Across
- 4. a small piece of solid matter that enters Earth’s atmosphere and burns up, popularly called a shooting star because it is seen as a small flash of light
- 5. a portion of a meteor that survives passage through the atmosphere and strikes the ground
- 6. a tail consisting of two parts: the dust tail is made of dust loosened by the sublimation of ice in a comet that is then pushed by photons from the Sun into a curved stream; the ion tail is a stream of ionized particles evaporated from a comet and then swept away from the Sun by the solar wind
- 8. chemical changes caused by electromagnetic radiation
- 9. a type of differentiated meteorite that is a blend of nickel-iron and silicate materials
- 12. an Earth-approaching asteroid, one whose orbit could bring it on a collision course with our planet
- 14. the radiation emitted by charged particles being accelerated in magnetic fields and moving at speeds near that of light
- 17. the solid chunk of ice and dust in the head of a comet
- 18. the region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located; the main belt, where the orbits are generally the most stable, extends from 2.2 to 3.3 AU from the Sun
- 20. the heating of a planet or moon’s interior by variable tidal forces caused by changing gravitational pull from a nearby planet or moon
- 21. many meteors appearing to radiate from one point in the sky; produced when Earth passes through a cometary dust stream
Down
- 1. a planet orbiting a star other than our Sun
- 2. a region of space beyond Neptune that is dynamically stable (like the asteroid belt); the source region for most short-period comets
- 3. a small body of icy and dusty matter that revolves about the Sun; when a comet comes near the Sun, some of its material vaporizes, forming a large head of tenuous gas and often a tail
- 7. the gradual accumulation of mass, as by a planet forming from colliding particles in the solar nebula
- 10. an orbital condition in which one object is subject to periodic gravitational perturbations by another, most commonly arising when two objects orbiting a third have periods of revolution that are simple multiples or fractions of each other
- 11. a comet or asteroid whose path intersects the orbit of Earth
- 13. a meteorite composed mostly of stony material, either primitive or differentiated
- 15. a stony or metallic object orbiting the Sun that is smaller than a major planet but that shows no evidence of an atmosphere or of other types of activity associated with comets
- 16. a meteorite composed primarily of iron and nickel
- 19. the large spherical region around the Sun from which most “new” comets come; a reservoir of objects with aphelia at about 50,000 AU