1 / 28

Survey of the Universe Tom Burbine tburbine@mtholyoke

Survey of the Universe Tom Burbine tburbine@mtholyoke.edu. Quiz #4. This Wednesday Covers up to last Wednesday Cumulative You can bring in one 8 ½ by 11 inch piece of paper with anything written on it. Life of a Star.

Download Presentation

Survey of the Universe Tom Burbine tburbine@mtholyoke

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Survey of the UniverseTom Burbinetburbine@mtholyoke.edu

  2. Quiz #4 • This Wednesday • Covers up to last Wednesday • Cumulative • You can bring in one 8 ½ by 11 inch piece of paper with anything written on it

  3. Life of a Star • A star-forming interstellar cloud is called a molecular cloud because low temperatures allow Hydrogen to form Hydrogen molecules (H2) • Temperatures like 10-50 K • Contain Hydrogen and Helium with particles of silicates, carbon, and iron coated with irces

  4. Region is approximately 50 light years across

  5. Condensing • Molecular clouds tends to be lumpy • These lumps tend to condense into stars • That is why stars tend to be found in clusters

  6. Protostar • The dense cloud fragment gets hotter as it contracts • The cloud becomes denser and radiation cannot escape • The thermal pressure and gas temperature start to rise and rise • The dense cloud fragment becomes a protostar

  7. When does a protostar become a star • When the core temperatures reaches 10 million K, hydrogen fusion can start occurring

  8. http://www.youtube.com/watch?v=7YhRW9kLghY

  9. T-Tauri Stars • Pre-main-sequence stars that vary erratically in brightness

  10. Because nuclear reactions have not yet begun in the protostar’s core, this luminosity is due entirely to the release of gravitational energy as the protostar continues to shrink and material from the surrounding fragment

  11. http://www.youtube.com/watch?v=W13ZYepDBvo • http://www.youtube.com/watch?v=QFklLMB_ZOI&feature=related

  12. Brown Dwarfs • Failed stars • Not enough mass for fusion • Minimum mass of gas need for fusion is 0.08 solar masses (80 times the mass of Jupiter)

  13. Main Sequence • Is not an evolutionary track • Stars do not evolve on it • Stars stop on the main sequence and spend most of their lives on it

  14. Hydrostatic Equilbrium

  15. Fusion reaction in high mass -stars

  16. Main Sequence Lifetimes • The more massive a star on the main sequence, the shorter its lifetime • More massive stars do contain more hydrogen than smaller stars • However, the more massive stars have higher luminosities so they are using up their fuel at a much quicker rate than smaller stars

  17. Main Sequence Lifetime (t) • t = M/L x 1010 years • M is in Solar masses and L is in Solar Luminosities • For example, Sirius has a mass of 2 solar masses and a luminosity of 20 solar luminosities • t = (2/20) x 1010 years = 0.1 x 1010 years

  18. Ages • Universe is thought to be about 14 billion years old • So less massive stars have lifetimes longer than the age of the universe • More massive stars have ages much younger • So stars must be continually forming

  19. Blue stars have formed recently since they have young main sequence lifetimes

  20. Core Uses up hydrogen • When the core uses up its hydrogen • Gravity causes the core to shrink • The star leaves the main sequence

  21. Any Questions?

More Related