The Universe

8. Force that pulls matter closer together.
9. Dense remnant of star that can only be seen as an absence of light.
10. The lens that magnifies an image. (3,5)
12. Common issue of refracting telescopes, solved by using reflection.(9,10))
14. Another word for brightness.
17. Process by which Hydrogen becomes Helium.
18. The model of the solar system with the Earth at its center.
20. A type of electromagentic wave that is emitted by our Sun.
21. When a star runs out of energy and collapses, the rebounding material forms a massive explosion called.
22. A theory of how the universe started.
23. Evidence that galaxies are moving away from our own.

1. The model of the solar system with the Sun at its center.
2. Rapidly spinning neutron star.
3. Rings of gas and dust orbiting stars may condense to form what?
4. A giant cloud of gas and dust in space where stars form.
5. Type of star with an absolute magnitude +10 to +16 and temperature >4400 degrees celcius. (5,5)
6. What can be used to identify the elements in stars.(9,8)
7. The lens at the end of a refracting telescope that collects and focuses light to form an image.
11. What existed before the Big Bang?
13. Lipperhey developed what type of telescope?
15. Commonly used to measure distances in space. (5,4)
16. The apparent movement of stars when observed at different times of the year.
19. Another word for moon.