Definitions
- Anti-tail.
- Also known as anomalous tail, this occurs when a comet's tail appears to be pointing toward the Sun. Of course, it's not actually pointing toward the sun because comets orbit the Sun. When a comet produces heavy dust particles, they are left along the comet's orbit instead of being pushed away from the Sun.
- Apparition.
- This is the time when a comet is under observation. The term probably comes from the ghostly appearance of comets.
- Coma.
- Also known as the comet's head, the coma is the dense, hazy cloud of water, carbon dioxide, another gases around the comet's nucleus. The head and tail are the only things we see from Earth.
- Dust tail.
- Composed of dust particles from the nucleus and up to 10 million kilometers long, this is the most prominent element of the comet.
- Hydrogen cloud.
- A large, sparse envelope of neutral hydrogen.
- Ion tail.
- Composed of plasma laced with rays and streamers from solar wind, this tail can be several hundred million kilometers long.
- Long-period comets.
- Orbit periods of more than 200 years.
- Nucleus.
- Made up of ice, gas, dust, and small amounts of other materials, this core is solid and stable.
- Outburst.
- A comet sometimes experiences an unexpected increase in brightness for a short time due to the release of dust and gas into the coma from the nucleus. This is known as an outburst.
- Perihelion.
- The point in a comet's orbit when it is closest to the Sun.
- Short-period comets.
- Also known as periodic comets, they have orbit periods of less than 200 years. These coments have a P/ before their name.
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