8.9 Key Terms
Asteroids are tiny, rocky bodies that orbit the Sun. 8.7
Asteroid Belt: a region between the orbits of Mars and Jupiter where the majority of asteroids are found. 8.7
Coma: a comet’s temporary atmosphere of gas and dust illuminated by sunlight. 8.8
Comet: a relatively small chunk of icy material (typically a few kilometres across) that develops an atmosphere as it approaches the Sun. 8.8
Ceres is the most massive object in the asteroid belt. 8.6
Differentiated: to be separated into layers of different density materials. 8.1
Eris is the most widely-known dwarf planet in the solar system, which is roughly 27 percent more massive than Pluto. 8.6
Kuiper Belt is a region beyond the orbit of Neptune at 30 Astronomical Units (AU) to about 50 AU from the sun. 8.5
Kuiper Belt Objects (KBOs): objects composed of rock and metal, like the asteroids, but also frozen ices like ammonia, methane, and water. 8.5
Long-period comets: comets with orbital periods longer than about a century. 8.8
Makemake is the third largest and second brightest dwarf planet we have discovered so far. 8.6
Meteorite: a large meteoroid formed from an asteroid that strikes the Earth’s surface. 8.7
Nucleus (of a comet): the real source of a comet, which is the fragment of ancient icy material responsible for the atmosphere and the tail. 8.8
Occultation: the passage of one astronomical object in front of another. 8.3
Oort Cloud: a hypothesized spherical cloud of icy objects up to 50,000 AU from the sun. 8.5
Oort Cloud Object (OCO): name that would be given to any object found in the Oort Cloud. 8.5
Shepherd moons: moons whose gravitation serves to “shepherd” the ring particles and keep them confined to a narrow ribbon; examples include two of Saturn’s moons: Pandora and Prometheus. 8.3
Short-period comets: comets with orbital periods shorter than about a century. 8.8
Tidal force: the result from the unequal gravitational pull on two sides of a body. 8.1
Trans-Neptunian Objects (TNO) are any solar system minor planet that orbits the sun at a greater average distance than Neptune. 8.5
