COMETS
Text Reference: Arny, 305-313
NAME: _____________________________
1. On the diagram, label the head, tail, nucleus, and coma. Add the dimensions.
2. The nucleus of the comet is made of:
3. The nucleus is sometimes referred to as an ___________________ or a
__________________ ___________________ .
4. The density of the nucleus is estimated to be ____________ g/cc, so it is probably
_________________ like snow.
5. Spectra of the gas show it is rich in _____________, _______________ and
___________________ .
6. Most comets are surrounded by a huge cloud of hydrogen, because evaporating water is split apart by the sun’s ___________ radiation.
7. Most comets come from the ___________________ Cloud (from beyond Pluto (40 AU) out to
150,000AU away. This collection of comets is assumed to surround the sun, since many of them approach at angles not in line with the orbit of the planets. As shown in figure 10.14, they are shifting into an orbit that takes the toward the sun by the gravity of:
8. Comets that approach the sun more in line with the main plane of the SS are thought to come from the ______________ Belt, which extends from Neptune (30AU) out to about 50AU.

9. The nucleus of the comet will begin to vaporize when it gets about ______AU from the sun, about as far away as the planet ______________ .
10. The tail of a comet is vaporized gas that is pushed away from the nucleus by matter and energy from the sun.
Comets actually have two tails. The dust tail is directed by __________________ pressure (photons of light).
The gas tail is directed by the _____________ _____________--atoms of H and He that stream away from the sun’s upper atmosphere.
11. Because both the atoms and the photons are produced by the sun
, comets’ tails always
(figures 10.16 and 10.17):
12. Dust particles in the tail are visible because they ______________ visible light from the sun.
Gas particles emit their own light through the process of: ______________________ .
13. _____________ _____________ comets are those which reappear in intervals less than 200 years.
14. When all of the gaseous matter making up a comet has vaporized, the solid particles will continue to follow the original orbit. Since these bits of cosmic debris are outside of the Earth’s atmosphere, they are called a _________________ swarm.
When the swarm intersects with the Earth’s atmosphere, the particles will vaporize. This event is referred to as a ___________________ shower.