1 / 51

Announcements

Announcements. Exam Grades Wednesday March 31 Angel Grade update Friday April 2 Star Assignment 6, due Wednesday March 31 Do Angel quiz,. Objectives. Plot an Hertzsprung-Russell Diagram Locate the regions of giant, main sequence and white dwarf stars.

ramya
Download Presentation

Announcements

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. Announcements • Exam Grades Wednesday March 31 • Angel Grade update Friday April 2 • Star Assignment 6, due Wednesday March 31 • Do Angel quiz,

  2. Objectives • Plot an Hertzsprung-Russell Diagram • Locate the regions of giant, main sequence and white dwarf stars. • Describe the relations between surface temperature, luminosity, mass and size for these types of stars. • Describe the evolutionary state of the 16 brightest northern-hemisphere stars.

  3. What should we do with our information? • Luminosities • Surface Temperatures • Masses

  4. Number of Stars vs Luminosity 100 0.01 0.0001 1 HIGH Luminosity LOW

  5. Stellar Masses

  6. What should we do with our information? • Luminosities • Surface Temperatures • Masses Look for Relationships

  7. No Relationship

  8. Luminosity - Mass Relation L~M3.5

  9. HRDiagram:Luminosityvs.SurfaceTemperature

  10. Luminosity - Temperature Relation: Hertzsprung-Russell Diagram Luminosity->

  11. Recall:Hotter -> BrighterHotter -> BluerBigger -> BrighterThen cool+ Luminous-> Large Luminosity Temperature

  12. Recall:Hotter -> BrighterHotter -> BluerBigger -> BrighterThen small Luminosity+ Hot -> small Luminosity Temperature

  13. Stellar Size, Mass& HR Diagram

  14. Large radius Stars with low temperature and high luminosity must have large radius Small radius

  15. SUPERGIANTS Stars with low temperature and high luminosity must have large radius GIANTS WHITE DWARFS

  16. Most Low Mass stars haveSmallLuminosityMost Large Massstars haveLargeLuminosity High-Mass Stars Low-Mass Stars

  17. Regions of the H-R Diagram

  18. Activity • Answer the questions on your scantron sheet

  19. C B 1. Which star is the hottest? D Luminosity A Temperature

  20. C B 1. Which star is the hottest? A D Luminosity A Temperature

  21. C B 2. Which star is the most luminous? D Luminosity A Temperature

  22. C B 2. Which star is the most luminous? D C Luminosity A Temperature

  23. C B 3. Which star is a main-sequence star? D Luminosity A Temperature

  24. C B 3. Which star is a main-sequence star? D Luminosity A D Temperature

  25. C B 4. Which star has the largest radius? D Luminosity A Temperature

  26. C B 4. Which star has the largest radius? D Luminosity C A Temperature

  27. A 5. Which star is most like our Sun? D Luminosity B C Temperature

  28. A 5. Which star is most like our Sun? D B Luminosity B C Temperature

  29. HRDiagram BRIGHT HOT COOL FAINT

  30. Astronomy Place Questions 6. Spica is a Main Sequence star, having a surface temperature of 26,000K. In order for a star with a surface temperature of only 6,000K to have the same Luminosity as Spica, its radius must be? Luminosity = 4pR2sT4 If T ~ 4 x smaller, then R ~ 42 x larger = 16x

  31. 7. The rate of fusion (number of He nuclei produced per second) in the core of the star Vega (a main-sequence star with a temperature of about 10,000K is roughly? Lvega = 60 Lsun, so rate of energy generation = rate of energy loss is 60 x larger than Sun’s

  32. 8. A star having the same radius as the Sun, but a surface temperature 5 times higher than the Sun, would have a luminosity? L ~ T4 54 = 625

  33. 9. A main-sequence star that is twice as massive as the Sun will have a Luminosity? L ~ M3. 5 23 = 8, 24 = 16, so23.5 in between

  34. Lifetime on the Main Sequence How long will it be before MS stars run out of fuel? i.e. Hydrogen? How much fuel is there? M How fast is it consumed? L  M3.5 How long before it is used up? M/L = M/M3.5 = M-2.5

  35. Main SequenceLifetimes

  36. Lifetime on the Main Sequence • O & B Dwarfs burn fuel like a bus! • M Dwarfs burn fuel like a compact car! • Our Sun will last 1010 years on the Main Sequence • MS Lifetime  = 1010 yrs / M2.5

  37. Stars occur alone

  38. or in clusters

  39. another type of cluster

  40. Star Clusters • Stars approximately the SAME AGE • Stars approximately the SAME DISTANCE

  41. Cluster HR Diagrams Same Distance Same Age

  42. Pleiades now has no stars with life expectancy less than around 100 million years Main-sequence turnoff

  43. Detailed modeling of the oldest globular clusters reveals that they are about 13 billion years old

  44. ClusterAges

  45. Activity • Answer the questions on your scantron sheet

  46. A 6. Which of these stars will have changed the least 10 billion years from now? D Luminosity B C Temperature

  47. A 6. Which of these stars will have changed the least 10 billion years from now? D Luminosity B C C Temperature

  48. A 7. Which of these stars can be no more than 10 million years old? D Luminosity B C Temperature

  49. A 7. Which of these stars can be no more than 10 million years old? D Luminosity B A C Temperature

  50. A stars properties depend mostly on Mass Age

More Related