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Across 2. a rare event involving the explosion of a star 5. a cool giant star 7. developed the geocentric model of the solar system 9. a complete cycle of the ____ takes about 29.5 days 10. night and day are caused by this movement of the earth 11. a vehicle that is intended to carry humans into space 12. stars are composed of ____ and helium gases 13. different hemispheres have _____ seasons 16. theory that the universe began with all matter and energy concentrated in a very small object 19. type of galaxy with little dust and gas 21. the sudden brightening of a white dwarf 22. consists of all matter, energy and space 23. spacecraft that carries instuments to explore space 27. theory that states the universe is undergoing cycles of expansion and contraction 32. distance light travels in one year 33. the study of the universe 34. phases of the moon are caused by this 35. occurs when the moon passes into the shadow of the earth 36. an expanding shell of gas; stellar nursery 37. occurs when the moons shadow falls on the earth

Down 1. explained how gravity keeps the planets in order 2. an object launched into orbit; could be used with GPS 3. model of the solar system that we accept today (sun centered) 4. this diagram is used to classify stars 6. the model of the solar system that said it is earth centered 8. theory that states there never was a beginning and there will not be an end to the universe 14. the final stage of a white dwarf 15. type of galaxy we live in 17. our seasons are caused by this movement of the earth 18. developed the heliocentric model of the solar system 20. when it is summer in the southern hemisphere, it is ____ in the northern hemisphere 24. large groups of stars clustered together 25. developed the 3 models of planetary motion 26. a dying star that is slowly cooling off 28. the sun gets its energy through this process 29. Hubble announced that the universe was doing this 30. name of the galaxy we live in 31. tool used for observing the sky