Vocabulary Extension 30.1

3. Any of the very large groups of stars and associated matter found throughout the universe.
5. Stars that have periods of pulsation between 1.5 hours and 1.2 days, and on average, they have the same luminosity.
8. A Spherical region where globular clusters are located.
10. Center of most galaxies.
12. Stars found in the halo and bulge and contain even smaller traces of heavy elements.

1. Stars that have pulsation periods between 1 and 100 days, and the luminosity increases as much as 100 times from the dimmest star the the brightest.
2. Stars located in the giant branch of the hertzspung-russell diagram, and pulsate in brightness.
4. Spiral regions of alternating density, which rotate as a rigid pattern.
6. Light year. Unit of length used to express astronomical distances.
7. Part of a galaxy made up of older, red stars.
9. Features of a galaxy and a part of a galaxy were hydrogen is concentrated.
11. Stars found in the disk and arms and have have small amounts of heavy elements.