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How to Calculate Cometary Orbits

Most comets travel in extremely elliptical orbits through our solar system. As a result, they only rarely pass close enough to the Earth for easy observation. Astronomers therefore need a way to figure out where a comet will be at any point in the distant future. You can accomplish this task by calculating cometary orbits from a small number of orbital elements. These elements come from observations of the comet in question and give you all the information you need.

Things You'll Need

Cometary orbit elements
Orbit calculation equations
Calculator
Star chart

Instructions

- 1
  Gather the necessary orbit elements for your comet. You need to know the inclination between the orbit and the ecliptic (the plane of the Earth's orbit), the position on the orbit where the comet travels from below the ecliptic to above it, the comet's position when closest to the Sun, the semi-major axis of the orbit, the daily motion of the comet, the eccentricity of the orbit and the position of the comet when these elements were determined.
- 2
  Determine where the comet is along its orbit. You need this to find a new position for the comet. You can determine the location with the number of days since the comet's observation, the comet's anomaly (the result of an elliptical orbit instead of a circular orbit) and the radius vector (distance to the ellipse's focus) of the comet.
- 3
  Find the position of the comet with respect to the plane of the ecliptic. The above calculations find the absolute position of the comet.
- 4
  Find the position of the Earth with respect to the plane of the ecliptic. This way, you can find the position of the comet with respect to the Earth.
- 5
  Calculate the geocentric coordinates from the heliocentric coordinates of the comet.
- 6
  Find the right ascension and declination of the comet from these coordinates. You can compare these to a star chart to find the position of the comet in the sky.

Astronomy