Astronomy~BW

2. the point in an orbit most distant from the body being orbited; the highest point
5. orbital point nearest the sun
6. a model of the universe in which Earth is at the center of the revolving planets and stars
10. the idea that the sun and planets formed together from a cloud of gas and dust, a nebula.
11. the line from the Sun to a planet sweeps out equal areas in equal times; explains where and when planets appear in the night sky
12. that planets move slower when they're farther from the Sun, and the influence that causes planets to go around the Sun weakens with distance
15. the universe began from one point billions of years ago and has been expanding ever since
18. an elongated circle, or oval shape, the shape of the planets orbit.
19. the effect of Earth wobbling on its axis (nutation).

1. the spinning motion of a planet on its axis
3. point in a planet's orbit that is farthest from the sun
4. the center of mass is the balance point between two orbiting bodies
7. the movement of an object around another object
8. the process or result of joining two or more things together to form a single entity
9. planets move around the Sun in an elliptical orbit with the Sun at one focus of the ellipse
13. a small, cyclic variation of the Earth's axis of rotation with a period of 18.6 years, caused by tidal forces; Earth wobbling on its axis
14. a model of the solar system in which Earth and the other planets revolve around the sun
16. the scientific study of the universe
17. point in an orbit that is closest to the earth