Chapter 31: Stars and Galaxies

2. distance light travels in one year - about 9.5 trillion km.
5. section of the H-R diagram that is plotted from the upper left to the lower right and constians 90 percent of all known stars.
6. late 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.
7. a region in space that is so dense that nothing can escape its inward pull of gravity.
8. telescope that collects and magnifies radio waves.
9. spiral galaxy that is about 100,00 light-years in diameter and contains from 200 to 400 billion stars, including the sun.
13. large group of stars, dust, and gas held together by gravity.
15. layer of the Sun that emits light into space.
16. giant star that has lost its outer layers, leaving behind a hot, dense core that continues to contract under gravity.

1. interstellar cloud of gas, ice and dust.
3. star pattern that appears to form images, is used by astronomers to locate and name stars, and often is named for a mythological figure.
4. produced by a collapsing star when protons and electrons in the star’s core collide to form neutrons.
10. group of about 50 galaxies including the Milky Way.
11. darker, cooler areas of the Sun’s photosphere.
12. device that disperses light into its component wavelengths, using a prism or diffraction grating.
14. gigantic explosion of a star in which the temperature within the collapsing star reaches 10 billion K, can evelole into a neutron star.