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How to Identify a Comet

Sometimes referred to as dirty snowballs, comets consist of rock, ice and other compounds left over from developing planets and stars. With strongly elliptical orbits that orbit the sun, comets show visible tails as their orbit brings them close to the sun. Many comets pass around the sun just once, but others like Halley's Comet show up regularly. Follow these steps to identify a comet.

Instructions

- 1
  Travel away from city lights that obscure views of comets. Dark, clear nights with no moonlight work best for seeing comets in the sky.
- 2
  Look for a fuzzy ball. Comets contain a small, bright nucleus in the middle, but then are surrounded by a much larger (up to 1 million kilometers in diameter) cloud called a coma. The coma grows as it nears the sun. Together, the nucleus and coma make up the head of a comet.
- 3
  Understand that your chances of seeing a comet increase as it approaches the sun. Just as the reflection of sunlight makes it possible for you to see the Moon and nearby planets, it also makes a comet more visible. As the comet moves closer to the sun, its gases absorb the radiation from the sun for an even brighter comet.
- 4
  Check for a tail. As the comet approaches the sun, tails become more apparent, particularly ones that are 100 million km. or longer. When the ice of the comet evaporates because of the heat of the sun, the gas and dust from the comet gets pushed away and forms tails. The comet's gases form a plasma or ion tail that appears straight and blue in color. When dust is pushed away, a dust tail forms. The more noticeable white or yellow dust tails tend to either curve or look like a fan.
- 5
  Monitor changes in a comet from night to night if you have access to a telescope. The comet's shape can change or it may adopt streamers because of eruptions in the nucleus.

Astronomy