Black Holes

2. the rate at which the position changes
5. solar mass
8. neutral subatomic particle
10. force that pulls objects towards each other
11. some have moons
12. anything we can touch, feel, sense, measure or detect
14. a very hot ball of super compressed of matter
17. a celestial body
19. the sun together with the group of celestial bodies that are held by its attraction and revolve around it
20. boundary where the sky seems to meet the ground or sea

1. used to track celestial objects
3. one-one thousandth of a second
4. any cyclic deformations of one astronomical body caused by the gravitational forces exerted by others
6. immense gravity
7. orbits the Earth
9. gravity pulls so much light can't get out
13. the outermost layer of a material or substance
15. saw Neptune in 1612
16. central or inner most part of the Earth
18. roomy enough to fit 1.3 million Earths inside it