Final answer:
Comets are icy bodies with tails that develop when they near the Sun and do not orbit gas giants. They contain ice, rock, and dust, but not a liquid core, and are different from asteroids. Objects like Pluto are classified as dwarf planets.
Step-by-step explanation:
Comets are small icy objects that contain frozen water, other volatile materials, and solid grains mixed in. They do not contain a liquid core but instead have a nucleus composed of ice, rock, and dust. When comets approach the Sun, they develop tails due to the sublimation of their icy components; this is when solid ice turns directly into gas without becoming liquid first. The two types of comet tails are the ion tail and the dust tail. The ion tail forms when solar wind blows ionized gas away from the comet's nucleus, creating a straight tail that points directly away from the Sun. The dust tail is formed from small solid particles that are swept off the comet's nucleus by solar radiation pressure, resulting in a curved tail.
Comets generally do not orbit gas giants; instead, their orbits can take them from the outer reaches of the solar system, such as the Kuiper belt or Oort cloud, to close passes by the Sun. Objects like Pluto and Eris, which are round due to their gravitational pull and orbit beyond Neptune, are classified as dwarf planets.