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Across 4. Holds together Planets, Stars, and Galaxies 6. Main Sequence Star, 100 times bigger and 1000 times brighter than the sun (2 Words) 7. The twelve constellations found in the ecliptic. 9. Ninety percent of stars are found on this part of the Hertsprung-Russell Diagram (2 Words) 11. A Red Giant Star in Orion 12. Supernova remnant made entirely of neutrons (2 Words) 13. A young star that has recently collapsed from a stellar nebula 14. A bright nebula that is makes its own light (2 Words) 15. The galaxies near ours, up to 3 million light years away (2 Words) 16. After a blue giant star runs out of hydrogen, it expands to become this largest kind of star in the universe (2 Words) 20. After a red giant runs out of fuel and sheds its outer layers, this hot dense star remains (2 Words) 21. Dense cloud of gas and dust where new stars are born (2 Words) 22. Small, irregular galaxies in our Local Group (2 Words) 23. When a medium-sized main sequence star runs out of hydrogen, it expands to this and burns helium (2 Words)

Down 1. Violent explosion of a massive star, when the core collapses, visible for months 2. Great Bear Constellation (2 Words) 3. The most energetic kind of active galaxies , the central black hole has huge jets that travel near the speed of light 5. Found at the center of spiral and elliptical galaxies, with a mass of 100 million stars (2 Words) 8. Mostly empty, with clouds of gas and dust, between stars (2 Words) 10. Outer layers of a red giant, blown off when the helium is used up (2 Words) 17. Nearby Spiral galaxy, also known as M31 18. The moon of Saturn where the Hugyens probe landed in 2005 19. In a Main Sequence star, four hydrogen atoms fuse to make this element.