1. Chapter 17 Earth in Space
Vocabulary

3. the Sun and all the bodies that orbit it
Solar system
the Sun and all the bodies that orbit it

5. one full orbit of an object around another object
revolution
one full orbit of an object around another object

7. an imaginary center line around which the earth rotates
axis
an imaginary center line around which the earth rotates

9. one whole spin of an object on its axis
rotation
one whole spin of an object on its axis

11. a spacecraft that gathers data without a crew
space probe
a spacecraft that gathers data without a crew

13. a frozen mass of ice and dust orbiting the Sun
comet
a frozen mass of ice and dust orbiting the Sun

15. asteroid
a rocky mass up to several hundred kilometers wide that revolves around the Sun

17. an object in orbit around another object
satellite
an object in orbit around another object

19. Moon phase
An indication of the fraction of the Moon that is illuminated as seen from Earth