Science.7.9.A

Planets: The International Astronomical Unit has declared, independently of the formal definition of planet, that there are eight planets in the Solar System. In the geological definition used by most planetologists, a planet is a rounded sub-stellar body, possibly a satellite.

Meteors: When a meteoroid, comet, or asteroid enters Earth's atmosphere, aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it leaves in its wake. This phenomenon is called a meteor or shooting star. Most meteors are fragments from comets or asteroids, while others are collision impact debris ejected from bodies such as the Moon or Mars.

Asteroids:  The term asteroid generally refers to the minor planets of the inner Solar System, including those co-orbital with Jupiter. Larger asteroids are often called planetoids.

Comets: Comets originate in the Kuiper Belt or the Oort Cloud. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma and tail of a comet are caused by the effects of solar radiation and the solar wind acting upon the nucleus of the comet.

Kuiper Belt: Most Kuiper Belt objects are composed largely of frozen volatiles (termed ices) such as methane, ammonia, and water. The Kuiper Belt is home to most of the objects that astronomers generally accept as dwarf planets: Orcus, Pluto, Haumea, Quaoar, and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region.

Oort Cloud: The outer Oort Cloud is only loosely bound to the Solar System and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way itself. These forces occasionally dislodge comets from their orbits within the cloud and send them toward the inner Solar System.