(See related pages)
Below you will find key words and concepts that you should remember from this chapter.
|
|
|
| asteroid | Relatively small, rocky bodies that orbit the Sun. Most asteroids orbit the Sun between the planets Mars and Jupiter and range in size from 1,000 km diameter to just a few meters. (See page(s) 552) |
| |
| |
| |
| astronomical unit | A unit of measure devised by convenience by astronomers to describe the distance from the Sun of objects in the Solar System. One astronomical unit (A.U.) is equal to the average distance of Earth from the Sun (150,000,000 km or about 93.5 million miles). (See page(s) 554) |
| |
| |
| |
| comet | Small celestial objects composed of ice, dust, and rocky debris that orbit the Sun in outermost regions of the Solar System known as the Oort cloud and the Kuiper Belt. (See page(s) 552) |
| |
| |
| |
| dark matter | Matter occurring throughout the Universe that cannot be seen with available technologies. Astronomers hypothesize the existence of this matter to account for observed effects of gravity in the Universe. (See page(s) 554) |
| |
| |
| |
| greenhouse effect | Term used to describe the phenomenon whereby a planet's atmosphere absorbs radiant energy, causing the surface temperature to be higher than it would be without an atmosphere. (See page(s) 565) |
| |
| |
| |
| inner planet | Also known as the terrestrial planets, these are the planets in our Solar System composed principally of silicate materials (Mercury, Venus, Earth, and Mars, as well as the Moon and the two Martian satellites). (See page(s) 551) |
| |
| |
| |
| meteor | The glowing trail of hot gas and vaporized debris left by a solid object heated by friction as it moves through the Earth's atmosphere. (See page(s) 575) |
| |
| |
| |
| meteorite | Small fragments of Solar System material composed of iron, rock, or stony-iron that survive re-entry into Earth's atmosphere and impact with Earth's surface. (See page(s) 576) |
| |
| |
| |
| Milky Way galaxy | A large cluster of perhaps 100 billion stars and their associated planetary systems of which our Solar System is one. (See page(s) 554) |
| |
| |
| |
| outer planet | Term given to those planets of our Solar System composed principally of gases or frozen material (gas or liquid) of various composition. These include Jupiter, Saturn, Unranus, and Neptune. (See page(s) 551) |
| |
| |
| |
| planet | Any relatively large solid or gaseous body orbiting a star. (See page(s) 550) |
| |
| |
| |
| planetesimal | Small aggregations of rocky and gaseous matter that coalesce from the solar nebula due to gravitational collapse. These small bodies may collide and congeal to form larger bodies that become planets. (See page(s) 556) |
| |
| |
| |
| solar nebula | A rotating, flattened disc of dust and gas that may differentiate into stars and planets due to gravitational collapse. (See page(s) 554) |
| |
| |
| |
| solar system | Any cluster of planets, asteroids, comets orbiting a central star. (See page(s) 550) |
| |
| |
| |
| solar wind | An outflow of gas and charged particles streaming outward from the Sun into space. (See page(s) 578) |
| |
| |
| |
| star | A large ball of gas that has collapsed due to gravity and in which gravitational energy has initiated atomic fusion reactions thus emitting enormous quantities of energy to space. (See page(s) 550) |
| |
| |
| |
| Universe | Term used to describe the collection of all matter that is known to exist. (See page(s) 554) |