Comet
- Small bodies
- Rocks with ice either at the surface or beneath the surface
- Remnants from the formation of the Solar System
- At 20 AU the tails and coma start becoming visible
- Irregular shapes
- Not enough mass to become spherical
- Don't last forever
Nucleus

- Visible coma
- Fuzzy atmosphere around comet
- Halo of gas, ice, and rock
- Effects of solar radiation upon the comet's nucleus
- Nuclei are loose collections of ice, dust, and small rocky particles a few km in size
- Tail
- Dust tail
- Brightest part of the tail
- Ion tail
- Ionized gas
- Carried outward by streams of ions emitted by the Sun
- Pushed directly outward from the Sun
Astronomy Space