astronomy key words - Lesson 12 - Our Galaxy: The Milky Way...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lesson 12 - Our Galaxy: The Milky Way Key Terms & Concepts Page references are keyed to the Horizons textbook, Exploring The Universe , 11e. 1. variable star: A star whose brightness changes periodically. (p. 234; video lesson; objective 1) 2. Cepheid variable star: Variable star with a period of up to 60 days. The period of variation is related to luminosity. (p. 236; video lesson; objective 1) 3. instability strip: The region of the H–R diagram in which stars are unstable to pulsation. A star passing through this strip becomes a variable star. (p. 236; objective 1) 4. RR Lyrae variable star: Variable star with a period of from 12 to 24 hours. Common in some globular clusters. (p. 236; objective 1) 5. period–luminosity relation: The relation between period of pulsation and intrinsic brightness among Cepheid variable stars. (p. 237; video lesson; objective 1) 6. proper motion: The rate at which a star moves across the sky. This rate is measured in seconds of arc per year. (p. 237; video lesson; objective 1) 7. calibrated: The establishment of the relationship between a parameter that is easily determined and a parameter that is more difficult to determine. (p. 237; objective 1) 8. Shapley–Curtis debate: A 1920 debate between Harlow Shapley and Heber Curtis on the nature of spiral nebulae. (p. 240; video lesson; objective 1) 9. disk component: All material confined to the plane of the galaxy. (p. 240; video lesson; objective 2) 10. kiloparsec (kpc): A unit of distance equal to 1000 pc or 3260 ly. (p. 240; objective 2) 11. spiral arm: Long spiral pattern of bright stars, star clusters, gas, and dust that extend from the center to the edge of the disk of spiral galaxies. (p. 241; video lesson; objective 2) 12. spherical component: The part of the galaxy including all matter in a spherical distribution around the center (the halo and nuclear bulge). (p. 241; video lesson; objective 2) 13. halo: The spherical region of a spiral galaxy, containing a thin scattering of stars,
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

astronomy key words - Lesson 12 - Our Galaxy: The Milky Way...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online