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Special Stars

Special Stars. Take-Away Points. Variable Stars Multiple Stars. Variable Stars. How Identified R through Z (T Tauri) RR – ZZ, SS-SZ, etc. (RR Lyrae) AA-AZ, BB-BZ, etc. (FU Orionis) V + number (V1234 Sagitarii) Extrinsic: Variation not due to internal processes

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Special Stars

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  1. Special Stars

  2. Take-Away Points • Variable Stars • Multiple Stars

  3. Variable Stars • How Identified • R through Z (T Tauri) • RR – ZZ, SS-SZ, etc. (RR Lyrae) • AA-AZ, BB-BZ, etc. (FU Orionis) • V + number (V1234 Sagitarii) • Extrinsic: Variation not due to internal processes • Intrinsic: Variation due to internal processes

  4. Extrinsic Variables • Eclipsing Binaries • Rotating Variables • Ellipsoidal: Close binaries distorted by tidal forces. Cross-section varies as they rotate • Starspots: Stars have large brighter and dimmer areas

  5. Intrinsic Variables • Cepheids and Related Types • Stars Pulsate • As Star expands, its outer layers cool • Electrons combine with He atoms • Outer layers become more transparent • Star brightens • Easier escape of radiation allows star to contract • Long Period Variables • Red Giants and Supergiants • Pulsations controlled by ionization of H

  6. Dusty Stars • R Coronae Borealis • Mostly Constant Brightness • Occasionally Dim Dramatically • Cause: Carbon Dust Formation

  7. Catastrophic Variables • Flare Stars (Red Dwarfs) • Novae • Supernovae

  8. Eta Carinae

  9. Binary Stars • About 5% of Stars are multiple • Contact Binaries • Almost always eclipsing variables • Spectroscopic Binaries • Visual Double Stars • Hierarchical Multiple Stars • Trapezia: Still Evolving • Optical Doubles: Chance Alignment

  10. Hubble Image of Sirius

  11. Orbit of Sirius B

  12. Double Star

  13. Triple Star

  14. Lyra

  15. Lyra

  16. Epsilon Lyrae

  17. The Trapezium in Orion

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