109P/Swift-Tuttle orbits the sun every 48,700 days (133.33 years), coming as close as 0.96 AU and reaching as far as 51.22 AU from the sun. Its orbit is highly elliptical. 109P/Swift-Tuttle is about 26.0 kilometers in diameter, making it larger than 99% of asteroids, comparable in size to the city of Indianapolis.

Close Approaches

109P/Swift-Tuttle'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.

109P/Swift-Tuttle has 1 close approaches predicted in the coming decades:

Date Distance from Earth (km) Velocity (km/s)
Aug. 5, 2126 22,944,892 58.340

Images and Observations

109P/Swift-Tuttle's orbit is determined by observations dating back to July 8, 1737. It was last officially observed on March 29, 1995. The IAU Minor Planet Center records 652 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: 2450000.5 JD
  • Semi-major axis: 26.09 AU
  • Eccentricity: 0.9632
  • Inclination: 113.45°
  • Longitude of Ascending Node: 139.38°
  • Argument of Periapsis: 152.98°
  • Mean Anomaly: 7.63°

Physical Characteristics

  • Diameter: 26.00000 km
  • Magnitude: 4.5

Derived Characteristics

  • Orbit Period: 48,700 days (133.33 years)
  • Avg. Orbit Speed: 5.83 km/s
  • Aphelion Distance: 51.22 AU
  • Perihelion Distance: 0.96 AU

Map Comparison

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Orbit Simulation

Sky Map

The position of 109P/Swift-Tuttle 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.