Chapter 26 Vocabulary

1. group/cluster of about 45 galaxies, including the Milky Way
4. surface of the Sun.
8. of how the universe began, what it is made of., and how it continues to evolve.
9. energy/energy that might be causing accelerated expansion of the universe.
10. telescope/optical instrument that uses double convex lenses to concave mirror to collect light and magnify an image.
12. stage in a star's life cycle that occurs when its hydrogen fuel is depleted, its core contracts, and its outer layers expand and cool.
14. sequence/section of an H-R diagram that is plotted from the upper left to the lower right and contains 90 percent of all known stars.
16. pattern that appears to form images, is used by astronomers to locate and name stars, and often is named for a mythological figure.
17. telescope/telescope that collects and magnifies radio waves.

1. light travels in one year-about 9.5 km
2. Bang Theory/the theory that the universe started with a big bang, or explosion, and has been expanding ever since.
3. dwarf/giant star that has lost its outer layers, leaving behind a hot, dense core that continues to contract under gravity.
5. that disperses light into its component wavelengths, using a prism or diffraction grating
6. group of stars, gas, and dust held together by gravity; most commonly can be elliptical, spiral, and irregular.
7. matter/unseen mass that adds to the gravity of a galaxy, but cannot be detected or seen.
11. telescope/optical instrument that uses double convex lenses to collect light and magnify and image.
13. darker areas of the Sun’s photosphere
15. mass/is a standard unit of mass in astronomy that is used to indicate the masses of other stars, as well as clusters, nebulae and galaxies.