Across
- 5. According to every standard model, the expansion of the universe is _____ _____ due to gravity. (two words - page 681)
- 10. A surprising discovery showed that the expansion of the universe is now _____. (page 681)
- 12. Stars that pulsate in brightness because of the expansion and contraction of their outer layers. (two words - page 663)
- 15. A possible outcome of the universe where the expansion slows to a halt in an infinite amount of time but never contracts. (page 680)
- 16. When the rate of expansion of the universe is known, it is possible to calculate the _____ since the expansion started and determine the _____ of the universe. (two words – page 679).
- 17. Type of wave that was used to determine the shape of the galaxy. (page 664)
- 20. Measured the redshift and distances of many galaxies and found that the farther away a galaxy is, the faster it is moving away. (page 674)
- 21. Type of variable star with a pulsation period of 1 to 100 days. (two words - page 664)
- 22. If the universe is expanding now, it must have been _____ and _____ in the past. (two words – page 675)
- 23. The study of the universe – its nature, origin, and evolution is called _____. (page 679)
- 27. Type of galaxies that do not have a distinct shape. (page 673)
- 28. The stars found in the halo and buldge and contain even smaller amounts of heavy elements (two words – 667)
- 30. Galaxies that emit large amounts of energy from their cores are called _____ galaxies. (page 675)
Down
- 1. The stars found in the disk and arms that have small amounts of heavy elements. (two words – page 667)
- 2. The age of the universe is 13.7 _____ years. (page 679)
- 3. Determining Hubble’s Constant (H) is a difficult task because it is hard to measure accurate distances to the most remote _____. (page 675)
- 4. The theory that the universe began as a point and has been expanding ever since is called _____ (two words – page 679)
- 6. The name of a small cluster of galaxies that the Milky Way belongs to. (two words – 673)
- 7. Type of galaxies that are not flattened into disks and do not have spiral arms. (page 671)
- 8. By making a graph comparing a galaxy’s _____ to the _____ at which it is moving, Hubble determined that the universe is expanding. (page 675)
- 9. Located at the center of most galaxies, they can weigh in at a few million to a few billion times the mass of the Sun. (three words – page 666)
- 11. Persistent background noise that appears to come from all directions. (three words – page 680)
- 13. Type of galaxy that are extremely luminous and are often giant elliptical galaxies that emit as much energy in radio wavelengths as they do in wavelengths of visible light. (page 676)
- 14. The short-wavelength radiation that filled the universe 300,000 years after it formed expanded into radiation in the form of _____. (page 680)
- 18. A possible outcome of the universe where the expansion will never stop. (page 680)
- 19. Thought to be made up of a form of subatomic particle that interacts only weakly with other matter and is found in all galaxies. (two words – page 671)
- 24. Type of galaxies that are disklike and contain spiral arms. (page 671)
- 25. The label astronomers have given to the reason of the acceleration of the universe. (two words – page 681)
- 26. A possible outcome of the universe where the expansion stops and becomes a contraction. (page 680)
- 29. Starlike objects with emission lines in their spectra. (page 676)