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Chapters Eighteen / Nineteen

Chapters Eighteen / Nineteen. Questions for the Day. What are stars born? How do stars evolve? How do stars die?. How are stars born?. Stars are born from interstellar medium. Disturbances from motion of the galaxy and other stars in the medium cause cores to form.

Melvin
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Chapters Eighteen / Nineteen

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  1. Chapters Eighteen / Nineteen

  2. Questions for the Day • What are stars born? • How do stars evolve? • How do stars die?

  3. How are stars born? • Stars are born from interstellar medium. • Disturbances from motion of the galaxy and other stars in the medium cause cores to form. • Proto-stars form from the cores. • Enough pressure causes the fusion.

  4. Interstellar Medium

  5. Views of a Molecular Cloud

  6. Steps of a Star Birth • Cloud Collapse • External Heating • Gravitational Disturbances • Core Formation • Unknown why clumps form. • Protostar Formation • Central section of cores collapse.

  7. Infrared Image of Molecular Cloud

  8. Core Collapse

  9. Protostar Formation

  10. Protostar Formation

  11. Young Stars • A star is considered a star when the core is producing fusion. • Types • Brown Dwarf: A Failed Young Star • Beta Pictoris: A Normal Young Star • T Tauri: An Active Young Star

  12. Brown Dwarf http://www.darkstar1.co.uk/dwarfs.jpg

  13. Young Stars

  14. Young Stars and The Main Sequence

  15. Young Star in the Orion Molecular Cloud

  16. T Tauri Jet of Material

  17. T Tauri Formation

  18. T Tauri and the Main Sequence

  19. Observations of the Solar System • The planets revolve counterclockwise around the sun; the sun rotates in the same direction. • The major planets, except Mercury and Pluto, have orbital inclinations close to the plane of the solar system. • Except for Mercury and Pluto, the planets move in orbits that are nearly circular.

  20. Observations (cont.) • Except for Venus, Uranus and Pluto, the planets rotate counterclockwise, in the same direction as their orbits. • The planet’s orbital distances from the sun follow a regular spacing. • Most satellites (moons) follow the same direction and lie close to the plane of the planet.

  21. Observations (cont.) • Some satellites follow the regular spacing rule. • Long-period comets come in all inclinations, but all other objects are fairly well behaved. • All Jovian planets have rings.

  22. Planet Formation around Young Stars

  23. Nebular-Accretion Hypothesis of Solar System Formation

  24. How do stars live/die? • Protostar • Nuclear Fusion • Main Sequence • Red Giant • Vertical Giant Branch (Mira Variables) • Horizontal Giant Branch (Cephied Variables)

  25. Stellar Evolution

  26. Evolution of a Star

  27. Ages of Stars http://zebu.uoregon.edu/~imamura/122/lecture-8/Open_isochrones.jpg

  28. Hertzsprung-Russel Diagram http://www.aw-bc.com/info/bennett/images/hrdiagram.jpg

  29. Relative Sizes of Different Types of Stars

  30. Structures of the Different Stellar Types

  31. Lifetimes of the Stars

  32. Energy Production in a Main Sequence Star

  33. Energy Production in a Red Giant

  34. Energy Production in a Red Supergiant

  35. Mira Variables http://www.daviddarling.info/encyclopedia/M/Mira_variable.html

  36. Henrietta Leavitt • 1868 – 1921 • Born in Lancaster, Massachusetts • Daughter of Congregational Church father • Graduated and went to work at Harvard a “computer”. http://upload.wikimedia.org/wikipedia/en/3/3b/Leavitt_aavso.jpg

  37. Henrietta Leavitt’s Work • Worked under Pickering along side Annie Jump Cannon. • In 1912, she published a study of variable stars in the Large Magellanic Cloud. • She found a Period-Luminosity relationship for Cephied Variable in the cloud.

  38. Cephied Variable Pulsation

  39. Instability Strip on Hertzsprung-Russell Diagram

  40. Variability of Cephieds

  41. Period – Luminosity Relationship of Cephieds

  42. Homework 9 • Describe the processes behind creating a star. • Describe the life time of both a B-type and M-type star. Why do they differ in their evolution. Defend the astronomical technique of studying star clusters. • Page 436 CQ 2, 7, 9, 16 Figure Based Question 1 • Page 462 CQ 8, 15, 20

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